Advanced Breast Cancer Patients Research Articles

Everolimus plus endocrine therapy beyond CDK4/6 inhibitors progression for HR+ /HER2- advanced breast cancer: a real-world evidence cohort.

Everolimus in combination with endocrine therapy (ET) was formerly approved as 2nd-line therapy in HR(+)/HER2(-) advanced breast cancer (aBC) patients (pts) progressing during or after a non-steroidal aromatase inhibitor (NSAI). Since this approval, the treatment landscape of aBC has changed dramatically, particularly with the arrival of CDK 4-6 inhibitors. Endocrine monotherapy after progression to CDK4/6 inhibitors has shown a limited progression-free survival (PFS), below 3months. Evidence of the efficacy of everolimus plus ET after CDK4/6 inhibitors is scarce. A retrospective observational study of patients with aBC treated with everolimus and ET beyond CDK4/6-i progression compiled from February 2015 to December 2022 in 4 Spanish hospitals was performed. Clinical and demographic data were collected from medical records. The main objective was to estimate the median progression-free survival (mPFS). Everolimus adverse events (AE) were registered. Quantitative variables were summarized with medians; qualitative variables with proportions and the Kaplan-Meier method were used for survival estimates. One hundred sixty-one patients received everolimus plus ET (exemestane: 96, fulvestrant: 54, tamoxifen: 10, unknown: 1) after progressing on a CDK4/6 inhibitor. The median follow-up time was 15months (interquartile range: 1-56months). The median age at diagnosis was 49years (range: 35-90years). The estimated mPFS was 6.0months (95%CI 5.3-7.8months). PFS was longer in patients with previous CDK4/6 inhibitor therapy lasting for > 18months (8.7months, 95%CI 6.6-11.3months), in patients w/o visceral metastases (8.0months, 95%CI 5.8-10.5months), and chemotherapy-naïve in the metastatic setting (7.2months, 95%CI 5.9-8.4months). This retrospective analysis cohort of everolimus plus ET in mBC patients previously treated with a CDK4/6 inhibitor suggests a longer estimated mPFS when compared with the mPFS with ET monotherapy obtained from current randomized clinical data. Everolimus plus ET may be considered as a valid control arm in novel clinical trial designs.

Abstract PO4-16-07: Cyclin-dependent kinase inhibitor plus endocrine therapy in HR+/HER2- invasive breast cancer with bone marrow and pancytopenia: a new standard of care? Collaborative multicentric Argentinean real-world study (SUMA-02)

Abstract Introduction Bone marrow involvement is a rare occurrence in patients with advanced breast cancer (ABC), and the prognosis in this context is generally poor. Prompt initiation of treatment to improve the patient's hematological status is crucial. However, this condition is often excluded from clinical trials, making it challenging to determine the effectiveness of new drugs. Limited data and evidence are available to guide treatment decisions, but guidelines recommend starting with chemotherapy for the need of a rapid response. This study aims to analyze the real-world efficacy of cyclin-dependent kinase inhibitors (CDKis) in HR+/HER2- ABC with bone marrow infiltration. Methods Retrospective multicenter cohort study including HR+/HER2- ABC patients from public and private facilities in Argentina. Patients with confirmed bone marrow involvement (blood smear or histological biopsy analysis) and treated with CDKi were eligible. Bone marrow response was defined as an increase in at least one of the previously abnormal blood series to Hb >10.0, platelets >100,000, and leukocytes >4,000. Results A total of 22 patients from different medical centers in Argentina were included. The median age was 55.5 (IQR 46.25-65). Histological confirmation of bone marrow involvement was reported in 81.8% (18) of patients. Among them, 54.5% (12) had initial diagnosis at an early stage, and 13.6% (3) experienced relapse during or within 1 year of completing adjuvant hormonal treatment. Bone-only metastasis was observed in 50% (11) of patients, while the remaining 50% (11) had both visceral and bone disease. Anemia, thrombocytopenia, and leukopenia were present in 95.5% (21), 90.9% (20), and 40.9% (9) of patients, respectively. In 68.2% (15) of patients, bone marrow involvement was detected at the first-line treatment setting. The selected CDKis were palbociclib in 40.9% (9) of patients, ribociclib in 31.8% (7), and abemaciclib in 27.3% (6). The bone marrow response rate was 68.2% (15), with a median of 2 cycles (range 1-5) required for a response. Dose reduction was necessary in 31.8% (7) of patients. Discussion Managing patients with uncommon sites of metastasis, such as bone marrow, poses significant challenges for oncologists. Bone marrow infiltration leads to hematopoietic alterations that adversely affect the quality of life, resulting in increased risk of infections, bleeding, and other comorbidities with fatal consequences. While chemotherapy is the standard treatment in such cases, our study demonstrates that CDKis are a safe and effective option for managing these complications. Conclusion The findings of this study support the evaluation of CDKis as a standard treatment for HR+/HER2- ABC patients. Our results are in line with the recently published phase 2 clinical trial RIGHT CHOICE, which showed a prolonged progression free survival in patients treated with ribociclib and HT with HR+/HE2- ABC and visceral crisis. Citation Format: Alexis Ostinelli, Pablo Mandó, Carolina Almada, Melina Winocur, M. Agustina Ipiña, Viviana Paez, Silvia Aparicio, Sergio Rivero, Federico Waisberg, Laura Sabina Lapuchesky, Cristian Micheri, M. Belen Montenegro, Cristina Rusz Maidana, Carolina Reinhardt, Evelina Rovera, Gonzalo Gómez Abuin, Santiago Bella, Florencia Perazzo, Adrian Nervo, Andrea Aguilar, Matías Chacón, Victoria Costanzo, Valeria Caceres, Jorge Nadal. Cyclin-dependent kinase inhibitor plus endocrine therapy in HR+/HER2- invasive breast cancer with bone marrow and pancytopenia: a new standard of care? Collaborative multicentric Argentinean real-world study (SUMA-02) [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-16-07.

Abstract PO4-05-04: Comparative effectiveness of Palbociclib plus Aromatase inhibitor versus fulvestrant alone as initial endocrine therapy for HR+/HER2- advanced breast cancer in Chinese clinical practice: a real-world study

Abstract Background: In the real world, there are still a large number of HR+/HER2- advanced breast cancer patients receiving initial endocrine therapy with fulvestrant monotherapy in China, especially patients with bone metastases only. It is due to lack of data comparing the effective between Palbociclib combined with AI and fulvestrant monotherapy as initial endocrine therapy. On the other hand, there are economic factors and access issues. According to the National Cancer Center's previous clinical experience, Palbociclib combined with AI is superior to fulvestrant monotherapy in HR+/HER2- advanced breast cancer patients receiving initial endocrine therapy. Therefore, we collected and summarized the previous clinical data in our center to compare the effective of Palbociclib combined with AI and fulvestrant monotherapy for HR+/HER2-advanced breast cancer patients receiving initial endocrine therapy in China. Patients and methods: This is a retrospective real-world study of multicenter studies. It aimed at verifying the effective of Palbociclib combined with AI and fulvestrant monotherapy for HR+/HER2-advanced breast cancer patients receiving initial endocrine therapy in China. A total of 392 patients with ≥3 months of follow-up received Palbociclib plus AI or fulvestrant alone in the first-line setting between April 1, 2015 and February 1, 2023. Stabilized inverse probability treatment weighting (sIPTW) was used to balance baseline demographic and clinical characteristics. Real-world progression-free survival (rwPFS) and overall survival (OS) were analyzed. Results: After sIPTW adjustment, a median follow-up of 37 months (range 34-40) in the Palbociclib group and 59 months (range 56-61) in those taking fulvestrant alone. Palbociclib combination regiment was associated with significantly longer median rwPFS compared to fulvestrant alone (22.0 vs 14.0 months; HR,0.469;95% CI 0.370–0.594, p< 0·0001). Median OS was not reached in the Palbociclib group and was 57 months (95% CI 54.0–66.0) in the fulvestrant group(HR,0.666; 95% CI 0.437–1.017, p< 0·94). Conclusion: In the real-world population of patients, palbociclib combined with AI endocrine therapy is superior to fulvestrant monotherapy in HR+/HER2- advanced breast cancer patients receiving initial endocrine therapy. PFS and OS before IPTW PFS and OS after IPTW Table patient characteristics Citation Format: Jian Yue, Xue Wang, Jie Ju, Zixiang Yang, Tong Wei, Peng Yuan, Min Gao, Ling Xu, Yin Guan. Comparative effectiveness of Palbociclib plus Aromatase inhibitor versus fulvestrant alone as initial endocrine therapy for HR+/HER2- advanced breast cancer in Chinese clinical practice: a real-world study [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-05-04.

Abstract PO4-05-05: Immune Activation Signatures for predicting CDKi primary response in advanced breast cancer patients

Abstract Background Cyclin Dependent Kinase inhibitors (CDKi’s) in combination with Endocrine Therapy (ET) have changed the first line management of patients with the most common subtype (HR+, HER2-) of metastatic breast cancer (MBC), improving progression-free survival (PFS) and overall survival. However, in approved indications for advanced breast cancer, approximately 20% of patients have been observed to have no response to CDKi’s and ET, and to progress after starting these therapies. Unlike other targeted therapeutics, there is no companion diagnostic or other clinically reliable biomarker for clinical decision support to indicate which patients will and will not benefit from CDKi therapy. Methods We have developed a novel platform that measures the Immune Activation Signature of patient plasma samples. Via simple measurements of the total concentration of protein-incorporated amino acid residues within patient plasma samples, the platform is designed to reveal changes in the proportion of immunoglobulins and albumin, and class-switching among immunoglobulins. For that purpose, we use Bioorthogonal chemical labelling reactions to label the protein-incorporated amino acids residues within the plasma. We measured the plasma samples of N=30 HR+, HER2- MBC patients, median age 54 years old, who were baseline naïve for CDKi’s treatment (16 on palbociclib, 11 on ribociclib, and 3 on abemaciclib) and ET. Eighteen patients had metastatic visceral disease and 12 patients had bone-only MBC. All patients were prospectively followed, and response assessed according to RECIST criteria on a CT scan every 3-months. Results Non-responding patients developed objective progressive disease during the first 6 months after starting CDKis and ET. In this cohort, 4 patients (13%) were classified as non-responders. The median PFS in non-responding patients was 4.5 months (4.03-5.02) and the median PFS in the cohort of responding patients was 16.6 months (6.8 – 40.9). The Immune Activation Signatures of the Responding and Non-Responding patients are shown in table 1. We analyzed the results with classical statistics and machine learning. A multivariate analysis of variance (MANOVA) test of the null hypothesis that the Immune Activation Signatures of Non-Responders and Responders are the same gave p = 0.00388. We analyzed the measured Immune Activation Signatures using a supervised machine learning classifier and observed in a held-back validation set correct prediction of 100% of non-responding patients and 95% accurate predictions overall. Conclusions According to these results, this platform may provide a clinically helpful biomarker for clinical decision support in the advanced or aggressive breast cancer context (patients with visceral metastasis bordering on visceral crisis), or for patient stratification in new indications. Table. Immune Activation Signature measurements (mean values in Clinical Outcome) Citation Format: Luis Costa, Cong Tang, Emma Yates, Qi Shi, Wesley Sukdao, Patricia Corredeira, Gonçalo Costa, Helena Pais, Catarina Abreu, Leonor Ribeiro, Rita Teixeira de Sousa, Sofia Torres, André Mansinho, Sandra Casimiro, Ana Cavaco, Patricia Alves, Angela Rodrigues, Lisiana Szeneszi, Gonçalo Bernardes. Immune Activation Signatures for predicting CDKi primary response in advanced breast cancer patients [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-05-05.

Abstract PO1-14-01: Clonal Architecture of circulating tumor DNA predicts Early Progression on Tamoxifen With or Without Palbociclib in Hormone Receptor-Positive Advanced Breast Cancer: NCCH1607/PATHWAY trial

Abstract Objective: Some patients with poor prognosis hormone receptor-positive, human epidermal growth factor receptor 2-negative (HR+/HER2-) advanced breast cancer (ABC) experience early disease progression on the combination of CDK4/6 inhibitors and endocrine therapy. We aimed to determine whether clonal architecture assessed by circulating tumor DNA (ctDNA) could identify patients at higher risk of early progression on tamoxifen therapy with or without palbociclib. Methods: PATHWAY trial is a randomized, placebo-controlled, Asian international, double-blind, phase 3 study evaluating palbociclib plus tamoxifen (PAL+TAM) versus placebo plus tamoxifen (PLB+TAM) in pre/perimenopausal and postmenopausal women with HR+/HER2- ABC (NCT03423199). The study was conducted as a Clinical Research Collaboration with the National Cancer Center Hospital as the regulatory study sponsor and Pfizer providing drug and financial support. The primary endpoint was investigator assessed progression-free survival (PFS). Genomic profiling by next-generation sequencing was an exploratory endpoint to characterize molecular alterations in ctDNA and correlate these with clinical outcomes. Plasma samples were collected at cycle 1-day 1 (pre-treatment) and cycle 2-day 15 and sequenced with the Guardant360 assay (Guardant Health). Patients were included if they had a minimum of 14 days of treatment in the first cycle. The variant allele frequency (VAF) was defined as number of mutant molecules at a specific nucleotide location over the total number of molecules present in the background at a specific given genomic location. We assessed the gene with highest VAF as the dominant clone allele frequency (DCAF). The association of changes in ctDNA alterations with PFS was evaluated to identify biomarkers of early progression. Results: Pre-treatment plasma was successfully sequenced in 177 of the 184 patients; 88 patients treated with PAL+TAM, and 89 with PLB+TAM. ctDNA was detected in 144 (81.4%) patients; the median number of genetic abnormalities was 2 (range, 0-19). PIK3CA, TP53, ERBB2, ESR1, AKT1, EGFR and PTEN were the genes with highest VAF as the dominant clone (24.3%, 11.9%, 4.5%, 4.5%, 3.4%, 3.4%, 3.4%, respectively). The median DCAF was 1.79 (range, 0.1-81.23); PAL+TAM, 2.53 (range, 0.1-63.5) and PLB+TAM, 1.65 (range, 0.08-81.23). Patients with ≥ 2 detectable genomic alterations and DCAF ≥ 1.8% had worse PFS (hazard ratio (HR) 1.93 [95% confidence interval (CI): 1.375 to 2.721], p = 0.0003 and HR 1.95 [95% CI: 1.345 to 2.834], p < 0.0001, respectively) compared to all other patients. In addition, we evaluated whether changes of clonal architecture in ctDNA at early treatment time point (ie. Cycle 2 Day 15) are associated with PFS. Patients with increased DCAF had worse PFS on both PAL+TAM (HR 2.80 [95% CI: 0.552 to 14.15], p = 0.04) and PLB+TAM (HR 2.02 [95% CI: 1.022 to 3.990], p = 0.01). All patients with high pretreatment DCAF (≥ 1.8%) and increase in DCAF progressed within 1 year (n=5, 2 patients treated with PAL+TAM, and 3 with PLB+TAM). Conclusion: Evaluation of clonal architecture in ctDNA could support identification of HR+/HER2- ABC patients with poorer prognosis, who may be at higher risk of early progression, regardless of CDK4/6 inhibitor use. Citation Format: Yoon-Sim Yap, Yuki Kojima, Akinobu Hamada, Hirofumi Mukai, Yen-Shen Lu, Joo Hyuk Sohn, Yoshiko Umeyama, Emi Noguchi, Kazuki Sudo, Tomomi Hata, Aya Kuchiba, Taro Shibata, Shigehiro Yagishita, Masayuki Yoshida, Shinji Kohsaka, Kouya Shiraishi, Kenichi Nakamura, Kenji Tamura, Kan Yonemori. Clonal Architecture of circulating tumor DNA predicts Early Progression on Tamoxifen With or Without Palbociclib in Hormone Receptor-Positive Advanced Breast Cancer: NCCH1607/PATHWAY trial [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-14-01.

Abstract PO3-25-11: Unprecedented responses to neoadjuvant sequential administration of Tocilizumab followed by cisplatin/docetaxel for locally advanced triple negative breast cancer patients

Abstract Background: Triple negative breast cancer (TNBC) remains a challenge for clinicians due to its aggressive behavior and scarcity of effective treatment. Interleukin 6 (IL-6) is well known to contribute to poor therapeutic gain, tumor relapse and aggressive tumor growth. Here we have explored targeting the IL-6 signaling pathway by Tocilizumab (Actemra) as a new potential therapeutic approach for the treatment of TNBC. Methods: The study population includes thirty (30) patients with (T2-T4, N0-3) stage (IIB-III) TNBC treated uniformly with Tocilizumab followed with cisplatin/docetaxel according to a traditional 3+3 design using a sentinel patient at each cohort. Eligible patients received Tocilizumab on day 1 followed by cisplatin/docetaxel on day 2 every 4 weeks for a total of six cycles. The primary end points were pathological complete response in breast and axilla (pCR) (ypT0/ypN0) and assessment for tolerability/toxicities profiles. Additionally, the status of the BRCA1 and BRCA2 genes was determined in all patients. Results: Eligible patients who were enrolled in this phase I/II trial had a median age of 42 years, with 63% premenopausal and 67% had nodal involvement at base line. The median tumor size was 45 mm (range 25-150 mm), stage III A/B 26% and stage IIIC 50%. Germline BRCA1/2 mutations represented 27%. The overall pCR and (RCB class 0+1) were 66% and 69%, respectively. Interestingly, pCR reached 81% in axilla, and 100% in patients with tumors bearing BRCA1/2 mutations. Interestingly, tocilizumab affected the blood level of several pro-carcinogenic cytokines. Conclusions: To our knowledge this novel therapeutic strategy is the first to report the inhibition of a cytokine signaling (a new class of biological therapy) in combination with chemotherapy for the intricate and hard-to-treat TNBC patients with unprecedented responses and acceptable tolerability/toxicities, which merits further investigation. Pending Patents: US Patent Application No. 18/122,839 European Patent Application No. 23 162 694.6 Citation Format: Taher Al-Tweigeri, Noura Alraouji, Asma Tulbah, Syed Akhtar, Meshari Alzahrani, Saleh Najjar, Dahish Ajarim, Kauser Suleman, Adher Al Sayed, Abdelilah Aboussekhra. Unprecedented responses to neoadjuvant sequential administration of Tocilizumab followed by cisplatin/docetaxel for locally advanced triple negative breast cancer patients [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-25-11.

Abstract PO4-05-03: Cell-free tumor DNA analysis in advanced or metastatic breast cancer patients enrolled in the German registry study PRAEGNANT

Abstract Background Accurate molecular profiling is crucial for optimal treatment decisions in advanced or metastatic breast cancer. Liquid biopsies, such as circulating cell-free tumor DNA (cfDNA, cftDNA or ctDNA), provide a non-invasive approach to monitor molecular alterations in the tumor. The German PRAEGNANT registry study aims to investigate such molecular biomarkers for precision medicine and their practical integration into clinical practice. In this context, cftDNA testing was performed as part of a PRAEGNANT research subproject, with the objectives of understanding the physician's rationale for initiating cftDNA testing, identifying detected alterations, and assessing the clinical impact of the associated findings Methods Patients with advanced or metastatic breast cancer were prospectively enrolled in the PRAEGNANT registry study (NCT02338167). The decision to undergo cftDNA testing was based on the physician's discretion. Blood samples were collected using Streck cfDNA BCT tubes and sent to the GUARDANT Health central laboratory for cftDNA extraction and subsequent next-generation sequencing analysis, employing the FDA-approved GUARDANT360 CDx test, a 74 gene panel including all guideline-recommended biomarkers, including single nucleotide variants (SNVs), indels, fusions and amplifications. Recruitment of patients occurred at four PRAEGNANT study centers between April 2022 and July 2023. The GUARDANT360 CDx report, along with a questionnaire regarding the testing intent and clinical impact of the results, was provided to the treating physician. Results 46 patients were eligible for analysis as per clinical characteristics. CftDNA analysis was successfully performed for all 46 cases. 38 (83%) harbored at least one somatic alteration in the analyzed genes. Fifteen patients (33%) harbored alterations in TP53, thirteen (28%) in PIK3CA. Five patients (11%) harbored mutations in ESR1. Somatic mutations in BRCA1 or BRCA2 were detected for five (11%) and six (13%) patients, respectively. One BRCA2 mutation was categorized as synonymous and one BRCA2 and three BRCA1 alterations as variants of uncertain significance. Eight patients (17%) harbored mutations in ATM. Most patients included were HR+HER2- (N=27, 58%). In this subgroup, eight (30%) patients had a PIK3CA alteration, five (19%) with an indication for treatment with alpelisib, eight (30%) a mutation in ATM, BRCA1 or BRCA2 and four (15%) in ESR1. Questionnaires regarding intention of testing and clinical impact were completed by 43 treating physicians (93%). Among them, 33% of patients had current indications for PARP inhibitor treatment, and 61% would consider it at the next change of therapy if a BRCA1 or BRCA2 mutation was detected. Additionally, 21% of patients had a current indication for alpelisib treatment if a relevant PIK3CA mutation was found, and 58% would consider it in the next line of treatment. Overall, cfDNA testing influenced the current or future treatment decisions in 35% of patients. Discussion The high prevalence of somatic alterations in TP53, PIK3CA, ESR1, and BRCA1/2 genes, identified through cftDNA testing with GUARDANT360 CDx, highlights their potential as biomarkers for targeted therapies in advanced/metastatic breast cancer. Detection of specific mutations influenced treatment decisions, such as eligibility for alpelisib or PARP inhibitors and might further facilitate treatment with elacestrant in future treatment lines after its approval in Germany. These findings demonstrate the clinical impact of cftDNA testing in guiding personalized treatment selection. Additionally, the identification of such somatic alterations within a registry study like PRAEGNANT presents a unique opportunity to consider enrolling these patients into biomarker-guided clinical trials. Citation Format: Hanna Hübner, Pauline Wimberger, Elena Laakmann, Eugen Ruckhäberle, Matthias Ruebner, Theresa Link, Erik Belleville, Iris Faull, Marcus Hausch, Diethelm Wallwiener, Andreas Schneeweiss, Hans Tesch, Sara Brucker, Peter A. Fasching, Volkmar Müller, Tanja Fehm. Cell-free tumor DNA analysis in advanced or metastatic breast cancer patients enrolled in the German registry study PRAEGNANT [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-05-03.

Abstract PO1-16-11: Real-world features and outcomes of young advanced breast cancer (ABC) patients (pts) from RegistEM (GEICAM/2014-03) study

Abstract Background: BC is the most incident cancer worldwide in < 40 years old (y) women. Increasing body mass index and changes in reproductive history contribute to the growing incidence of premenopausal BC. A higher proportion of luminal B-like and estrogen receptor negative (ER─) tumors, an increased risk of early relapse, and more unfavorable longer-term outcomes for young women with ER+ tumors when compared to older women, have been reported. In this analysis, we focus on age-specific BC characterization from a real-world population-based perspective. Methods: Pts were enrolled in the non-interventional and ambispective RegistEM study in ABC diagnosed between 2016 and 2019. We describe the features and outcomes of < 50 y pts at their initial BC diagnosis according to their BC subtype. BC subtypes were based on the most recent tumor tissue sample (distant metastasis, and in its absence, primary BC). Comparisons between < 40 and ≥ 50 y groups were performed. Results: Pts < 50 y represent 39% (n=685) of total pts with available data (n=1739, any age group) in the registry. By age, 12% (n=212) were < 40y, and 27% (n=473) 40-49y. At first BC diagnosis, 75% and 25% pts had early BC (EBC) and de novo metastatic BC (MBC), respectively. In EBC pts, stage II (50%) and III (28%) were the most frequent at diagnosis; invasive non-special type carcinoma was the predominant morphology, and grade 2 was the most common histological grade, but grade 3 was predominant in TN pts and HER2+ < 40y pts. The median time to recurrence was < 2y in TN pts, 3y in HER2+ pts, and 6y in luminal HER2─ pts. At ABC diagnosis, the median age was 47y, all pts were female but one, 98% white, and 60% premenopausal (94% were premenopausal at EBC diagnosis). A family history of BC and/or ovarian cancer was reported in 34% pts, and a hereditary-risk genetic test was performed in 39% (254 of 652) pts; 12% (n=30) had BRCA1/2 mutations, with a proportion higher in TN pts (9 of 33, 27%) vs. luminal HER2─ (21 of 183, 12%) and HER2+ (0 of 38) pts. Visceral disease was the most frequent in all subgroups, highlighting statistical differences (p=0.022) between age groups ( < 40y 55% vs. ≥50y 71%) only in TN pts. 60% had ≤ 2 locations involved, similarly in all subgroups. The presence of >2 metastatic locations was statistically higher in HER2+ pts ≥50y (54%) vs both < 40y (32%) and 40-49y (48%). Brain disease was more present at ABC diagnosis in TN (9%) and HER2+ (7%) than in luminal HER2─ (3%). Median no. of treatment lines (L) was 3 (range 0-11), and median follow-up 44 mo (95% CI: 41-44). 99% pts received 1L, the distribution of treatments by BC subtype within each age subgroup was similar; median duration of 1L was 21 months (mo) in luminal HER2─, 17 mo in HER2+, and 5 mo in TN pts. 68% of pts who received 1L, reached 2L. Duration of 2L dropped dramatically: 8 mo in luminal HER2─, 6 mo in HER2+, and 2 mo in TN pts. No differences between ≥50y and the rest of pts were observed in PFS for any treatment line. 49% pts had died at the database cut-off date (05-April-23), with no differences between age groups, but TN pts had the highest death rate (80%). Additional data according to BC subtypes and age groups are in the table. Conclusions: Luminal HER2─ was the predominant BC subtype in all age subgroups. Visceral disease was more prevalent in young TN pts compared to older pts. TNBC pts experienced a shorter median time to recurrence and the highest mortality rate regardless of age, compared to HER2+ and luminal HER2- pts, indicating the need for targeted interventions in this subgroup. Citation Format: Sara López-Tarruella, Angel Guerrero, Isabel Álvarez, Silvia Antolin Novoa, Ariadna Tibau, Josefina Cruz, César A Rodríguez, Purificación Martínez, J. Ignacio Chacón, María Hernández, Mireia Margelí, Encarna Adrover, Catalina Falo, Iria González, Álvaro Rodríguez-Lescure, María Marín, César Gómez, Juan de la Haba-Rodríguez, J. José Illaramendi, Raquel Andrés, Andrea Blasco, Mª José Escudero, Susana Bezares, Federico Rojo. Real-world features and outcomes of young advanced breast cancer (ABC) patients (pts) from RegistEM (GEICAM/2014-03) study [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-16-11.

Abstract PS15-04: A Phase 1b/2 study of palazestrant (OP-1250), an oral complete estrogen receptor antagonist (CERAN) and selective ER degrader (SERD), with palbociclib in ER-positive, HER2-negative, advanced or metastatic breast cancer patients

Abstract Background: Palazestrant (OP-1250) is a small molecule oral complete estrogen receptor (ER) antagonist (CERAN) and selective ER degrader (SERD) that binds the ligand binding domain of ER and completely blocks ER-driven transcriptional activity in both wild-type (ESR1-wt) and mutant (ESR1-mut) forms of ER. In preclinical studies, palazestrant demonstrated improved tumor growth inhibition and shrinkage when combined with a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor. In a Phase 1/2 monotherapy clinical study in patients with ER-positive, human epidermal growth factor receptor 2-negative metastatic breast cancer, palazestrant was well tolerated with demonstrated antitumor efficacy and favorable pharmacokinetics (PK) supporting once a day (qd) dosing at the recommended Phase 2 dose of 120 mg. In this study, pts received palazestrant at escalating doses of 30, 60, 90, and 120 mg qd in combination with palbociclib (125 mg qd) and no dose-limiting toxicities were observed. Palazestrant did not affect palbociclib PK and no drug–drug interactions (DDIs) occurred. Here we report updates on safety, efficacy, and PK from the ongoing study of palazestrant in combination with palbociclib. Methods: Patients with advanced or metastatic breast cancer with progression on or after ≤1 line of endocrine therapy (prior CDK4/6 inhibitor therapy and ≤1 chemotherapy allowed) were enrolled to receive oral palazestrant 120 mg qd with oral palbociclib 125 mg qd for 21 of 28 days (NCT0526610). Results: As of May 12, 2023, 33 patients have been treated with palazestrant in combination with palbociclib; 12 pts were dosed in the dose-escalation phase and 21 patients were dosed in the dose-expansion phase of the study. Twenty-two patients (67%) received prior CDK4/6 inhibitor therapy; 15 patients received prior palbociclib. Thirteen of 25 patients (52%) with available baseline ctDNA had an ESR1 mutation. The most common (≥20%) treatment-emergent adverse events (TEAEs) were neutropenia, nausea, vomiting, constipation, and diarrhea. Most of these events were grade 1 or 2. The most common grade 3 or 4 related AE was neutropenia (18/33 [55%] were grade 3; 3/33 [9%] were grade 4). The steady-state exposure of palazestrant when dosed with 125 mg palbociclib was consistent with the monotherapy study. Palbociclib exposure at steady-state was comparable to published monotherapy data when combined with palazestrant at all dose levels tested. As of the data cut-off, there were 4 partial responses (2 confirmed) out of 19 response-evaluable patients, with a clinical benefit rate (CBR) of 42% (8/19) across all patients and 67% (6/9) in patients with ESR1 mutations. Conclusions: Palazestrant and palbociclib dosed in combination were well tolerated with a safety profile consistent with the individual profiles of each drug as monotherapy, and there were no DDIs. Tumor responses and clinical benefit were observed in this population of patients, including those who received prior CDK4/6 inhibitors. Expanding on our previous report, these data provide the rationale to continue advancing the clinical development of palazestrant with the approved dose of palbociclib. Updated data will be presented. Citation Format: Arlene Chan, Daphne Day, Phuong Dinh, Michael Slancar, Janine Lombard, Vinod Ganju, Nicole McCarthy, Rosalind Wilson, Demiana Faltaos, Gurpreet Mathauda-Sahota, Caitlin Murphy. A Phase 1b/2 study of palazestrant (OP-1250), an oral complete estrogen receptor antagonist (CERAN) and selective ER degrader (SERD), with palbociclib in ER-positive, HER2-negative, advanced or metastatic breast cancer patients [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS15-04.

Abstract PO4-06-06: Clinical Implications of Body Mass Index (BMI) in BRCA-associated Advanced Breast Cancer Patients Treated With PARP (Poly ADP-Ribose Polymerase) Inhibitors

Abstract Background: PARP inhibitors (PARPi) have demonstrated promising results in patients with advanced as well as early breast cancer carrying germline BRCA1/2 pathogenic variants (PV). Although there is increasing attention to the effect of BMI on the outcomes of cancer patients, there is limited data on its effect on BRCA-associated advanced breast cancer patients receiving PARPi therapy. In this report, we evaluate the effect of BMI on the outcomes of advanced breast cancer patients with a BRCA PV and who received PARPi therapy. Methods: Patients with BRCA 1/2 germline PVs who presented to the University of Texas MD Anderson Cancer Center Breast Medical Oncology clinics and were treated with PARPi between 2008-2022 as part of their treatment for metastatic or recurrent disease were included in the analysis. The patients were divided into four groups according to BMI level as follows: underweight (< 18.5 kg/m2), normal weight (18.5-24.9 kg/m2), overweight (25-29.9 kg/m2), and obese (≥30 kg/m2). Descriptive statistics, the Kaplan-Meier method, the Cox proportional hazards regression model, and Fisher’s exact test were used to report patient characteristics and outcomes. Progression-free survival (PFS) was calculated from the start of the PARPi therapy to the time of progression or death. Overall survival (OS) was calculated from the start of the PARPi therapy to the time of death of any cause. Results: One hundred and seven patients were treated with PARPi. The median BMI was 25.9 kg/m2 (14.8-61.2). In patients who received ≥2 cycles of PARPi, the overall response rate was 100% in the underweight group (n=4, 3.8%), 65.8% in the normal weight group (n=43, 41%), 64% in the overweight group (n=30, 28.6%), and 58.3% in the obese group (n=28, 26.7%). The median PFS was 5.4 months, 9.2 months, 9 months, and 8.6 months in underweight, normal weight, overweight, and obese patients, respectively. While the obese patients had a better outcome in terms of PFS (p = 0.0288), there was no significant difference observed in OS between BMI groups. Conclusion: In this analysis, we showed that obese patients with BRCA-associated advanced breast cancer had a better PFS. Future studies analyzing body composition parameters in BRCA-associated breast cancer patients treated with PARPi therapy could shed more light on the impact of obesity on outcomes. Citation Format: Fatma Akkoc Mustafayev, Mark Munsell, Rachel Layman, Clinton Yam, Angelica Gutierrez Barrera, Banu Arun. Clinical Implications of Body Mass Index (BMI) in BRCA-associated Advanced Breast Cancer Patients Treated With PARP (Poly ADP-Ribose Polymerase) Inhibitors [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-06-06.

Abstract PO1-05-01: Cyclin-dependent Kinase 4/6 Inhibitors Combined with Radiotherapy in the Management of Brain Metastases in HR-positive/HER2-negative Breast Cancer Patients

Abstract Purpose: Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) plus endocrine therapy demonstrated overall survival benefits in advanced breast cancer patients (ABC), hormone receptor-positive, HER2-negative (HR+/HER2-) and remains the mainstay in the first and second-line treatment. Brain metastases are rare at the beginning of treatment in this group of patients and are found more often during subsequent lines of treatment and other subtypes of breast cancer. However, there is a paucity of data on the safety and efficacy of multimodality CDK4/6i and radiotherapy treatment in the management of brain metastases. Thus, we performed a retrospective analysis of ABC patients (pts) treated at our institution with radiation therapy to the brain and CDK4/6i. Pts who received radiotherapy before CDK4/6i initiation or concurrently with CDK4/6i (group 1) were compared to the patients who progressed in the brain during CDK4/6i treatment and then received radiotherapy (group 2). The primary endpoint was progression-free survival (PFS) in group 1 vs. group 2; the secondary endpoints were local control (LC) within the brain in group 1 vs. group 2 and severe toxicity. Materials/Methods: Among 379 pts who received CDK4/6i, 26 pts (6.9%) received radiotherapy to the brain. 17 pts received radiotherapy before or concurrent with CDK4/6i and were included in group 1. Nine pts received radiotherapy after CDK4/6i discontinuation due to disease progression and comprised group 2. Results: The median age was 51.5 years (IQR range 41-62). Six pts had de novo metastatic disease. The majority of patients were treated in the first-line setting (15 pts, 58%). 17 pts received ribociclib, 7 palbociclib, and 2 abemaciclib. 15 pts received letrozole as an endocrine compound and 11 pts fulvestrant. 19 pts (73%) received previous chemotherapy. Six pts had an ECOG performance status of 0, 15 pts ECOG 1, and 5 pts ECOG 2. The most common local treatment was whole-brain radiotherapy with a total dose of 20 Gy delivered in 5 fractions (fr) (11 pts: 4 pts VMAT, 2 pts IMRT, 3 pts 3D, and 2 pts 2D). Eight pts received stereotactic radiation therapy (6 pts with Linac: 2 pts 24 Gy/2 fr, 2 pts 24 Gy/3 fr, 2 pts 25 Gy/5 fr; 1 pt GammKnife 20 Gy/1 fr, 1 pt Cyberknife 15 Gy/3 fr). Six- and 12-month PFS in group 1 was 88.2% (95% CI74.1-100) and 58.8% (95% CI: 37.7- 91.8), respectively, whereas in group 2, six- and 12-month PFS was 55.6% (95%CI: 31- 99.7) and 44.4% (95% CI: 21- 92.2), respectively. Six- and 12-month LC in group 1 was 92.3% (95%CI: 78.9-100) and 83.9% (65.7-100), respectively. LC in group 2 was poor: 3-month LC was only 66.7 (30-100). At a median follow-up of 8.8 months, no unanticipated toxicity was reported. Conclusion: Multimodality treatment with CDK4/6i and radiotherapy to the brain is safe and effective. Patients who developed metastases during CDK4/6i treatment tend to have a worse prognosis in comparison to those who received prior radiotherapy. CDK4/6i following radiotherapy seems to be an effective and valuable treatment option in this particular metastatic breast cancer population. Citation Format: Marcin Kubeczko, Dorota Gabryś, Anna Polakiewicz-Gilowska, Aleksandra Krzywon, Donata Gräupner, Barbara Łanoszka, Marta Mianowska-Malec, Aleksandra Leśniak, Katarzyna Świderska, Konstanty Chomik, Barbara Grandys, Michał Jarząb. Cyclin-dependent Kinase 4/6 Inhibitors Combined with Radiotherapy in the Management of Brain Metastases in HR-positive/HER2-negative Breast Cancer Patients [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-05-01.

Abstract PO5-05-13: Clinical utility of whole body low dose computed tomography for detecting bone metastasis in breast cancer patients: A cross sectional study

Abstract Clinical utility of Whole Body Low Dose CT scan for detecting bone metastasis in Breast cancer patients: A cross sectional study Background: Skeletal scintigraphy (Bone scan) is the imaging of choice to detect bone metastasis in locally advanced and metastatic breast cancer patients. Nuclear medicine facilities are however limited in their availability. As an alternative diagnostic modality to bone scan, we studied the diagnostic capability of Whole-Body Low Dose CT (WBLDCT) scan for detection of bone metastasis in these patients. Materials and Method: This cross-sectional study was conducted from November 2021 to May 2023 at a tertiary healthcare center in India with an aim to study the clinical applicability of whole-body low dose computed tomography scan for detecting bone metastasis in patients with breast cancer. Breast cancer patients with primary tumor measuring 5cm or more, pathologically proven axillary lymph node metastasis, Stage III/IV disease, symptoms attributable to metastasis and suspected disease recurrence were included. All patients underwent WBLDCT and Bone scan within a period of about 2 weeks. WBLDCT was done during the same time as conventional dose CT scan was being done as part of metastatic workup. WBLDCT acquisition protocol was set in CT scan machine by modulating the technical parameters like Care dose 4D-automated, Care kV semi, rotation time & noise index. The image analysis was performed by Radiologist and Nuclear medicine experts in a blinded fashion. Data was recorded in MS Excel sheet. Sensitivity, specificity, positive and negative predicative value, and concordance rates were calculated using SPSS software ver 25.0. Agreement amongst WBLDCT and Bone scan was calculated using Inter-rater agreement. p value < 0.05 was taken as significant. Results: 110 patients were enrolled in this study. The mean age of participants was 48.5 years and three fourth had stage III disease at presentation. Estrogen receptor positive disease was seen in 43.64% participants while 30% were triple negative. Her2neu positive disease was seen in 27.27% patients. Bone scan couldn’t be done in 03 patients who deferred treatment (these had no bone metastasis on WBLDCT). Both bone scan and WBLDCT detected bone metastasis in 19 patients. Bone scan picked up additional metastasis in three patients which were missed on WBLDCT. WBLDCT detected bone metastasis additionally in three patients which were not detected on Bone scan. Multiple lesions were most seen in vertebrae in 38.5% and 28.6% on bone scan and WBLDCT respectively. The sensitivity and specificity of WBLDCT for detection of bone metastasis was 86.36% and 96.47% respectively. The concordance rate between Bone scan and WBLDCT scan was 94.39% with an Inter-rater Kappa(k) quotient for agreement of 0.828 (p< 0.0001). Conclusion: WBLDCT scan has comparable diagnostic capability to skeletal scintigraphy in detecting bone metastasis in breast cancer and may be a useful alternative specially in resource limited settings. Table 1: Sensitivity, specificity, positive predictive value and negative predictive value of WBLDCT for detection of metastasis Variables Values Sensitivity (95% CI) 86.36% Specificity (95% CI) 96.47% AUC (95% CI) 0.91 Positive Predictive Value (95% CI) 86.36% Negative Predictive Value (95% CI) 96.47% Diagnostic accuracy 94.39% Inter-rater agreement (kappa) 0.828 Citation Format: Lipton Mitra, Suhani Suhani, Ankur Goyal, Rakesh Kumar, Mohit Joshi, Hemanga Bhattacharjee, Haresh KP, Raju Sharma, Rajinder Parshad. Clinical utility of whole body low dose computed tomography for detecting bone metastasis in breast cancer patients: A cross sectional study [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-05-13.

Abstract PO3-02-12: Dalpiciclib combination with letrozole as neoadjuvant therapy for HR-positive HER2-negative breast cancer: a single-arm, prospective exploratory clinical study

Abstract Background: CDK4/6 inhibitors effectively block tumor cells from progressing from the G1 phase to the S phase, thereby interrupting the cell cycle progression and inhibiting tumor cell proliferation. Dalpiciclib is a novel CDK4/6 inhibitor developed independently in China, which has been approved for use in combination with fulvestrant for the treatment of HR-positive/HER2-negative recurrent or metastatic breast cancer in patients who have experienced disease progression after prior endocrine therapy, or in combination with aromatase inhibitors as initial treatment for HR-positive/HER2-negative locally advanced or metastatic breast cancer patients. This study aims to explore the efficacy and safety of dalpiciclib in combination with letrozole as neoadjuvant therapy for HR-positive, HER2-negative breast cancer. Methods: This is a single-arm, open-label study that enrolled female breast cancer patients with early or locally advanced HR-positive, HER2-negative tumors and an ECOG performance status of 0 to 1. After enrollment, patients first received 4 cycles of dalpiciclib (150mg po qd, d1-21, q4w) in combination with letrozole as neoadjuvant therapy. Breast MRI was performed every 2 cycles, and treatment response was evaluated according to the RECIST 1.1 criteria. If patients achieved a confirmed complete response (CR) or partial response (PR) after 4 cycles, they would continue to receive an additional 4 cycles of dalpiciclib in combination with letrozole treatment. If the treatment response was stable disease (SD) or disease progression (PD), the investigator might modify other treatment regimens based on the individual circumstances of the subjects. The primary endpoint was residual cancer burden (RCB 0/I), and the secondary study endpoints were objective response rate (ORR), complete cell cycle arrest (CCCA, C1D15 Ki67≤2.7%) rate and safety. This study is registered at the Chinese Clinical Trial Registry Centre (registration No. ChiCTR2200057104). Results: From April 2022 to June 2023, a total of 38 patients were screened and enrolled in the study. All patients had ER ≥ 50%, and 84% (32/38) had Ki67 ≥ 88%. Among the 21 patients who completed the assessment after 4 cycles, the overall response rate (ORR) was 81% (17/21). Additionally, among the 22 patients who underwent C1D15 biopsy and Ki67 analysis, 55% (12/22) had C1D15 Ki67 ≤ 2.7%. After completing 8 cycles of neoadjuvant treatment with the combination of dalpiciclib and letrozole,12 patients underwent surgery. The postoperative RCB scores were as follows: 1 patient had RCB (0-I), and 11 patients had RCB (II-III). The most common adverse event was decreased neutrophil count (25/38 [66%]). Among the 38 patients, 16 (42%) experienced grade 3 or worse treatment-related adverse events. There were no occurrences of grade 4 or worse adverse events. Conclusions: The combination of dalpiciclib and letrozole has shown efficacy in downstaging and shrinking tumors in patients with early or locally advanced HR-positive/HER2-negative breast cancer. Patients who exhibit a positive response in the assessment after 4 cycles may consider it as a viable option for chemo-free neoadjuvant treatment. Citation Format: Jingruo Li, Yuanting Gu, Chuang Du, Jianhua Zhang, Yingying Zhang, Linfeng Zhang, Nan Wang, Lin Li, Fang Wang, Pengwei Lv, Hong Zong, Xinhong Pei, Bingjian Xue, Yan Wang, Dongcheng Gao. Dalpiciclib combination with letrozole as neoadjuvant therapy for HR-positive HER2-negative breast cancer: a single-arm, prospective exploratory clinical study [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-02-12.

Abstract PO5-21-10: Efficacy and Safety of Alpelisib in PIK3CA-mutated, hormone receptor-positive advanced breast cancer after a CDK4/6 inhibitor: An Open-label, Multi-centre, Prospective, Single Arm Clinical Trial

Abstract Introduction: Currently, patients with luminal metastatic breast cancer receive a CDK4/6 inhibitor in combination with endocrine therapy as a first or second line of treatment. When tumors become resistant to the CDK4/6 inhibitors, treatment with alpelisib (PI3K inhibitor) in combination with an endocrine agent can be a next treatment option if an activating PIK3CA mutation is confirmed (cfr. SOLAR-1 trial). However, limited data is available after treatment with CDK4/6 inhibitors (cfr. BYLieve trial) and even less about alpelisib in later lines of therapy. Therefore, we aim to investigate the therapeutic efficacy and safety of alpelisib in combination with an endocrine agent in PIK3CA-mutated advanced breast cancer patients in later lines after prior CDK4/6i treatment. Methods: This is an open-label, prospective, multi-centre, single arm clinical trial enrolling patients from both the University Hospital of Leuven (UHL) and Ghent University Hospital (GUH). For each patient, metastatic tumor was tested for PIK3CA mutations using the UHL 96 gene panel. Our endpoints are clinical benefit rate, progression-free survival, time to treatment discontinuation (defined as the date of starting alpelisib to the date of treatment discontinuation or death) and safety. Descriptive statistics were used. Results: Between June 18th 2019 and August 23rd 2021, 38 patients have been included with confirmed PIK3CA hotspot mutations. All patients had CDK4/6 inhibitor in an earlier treatment line. Median age at alpelisib initiation was 64 years (range: 39-82 years). Included patients had a median of four lines of systemic therapy for advanced disease prior to starting alpelisib (range: 1- 11). Clinical benefit rate (patients receiving ³ 6 months of treatment) was 26.3% (10/38). The median progression-free-survival as well as time to treatment discontinuation were 3 months (range: 1 – 18). Dose reduction due to toxicity occurred in 11 patients (29%), of which 7 due to hyperglycemia grade 3, 2 due to diarrhea grade 3, 1 due to rash grade 2 and 1 due to anorexia. Finally, 84% of patients (32/38) stopped alpelisib treatment because of progressive disease, 8% (3/38) because of intolerance, one patient died because of cerebral hemorrhage during treatment, one patient withdrew their informed consent and one patient is still ongoing with the treatment. Conclusion: Our trial demonstrates activity of alpelisib in patients with PIK3CA mutated advanced breast cancer in later lines of treatment after treatment with CDK4/6 inhibitors with a clinical benefit rate of 26.3%. Discontinuation of therapy due to toxicity was seen in only 8% of patients, although toxicity induced dose reduction was needed in 29% of patients. These findings support the results of the BYLieve trial and additionally show efficacy of alpelisib in later lines of treatment for hormone receptor-positive advanced breast cancer. Citation Format: Rik Van Severen, Anne-Sofie De Crem, Hava Izci, Laurence Slembrouck, Isabelle Vanden Bempt, Hans Wildiers, Kevin Punie, Eline Naert, Ingeborg Hilderson, Ann Smeets, Ines Nevelsteen, Anne Deblander, Nynke Willers, Patrick Berteloot, Ignace Vergote, Sileny Han, Adriaan Vanderstichele, Giuseppe Floris, Christine Desmedt, Hannelore Denys, Patrick Neven. Efficacy and Safety of Alpelisib in PIK3CA-mutated, hormone receptor-positive advanced breast cancer after a CDK4/6 inhibitor: An Open-label, Multi-centre, Prospective, Single Arm Clinical Trial [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-21-10.

Abstract PO2-11-08: Divorce and marital dissolution after Breast Cancer diagnosis in young breast cancer survivors in Mexico

Abstract Background: The current literature suggests that facing breast cancer can have significant effects on the relationship, for the better or for the worse. The needs of younger women with breast cancer are receiving increased attention, as 23.1% of all newly diagnosed invasive cancer occur in women age 50 or younger. Marital relationships, in particular, may be strained for younger cancer patients as they face health, emotional, and financial stressors from their cancer. The few studies that are available to date have examined the effect of breast cancer diagnosis on marital and relationship Purpose: We examined marital outcomes among young locally advanced breast cancer patients in our institution Methods: Eligible participants were women with diagnosis of breast cancer stage I–III, were at least 6 months post diagnosis, and age 50 or younger at the time of diagnosis. Demographic data collected. Participants reported their marital o relationship status at time of breast cancer diagnosis and after at least 6 moth post diagnosis, whether they were currently married or a member of an unmarried couple, divorced, widowed or separated Other variables examined regarding a possible separation, the reasons for separation, the influence of the cancer on the relationship, the positive or negative perception of the impact of cancer on the relationship, the highest educational attainment and employment status. Descriptive statistics, percentages, frequencies, mean values and standard deviations were calculated. Results: In total, 75 patients were eligible for inclusion with a total of 250 patient with diagnosis of locally advanced breast cancer. The median age was 44 (range 30–48). Most of the patients, stage I or II tumors (55%). The divorce or separation rate was 36%, higher than reported in the literature (14.5%). Among those who were separated, 77% reported that cancer contributed to the separation or divorce. Also, for those who stayed together, 81% reported an impact of the cancer on the relationship, of which 50% reported a negative impact. Of those who had separated, none were in a new relationship. Conclusions: The emotional burdens of cancer may lead to marital stress for younger cancer survivors.; support systems are needed to assist them in the years following diagnosis. Because the marital relationship has multiple dimensions, it is also important to explore and identify those areas of the couple's life that are affected by the experience Citation Format: Saúl Campos-Gomez, Andrea Ovando Trujillo. Divorce and marital dissolution after Breast Cancer diagnosis in young breast cancer survivors in Mexico [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-11-08.

Abstract PO1-06-05: Heterogeneity and prognostic characteristics of HER2-low breast cancer: A retrospective analysis of patients with HER2-negative metastatic breast cancer

Abstract Background: It remains uncertain as to whether low levels of HER2 positivity have any prognostic implications in breast cancer patients, whether HER2 levels can be inconsistent between primary tumors and metastatic lesions in individuals with advanced HER2-negative breast cancer, and how such inconsistencies may impact patient prognosis. Methods: A retrospective analysis of advanced breast cancer patients admitted to our hospital from from January 1st, 2010 to January 1st, 2019 was performed, with all patients that underwent at least one metastatic lesion biopsy being screened. The hormone receptor (HR) and HER2 profiles of both primary and metastatic lesions from these patients were confirmed, and HER2-positive patients (HER2 3+ immunohistochemistry [IHC] results or HER2 2+ IHC results with positive in situ hybridization [ISH] results) were excluded from further analyses. To examine the prevalence of HER2-low status across primary and metastatic cancers, the current study set out to detect inconsistencies between these two tumor compartments with respect to HER2-low status and to examine the prognostic implications of these findings in patients. Results: The median follow-up duration for this study at the cutoff date (December 31, 2021) was 49.3 (45.8-52.8) months. The current study examined 1,031 participants with HER2 and HR status data from both primary and metastatic tumors. The proportion of HER2-low expression was significantly higher in metastatic lesions than primary tumors (34.7% vs 25.7%), with a corresponding drop in the proportion of HER2-zero metastatic lesions (FIGURE 1). In a multivariate analysis, HER-2 upregulation was linked to HR status, which was established as an independent influencing factor, with such upregulation being most common in HR-positive individuals (P= 0.004). With respect to HER2 status of primary lesions, the medianl survival of patients in the HER2-zero was similar to HER2-low patients, regardless of HR status [44.8 months (95% CI 38.2-54.1) vs 41.5 months (95% CI 35.0-48.0)] (P = 0.954)(FIGURE 2A). However, when the HER2 status of metastatic lesions was examined, patients with HER2-low expression had a greater median OS than HER2-zero patients [47.6 months (95% CI 39.6-48.0) vs. 32.2 months (95% CI 24.6-40.0)] (P < 0.001)(FIGURE 2B). The median OS of patients that exhibited HER2 upregulation (zero→low) was longer than that of patients without such upregulation (zero-zero) (55.8 months (95% CI 45.0-66.6) vs. 32.4 months (95% CI 23.8-41.0)) (P < 0.001)(FIGURE 3A). Among HR-positive patients, HER2 upregulation was associated with significantly prolonged OS relative to patients without such upregulation [56.6 months (95% CI 44.6-68.6) vs. 41.7 months (95% CI 31.1-52.3)] (P=0.006)(FIGURE 3B), whereas survival outcomes were similar in these two groups in the HR-negative subgroup [44.8 months (95% CI 25.6-64.0) and 25.3 months (95% CI 20.4-30.3)] (P=0.103)(FIGURE 3C). However, independent of HR status, the median OS of patients who had HER2 downregulation (low→zero) was similar to those without downregulation (low→low)(FIGURE 3 D, E, F). Conclusion: These results support inconsistencies in HER2-low expression status between primary and metastatic lesions, with low HER2 levels in metastatic tumors being associated with improved survival outcomes. HR-positive patients are more likely to exhibit HER2 upregulation within metastatic lesions and experience corresponding prognostic benefits. Keywords: HER2-low, inconsistency, survival, prognosis, advanced breast cancer Citation Format: Huimin Lv, Min Yan, Mengwei Zhang, Limin Niu, Huiai Zeng, Huihui Sun, Shengnan Zhao, Jing Wang. Heterogeneity and prognostic characteristics of HER2-low breast cancer: A retrospective analysis of patients with HER2-negative metastatic breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO1-06-05.

Abstract PO3-05-10: Efficacy and safety of eribulin plus gemcitabine in second-line or beyond for patients with HER2-negative metastatic breast cancer (MBC): A multi-center, open-label, single-arm, phase II study

Abstract Background: Eribulin is a halichondrin non-taxane inhibitor of microtubule dynamics approved in China for advanced breast cancer patients who have received at least two prior chemotherapy treatments. The combination of eribulin and gemcitabine has demonstrated a similar progression-free survival (PFS) benefit as paclitaxel plus gemcitabine, with less neurotoxicity, for patients with MBC who have not received prior cytotoxic chemotherapy. However, the effect of eribulin plus gemcitabine on PFS in second line or beyond remains unclear. Methods: This open-label, single-arm, phase II study (NCT05263882) was conducted at 13 institutions in China. Eligible patients had histologically confirmed HER2-negative MBC and had received at least one prior taxane-containing chemotherapy regimen for advanced disease, and anthracycline-containing regimens in the adjuvant setting. Patients received intravenous infusions of eribulin (1.4 mg/m2) and gemcitabine (1.0 g/m2) on days 1 and 8 of a 21-day cycle. Efficacy outcomes, including PFS, objective response rate (ORR), and disease control rate (DCR), were assessed using RECIST v1.1. Adverse events (AEs) were graded according to NCI-CTC version 5.0. Results: A total of 65 patients were enrolled from November 2021 to May 2023; 47 (72.3%) had HR+/HER2- and 18 (27.7%) had triple-negative MBC. The median patient age was 50 years (range: 31-68), and the sites of metastasis were the bone (70.8%), liver (58.5%), lymph nodes (50.8%), lung (43.1%) and brain (10.8%). Patients had received a median of 3 prior lines of systemic treatment, 2 lines of chemotherapy, and 1 line of endocrine treatment. Among all patients, the ORR was 52.3%, the DCR was 92.3% and the median PFS was 7.6 months (Table). For the HR-positive subgroup, the median PFS was 8.4 months, while for the triple-negative subgroup, it was 7.6 months. Among patients who had received prior CDK4/6 inhibitor treatment, the median PFS was 7.2 months. In the subgroup of patients who had not received CDK4/6 inhibitor treatment, the median PFS had not been reached. The most common grade 3-4 AEs were hematological, including neutropenia (41.6%), leukopenia (33.9%), anemia (23.1%), and thrombocytopenia (15.4%). No grade ≥3 perceived AEs were reported. Conclusion: Eribulin plus gemcitabine was effective in heavily pretreated patients with HER2- MBC, while maintaining a predictable and manageable safety profile. Table. Summary of efficacy outcomes Citation Format: PeiJian Peng, Xiao-Lu Xu, Jin-Cai Zhong, Jin-Hui Ye, Zhi-Hui Wang, Hong Wang, Hong Lin, Cai-Wen Du, Guorong Zou, Jie Ouyang, Ying-Ying Shi, Fei Xu, Geng-Sheng Yu, Yong-Kui Lu, Yong-Xia Wang, Shi-En Cui, Lu-Zhen Li. Efficacy and safety of eribulin plus gemcitabine in second-line or beyond for patients with HER2-negative metastatic breast cancer (MBC): A multi-center, open-label, single-arm, phase II study [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-05-10.

Abstract PO2-15-09: Immune related cell fraction in peripheral blood and outcomes of advanced breast cancer patients treated with Eribulin

Abstract Background: Eribulin prolongs overall survival (OS) of patients with advanced breast cancer, and an ad-hoc analysis of the EMBRACE trial showed that baseline absolute lymphocyte count (ALC) was a predictor of OS prolongation. It has been suggested that eribulin improves the immune response to the tumor by improving the hypoxic environment through remodeling of local tumor vessels and reducing hypoxic stress, leading to OS prolongation. However, the details of the immune response mediated by eribulin remain to be fully elucidated. CD8+ cells attack cancer cells as cytotoxic T cells, while regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs) suppress activated T cells that attack cancer cells. In this study, we focused on CD8+ cytotoxic T cells, Tregs, MDSCs, and CD4-CD25-FoxP3+ cells in peripheral blood, analyzed the changes of those immune cells before and after eribulin treatment, and examined the effects on the outcomes of breast cancer patients. Methods: Nineteen patients with advanced or recurrent breast cancer treated with eribulin from April 2021 to May 2023 at our hospital were included. Peripheral blood was collected before drug administration as the first treatment (pre-treatment) and before drug administration in the second course (post-treatment), and the cell fractions, including CD4+ cells, CD8+ cells, CD4+CD25+FoxP3+ Tregs, CD11b+CD14+CD33+ MDSCs, and CD4-CD25-FoxP3+ cells, were analyzed by flow cytometry. The cutoff value for ALC was set at 1000 and NLR at 3.0, and each cell fraction was set to its respective median. Kaplan-Meier plots and logrank tests for progression-free survival (PFS) or OS were applied. Results: CD4+ cells were significantly lower post-treatment compared to pre-treatment (p=0.0140). Further, Tregs were significantly lower post-treatment compared to pre-treatment (p=0.0258). There were no significant changes in the levels of CD8+ cells, MDSCs, and CD4-CD25-FoxP3+ cells between pre- and post-treatment. We examined the association between each cell fraction and ALC or NLR, and found that CD4-CD25-FoxP3+ cells were significantly higher in cases with high NLR (p=0.0110). Analysis of the association between each cell fraction and prognosis at pre-treatment revealed that the high CD8+ cell group had significantly better PFS and OS than the low CD8+ cell group (p=0.0129 and p=0.0077, respectively). Interestingly, the high CD4-CD25-FoxP3+ cell group had significantly worse PFS than the low CD4-CD25-FoxP3+ cell group (p=0.0026). Conclusion: In the current study, Tregs in the peripheral blood of breast cancer patients significantly decreased after eribulin treatment, suggesting that eribulin may improve the immune microenvironment by suppressing immunosuppressive cells in cancer, including Tregs. In addition, the CD4-CD25-FoxP3+ cell fraction may serve as a biomarker for eribulin therapy, and further studies are needed to elucidate the details, including analysis of the constituent cells within the fraction. Citation Format: Masayuki Nagahashi, Ayako Bun, Mamiko Kuroiwa, Miki Komatsu, Sayaka Urano, Yukie Fujimoto, Aoi Oshiro, Ayumu Mitsuyoshi, Haruka Kanaoka, Akira Hattori, Reiko Fukui, Tomoko Higuchi, Arisa Nishimukai, Keiko Murase, Yuichi Takatsuka, Yasuo Miyoshi. Immune related cell fraction in peripheral blood and outcomes of advanced breast cancer patients treated with Eribulin [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-15-09.

Apriori prediction of chemotherapy response in locally advanced breast cancer patients using CT imaging and deep learning: transformer versus transfer learning.

Neoadjuvant chemotherapy (NAC) is a key element of treatment for locally advanced breast cancer (LABC). Predicting the response to NAC for patients with Locally Advanced Breast Cancer (LABC) before treatment initiation could be beneficial to optimize therapy, ensuring the administration of effective treatments. The objective of the work here was to develop a predictive model to predict tumor response to NAC for LABC using deep learning networks and computed tomography (CT). Several deep learning approaches were investigated including ViT transformer and VGG16, VGG19, ResNet-50, Res-Net-101, Res-Net-152, InceptionV3 and Xception transfer learning networks. These deep learning networks were applied on CT images to assess the response to NAC. Performance was evaluated based on balanced_accuracy, accuracy, sensitivity and specificity classification metrics. A ViT transformer was applied to utilize the attention mechanism in order to increase the weight of important part image which leads to better discrimination between classes. Amongst the 117 LABC patients studied, 82 (70%) had clinical-pathological response and 35 (30%) had no response to NAC. The ViT transformer obtained the best performance range (accuracy = 71 ± 3% to accuracy = 77 ± 4%, specificity = 86 ± 6% to specificity = 76 ± 3%, sensitivity = 56 ± 4% to sensitivity = 52 ± 4%, and balanced_accuracy=69 ± 3% to balanced_accuracy=69 ± 3%) depending on the split ratio of train-data and test-data. Xception network obtained the second best results (accuracy = 72 ± 4% to accuracy = 65 ± 4, specificity = 81 ± 6% to specificity = 73 ± 3%, sensitivity = 55 ± 4% to sensitivity = 52 ± 5%, and balanced_accuracy = 66 ± 5% to balanced_accuracy = 60 ± 4%). The worst results were obtained using VGG-16 transfer learning network. Deep learning networks in conjunction with CT imaging are able to predict the tumor response to NAC for patients with LABC prior to start. A ViT transformer could obtain the best performance, which demonstrated the importance of attention mechanism.

Abstract RF01-03: PARSIFAL-LONG: Extended follow-up of hormone receptor-positive/HER2-negative advanced breast cancer patients treated with fulvestrant and palbociclib vs. letrozole and palbociclib in the PARSIFAL study

Abstract Background: The Phase 2 PARSIFAL study assessed whether fulvestrant (FUL) or letrozole (LET) was the optimal endocrine partner for the cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) palbociclib (PAL) in patients (pts) with untreated, endocrine-sensitive, hormone receptor-positive (HR+)/HER2-negative (HER2-) advanced breast cancer (ABC) in the first-line setting. This trial failed to demonstrate an improvement in progression-free survival (PFS) of PAL+FUL over PAL+LET (Llombart-Cussac et al. Jama Oncol 2021). Following progression on CDK4/6i-based regimens in the metastatic setting, the EMERALD study (Bardia et al, SABCS 2022 GS3-01) identified early progressions (< 12 months [mo]) as a strong predictor of resistance to subsequent endocrine therapies. Here, we report updated PFS and overall survival (OS) from PARSIFAL, exploring a PFS <12 mo threshold as a prognostic factor for poor outcomes. Methods: This was an observational, international, multicenter study that included pts from the prospective PARSIFAL study, in which pts were randomly assigned (1:1) to receive PAL (oral 125 mg/day, 28-day cycles; 3 weeks on, 1 week off) plus FUL or LET at conventional doses. The primary objective was to extend the assessment of OS of PARSIFAL study with a longer median follow-up. Secondary objectives included extended PFS, other post-progression efficacy data, and the identification of new prognostic and predictive markers. The design had a planned recruitment of at least 388 pts with 195 deaths. The 2-sided stratified log-rank test (α = 0.05) had a 70% power to detect a hazard ratio ≤0.70 in favor of FUL + PAL arm. Results: A total of 389 pts (80.5%) from the PARSIFAL study were included in this analysis, involving 32 of the 47 original sites. Pts signed a new informed consent form according to local regulations. Demographic and baseline disease characteristics were similar between the PARSIFAL-LONG and the overall PARISFAL intention-to-treat populations. At the time of analysis, after a median follow up of 5.0 years (range, 0.1-7.3), 241 and 213 events were reported for PFS and OS, respectively. No differences in efficacy were observed between treatment arms whether for PFS (hazard ratio, 1.0, p=0.985) or OS (hazard ratio, 0.94, p=0.635). In accordance with the protocol for PARSIFAL-LONG, both arms were combined for subsequent analysis. The median PFS (mPFS) for the first-line PAL-based regimen population was 33.2 mo (95%CI, 27.7-39.5), with a median OS (mOS) of 65.4 mo (95%CI, 57.8-72.0). A total of 86 pts (22.1% of the population) had a mPFS time <12 mo (early progressors). mOS and mPFS for this early progressor subgroup were 24.0 mo (95%CI, 17.3-30.1) and 7.0 mo (95%CI, 5.6-8.3), respectively, and only 11 pts (12.8%) were still alive at the time of analysis. The remaining 303 pts (77.9%) were progression-free on PAL-based regimens at 12 mo (PFS≥12). The number of events for PFS and OS at this time were 165 (54.5%) and 138 (45.5%), respectively. mOS from randomization for the PFS≥12 subgroup was 81.5 mo (95%CI, 70.2-not achieved) and the mPFS was 49.8 mo (95%CI, 40.9-59.8). Following progression on PAL-based regimens, the PFS≥12 criteria was a strong predictor for mOS, with 27.0 vs 18.0 mo (hazard ratio, 0.67, 95%CI, 0.51-0.90, p=0.007) for PFS≥12 and early progressors, respectively. These differences may increase in the future, as 54.5% of pts with PFS≥12 are still alive compared to 12.8% of pts with an early progression. Conclusions: Extended follow-up analysis from PARSIFAL study confirms no major differences between LET or FUL when combined with PAL. mPFS and mOS results are consistent with those reported in other first-line trials involving different CDK4/6i. Progression within the first year of first-line CDK4/6i-based regimen for HR+/HER2- ABC pts may be prognostic of less favorable outcomes. Citation Format: Antonio Llombart-Cussac, José Manuel Pérez-García, Meritxell Bellet- Ezquerra, Florence Dalenc, Miguel Gil-Gil, Manuel Ruíz - Borrego, Joaquín Gavilá, Peter Schmid, Pilar Zamora, Duncan Wheatley, Eduardo Martínez-de Dueñas, Kepa Amillano, Antonio Antón, Paul Cottu, Gemma Viñas, Thierry Petit, Petra Tesarová, Juan Cueva, Marco Colleoni, Maria Purificación Martínez del Prado, Raquel Andrés, Marta Díaz Cabo, Susana Victorino, Miguel Sampayo-Cordero, Javier Cortés. PARSIFAL-LONG: Extended follow-up of hormone receptor-positive/HER2-negative advanced breast cancer patients treated with fulvestrant and palbociclib vs. letrozole and palbociclib in the PARSIFAL study [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr RF01-03.