HER2-negative Early-stage Breast Cancer Research Articles

Application of 21-gene recurrence risk score in patients with breast cancer

Objective: To investigate the relationship between 21-gene recurrence risk score (21-Gene RS) and the prognosis and clinicopathological features of hormone receptor (HR) positive, HER2-negative early breast cancer patients who did not receive neoadjuvant therapy. Methods: A total of 469 patients with HR positive and HER2-negative early breast cancer who received surgical treatment in the First Affiliated Hospital, Zhejiang University School of Medicine from January 2014 to October 2017 were selected. Their clinicopathological data were retrospectively analyzed. Tumor tissue samples were collected from patients, and the expression of 21-gene was detected by reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR). The 21-Gene RS was calculated according to the Trial Assigning Individualized Options for Treatment (TAILORx) RS grouping and National Surgical Adjuvant Breast and Bowel Project B-20 (NSABP B-20) RS grouping principles. Patients were divided into low (21-Gene RS<11 or 21-Gene RS<18), intermediate (11≤21-Gene RS<26 or 18≤21-Gene RS<31) and high (21-Gene RS≥26 or 21-Gene RS≥31) risk groups, and the clinicopathological features and prognostic differences of patients in different risk groups were compared. Statistical data were compared by chi-square test. Survival analysis was performed using Kaplan-Meier curve analysis and the differences between groups were compared using Log-rank test. Multivariate analysis was conducted by COX regression analysis. Results: Based on TAILORx RS grouping, the proportions of low-risk, intermediate-risk and high-risk groups among the 469 patients were 18.8% (88/469), 48.2% (226/469) and 33.0% (155/469), respectively. Based on NSABP B-20 RS grouping, the proportion of low-risk, intermediate-risk and high-risk groups were 43.1% (202/469), 37.5% (176/469) and 19.4% (91/469), respectively. The association of 21-Gene RS with histological grading, luminal typing, Ki-67 expression, and chemotherapy and treatment modalities were statistically significant (P<0.05) regardless of TAILORx RS grouping or NSABP B-20 RS grouping. Kaplan-Meier survival curve suggested poor prognosis in high-risk group (P<0.05, Log-rank test). Multivariate COX regression analysis showed that surgical method and 21-Gene RS were risk factors affecting the prognosis of patients. Conclusions: 21-Gene RS is significantly associated with the prognosis of patients with HR-positive, HER2-negative, early-stage breast cancer not receiving neoadjuvant therapy, as well as with their clinicopathological characteristics such as patients' histologic grade, luminal typing, Ki-67 expression, and whether or not they are treated with chemotherapy or other treatment modalities.The 21-Gene RS threshold of 11 and 26 or 18 and 31 can be used to grade the prognosis in Chinese patients with early-stage breast cancer. More researches are needed to guide the selection of postoperative adjuvant therapy for patients with HR-positive and HER2-negative early-stage breast cancer.

Factors that impact aromatase inhibitor adherence in early-stage hormone receptor positive breast cancer.

e12524 Background: Despite efficacy of aromatase inhibitors (AI) in improving survival for patients with hormone receptor positive (HR+) breast cancer, adherence to AI remains suboptimal. The aim of this study is to evaluate factors that may affect patient adherence to first-line AI. Methods: We retrospectively reviewed records of 195 female patients with HR+, HER2 negative early-stage breast cancer who were started on first-line adjuvant AI between 2011-2020 at our academic institution. We collected information on recurrence risk (defined by Oncotype score, with low risk ≤ 15, moderate risk 16-25, high risk ≥ 26), AI-related side effects, supportive therapy use for side effects, and socioeconomic demographics (i.e. income, insurance type, and race). We linked median family income with zip codes based on national census data and sorted them based on the Pew Research Center categorization. The primary end point was the rate of first-line AI adherence at 4 years. The Kruskal-Wallis rank sum test, Fisher’s exact test, and Pearson’s chi-squared test were used to compare AI adherence when varying patient profiles. Results: In our cohort, 50% (n=98) were adherent to first-line AI at 4 years, 9% (n=17) were still taking first-line AI but have not yet reached 4 years, and 41% (n=80) discontinued first-line AI early. Of those who discontinued first-line AI early, 68% (n=54) switched to an alternate endocrine treatment due to side effects, 4% (n=3) stopped all endocrine treatment, and 28% (n=23) were lost to follow up. AI-related side effects were common; 83% (n=162) reported AI-related side effects, yet only 27% of those patients received supportive therapy. Supportive therapy use was not significantly different when varying patients’ recurrence risk and socioeconomic demographics. In addition, adherence did not differ based on side effect frequency or supportive therapy use. The population’s Oncotypes included 36% (n=70) low risk, 36% (n=70) moderate risk and 12% (n=24) high risk; the remaining had no Oncotype sent. There was no significant difference in adherence among the risk groups. In evaluating demographics, the cohort’s median age was 62 and it included 9% Asian, 13% Black, 5% Hispanic, 54% White, and 19% Other/Unknown. The majority (62%) of patients were of middle income ($52,000-145,000), followed by 29% in upper and 9% in lower income. The minority (22%) of patients were on Medicaid. Those with a lower discontinuation rate were older (64 vs. 61, p=0.019), while there was no significant difference based on race, income, or insurance. Conclusions: Despite the small sample, it is reassuring that at our institution, long term adherence to first-line AI and supportive therapy use did not vary among socioeconomic demographics. However, a gap persists between the prevalence of AI-related side effects and usage of proven supportive treatments. Further study on strategies to enhance AI tolerance and adherence is needed.

Use of Oncotype vs. Breast Cancer Index (BCI) for extended endocrine therapy decisions: A single center analysis in stage IA hormone receptor positive breast cancer.

e13083 Background: Extended Endocrine Therapy (EET) for hormone receptor positive HER-2 negative early-stage breast cancer reduces late recurrence risks but raises concerns about toxicity. Biomarker tests like the Breast Cancer Index (BCI) are vital for identifying patients who could benefit from continued ET, reassuring others against unnecessary extension. This study evaluates prognostic implications for both Oncotype Dx (Recurrence score, RS) and BCI amidst concerns about added testing costs in patients with early stage, estrogen receptor (ER) positive breast cancer. Methods: This is a single institution retrospective review of Stage IA ER positive HER-2 negative breast cancer patients who underwent both Oncotype Dx and BCI testing from January 2021 to December 2023. Pearson's correlation coefficient (r) was used to assess the linear relationship between the assays (p&lt;0.05 for significance), analysis was performed with SAS software, version 9.4. Results: Fifty-eight patients with Stage IA ER positive HER-2 negative breast cancer who had both Oncotype and BCI results were identified (100% female; mean age 72.2 years [54-87]). After a median followed up of 72 months (63-75), no systemic or locoregional recurrences were reported. A low positive correlation between Oncotype and BCI was observed across the entire cohort (r=0.4058; p=0.0016). However, subgroup analysis showed no significant correlations: Oncotype &lt;11 (n=17; r=0.2415; p=0.3504), Oncotype ≤18 (n=43; r=0.0914; p=0.5600), Oncotype &lt;26 (n=51; r=0.2530; p=0.0733); Oncotype ≥26 (n=7; r=-0.5634; p=0.1878). Correlation was also not found in patients with Grade 1 tumor (n=16; r=0.3138; p=0.2365). Thirty-nine patients (67.24%) had their treatment recommendation changed based on BCI results. Side effects from ET affected 15 patients (25.86%) and included arthralgias (60%, n=9), hot flashes (26.67%, n=4), depression (13.33%, n=2), insomnia (6.67%, n=1), and others (53.3%, n=8). Twenty-two patients (37.93%) developed new osteopenia, and 6 (10.34%) new osteoporosis while on EET. Eight patients (13.79%) had ET interruption during their treatment course. Conclusions: Despite inclination towards cost-saving measures, Oncotype DX may be more useful to give prognosis in the early adjuvant period whereas BCI is more useful to evaluate late recurrence risk. Low or high Oncotype scores and tumor grade may not align with BCI findings. Considering the importance of managing toxicity against the risk of late recurrence, incorporating BCI testing can enhance EET recommendations, even for Stage I, node-negative, ER positive patients.

The immunomodulatory impacts of endocrine therapy on host immunity in early-stage hormone receptor positive, HER2 negative breast cancer.

572 Background: Endocrine therapy (ET) reduces mortality in hormonally driven breast cancer (BC). The impacts of ET on the estrogen receptor are well known; however, there is limited data on the impact of ET on the host's immune system. This project aims to elucidate the potential immunomodulatory effects of ET-induced estrogen deprivation in HR+/HER2 negative early-stage breast cancer patients (pts) as well as baseline differences between BC pts and healthy controls (HC). Methods: Pts with Stage I-III HR+/HER2- BC initiating ET after completion of local regional therapy and/or chemotherapy were enrolled (NCT03719495). Whole blood, E1 (estrone) and E2 (estradiol) levels were collected at baseline (T1), 4 weeks (T2), 12 weeks (T3) and 24 weeks (T4) after ET initiation. 5 cohorts were enrolled: premenopausal and postmenopausal HCs, premenopausal pts on tamoxifen (TAM) or aromatase inhibitors (AIs) plus ovarian suppression, postmenopausal pts on AIs. Bulk RNA sequencing of whole blood was performed using NuGEN mRNA-seq on the Illumina Nova-seq platform. Differential expression analysis was performed using DESeq2 between HC and ET groups at T1, and between T1 and T4 within BC pts. The Benjamini-Hochberg method was used to adjust the P values for multiple comparisons. A curated set of 192 immune related gene signatures was used in the gene signature analysis. For each signature/module, a score was computed by taking the median of the expression values from all genes in each gene signature. CIBERSORT analysis was performed using the LM22 signature gene file and 100 permutations. Paired t-test was performed to compare T1 and T4. Results: Between 2019 and 2023, 64 pts were enrolled. Pts with missing samples or prior chemotherapy were excluded in this analysis. T1 samples of 25 pts with BC versus 14 HCs revealed marked changes in circulating immune cell (IC) composition with 537 DEGs (p value &lt; 0.05). Circulating ICs in BC pts had marked upregulation of genes associated with oxidative phosphorylation, adipogenesis, interferon alpha, reactive oxygen species compared to HCs. Immune cell composition was inferred by CIBERSORT analysis which suggests that BC pts had fewer circulating naïve B cells (p=0.048) whereas regulatory T cells (p=0.025) and activated NK cells (p=0.0039) were higher in BC pts than HCs at T1. BC pts with reductions in E1/E2 levels 6 months after ET had 77 DEGs in PBMCs between T1 and T4. Gene signature analysis shows that B cells and NK cells (p=0.0077) signatures are elevated post ET whereas a reduction of neutrophil signature (p=0.0034) was noted. Conclusions: There are significant differences in the baseline IC repertoire/activity in BC pts compared to HCs. The reduction in B cell activity/number and an increase in regulatory T cell number suggests a possible compromised immune system in BC pts. After surgery and 6 months of ET, these suppressed immune phenotypes reversed. Clinical trial information: NCT03719495 .

Association of MammaPrint index and 3-year outcome of patients with HR+HER2- early-stage breast cancer treated with chemotherapy with or without anthracycline.

511 Background: The MammaPrint (MP) risk of distant recurrence signature identifies hormone receptor-positive (HR+), HER2-negative early-stage breast cancer (EBC) patients (pts) with increased or decreased chemosensitivity and chemotherapy (CT) benefit. The MINDACT trial demonstrated excellent outcomes for MP Low Risk tumors without CT, and previous studies show MP High Risk tumors exhibit higher sensitivity and benefit with CT. There remains an unmet clinical need for identifying biomarkers to inform specific regimen planning for pts who qualify for CT. Here, the association of MP index and 3-year (yr) Recurrence-Free Interval (RFI) was evaluated in pts with HR+HER2-, genomically High Risk Luminal B-Type EBC treated with taxane and cyclophosphamide (TC) vs anthracycline + TC (AC-T). Methods: The prospective, observational FLEX Study (NCT03053193) includes stage I-III breast cancer pts who received MP testing, with or without BluePrint (BP) molecular subtyping, and consented to full transcriptome and clinical data collection. Pts with HR+HER2- MP High Risk and BP Luminal B-Type tumors who received chemotherapy with 3-yr follow-up data (N = 614) were included. High Risk tumors were further classified into High 1 (H1; 0.000 to -0.569) or High 2 (H2; -0.570 to -1.000). Differences in 3-year RFI, defined as time from diagnosis to a local-regional recurrence, distant recurrence, or breast cancer specific death per STEEP 2.0 criteria, between H1 and H2 tumors were evaluated by Kaplan-Meier analysis and log-rank test, stratified by CT regimen. Results: Patients had similar age, menopausal status, race, and lymph node status between H2 vs H1 tumors. H2 tumors were more likely Grade 3, compared to H1 tumors. 86% of tumors were classified as H1 Luminal B-Type (N = 530) and 14% were classified as H2 Luminal B-Type (N = 84). AC-T treated tumors had non-significant differences in 3-yr RFI between H1 Luminal B-Type (95.3% [95% CI, 91.8-98.8]; N = 184) and H2 Luminal B-Type (97.7% [95% CI, 93.4-100.0]; N = 44). In contrast, pts with H2 Luminal B-Type (N = 40) tumors treated with TC demonstrated a significantly worse RFI of 86.4% (95% CI, 74.2-100.0) compared with 97.1% (95% CI, 95.1-99.2) in pts with H1 Luminal B-Type (N = 346) tumors, with an absolute difference of 10.7% (p = 0.0076). Conclusions: These data show that among pts with Luminal B-Type tumors, MP H2 have significantly worse 3-yr RFI than pts with MP H1 tumors when treated with TC. This further supports ongoing research demonstrating the significant benefits of anthracycline-based CT for treating H2 Luminal B-Type tumors. Conversely, MP H1 tumors do not appear to benefit from the addition of anthracycline to CT regimen. These FLEX data add to the growing evidence identifying MammaPrint as a comprehensive genomic signature regarding both prognosis as well as selection of systemic therapy for HR+HER2- EBC pts. Clinical trial information: NCT03053193 .

Abstract PO5-01-08: The impact of Human Epidermal growth factor Receptor 2 (HER2) expression by RT-PCR on tumor characteristics and outcome in estrogen receptor (ER) positive, HER2 negative early-stage breast cancer

Abstract Background: The role of HER2 expression in HER2 negative breast cancer is evolving. Whether HER2 expression has an impact on ER positive, HER2 negative early-stage breast cancer in unclear. Oncotype DX assay Recurrence Score comprises of standardized quantitative HER2 mRNA expression levels by RT-PCR. The objective of this study was to investigate the impact of Oncotype HER2 score on tumor characteristics and outcome. Methods: All women assigned to the Clalit Health Services registry between 2006 to 2011 with ER positive, HER2 negative early-stage breast cancer whose tumor were sent for oncotype were identified. Patients in which HER2 score was reported in the oncotype results were included. Differences in age, tumor characteristics and chemotherapy administration between lower HER2 score (H1), i.e. HER2 score ≤ 9.1, to higher HER2 score (H2), i.e. 9.2-10.7, were analyzed. 5-year Kaplan–Meier for distant recurrence free survival (DRFS) and overall survival (OS) were estimated and differences between H1 and H2 were evaluated. Analyses were repeated separately for node negative and for node positive (N mic and 1-3 lymph nodes) disease. Results: A total of 1535 patients were included, 948 patients with node negative disease and 587 with node positive disease. Of these, 814 and 721 patients were categorized to the H1 and H2 groups, respectively. Median follow-up was 5.4 years. The distribution of oncotype RS was different, with significantly lower proportion of patients with RS between 0-10 and higher proportion of RS above 25 in the H1 group compared to the H2 groups. This difference was identified both for patients with node negative and node positive disease (Table). The distributions of age, tumor size and histological subtype were comparable between the H1 and the H2 groups, both for node negative and node positive disease. Within each RS group, administration of chemotherapy was comparable between H1 and H2 groups, regardless of nodal involvement. DRFS and OS were not associated with HER2 score. For RS 0-25, node negative disease, 5-year DRFS was 96.2% in H1 and 96.4% in H2 groups (p=0.92) and 5-year OS was 97.2% in H1 and 98.1% in H2 groups (p=0.39). For RS &amp;gt;25, node negative disease, 5-years DRFS was 89% in H1 and 90.8% in H2 groups (p=0.33) and 5-year OS was 90.6% in H1 and 90.8% in H2 groups (p=0.7). Similarly, for node positive disease, DRFS and OS were comparable between H1 and H2 group in all subgroups. Conclusions: Low HER2 mRNA expression by Oncotype RT-PCR assay was associated with significantly high Oncotype RS. Patients' outcome was not directly affected by HER2 score and was determined by RS. Further study is desired to clarify the role of HER2 expression in early stage, luminal breast cancer. Table. Comparison of age and tumor characteristics between low (H1) and high (H2) HER2 score Citation Format: Hadar Goldvaser, Raz Mutai, Salomon Stemmer, Iryna Kuchuk, Margarita Tokar, Shani Paluch-Shimon, Rinat Yerushalmi, Karen Drumea, Ella Evron, Amir Sonnenblick, Einav Gal-Yam, Gil Bar Sela, Ayelet Shai, Rotem Merose, Avital Bareket-Samish, Lior Soussan-Gutman. The impact of Human Epidermal growth factor Receptor 2 (HER2) expression by RT-PCR on tumor characteristics and outcome in estrogen receptor (ER) positive, HER2 negative early-stage 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 PO5-01-08.

Abstract PO4-16-11: De-escalation of anthracyclines during adjuvant therapy based on Oncotype RS: A single institution experience in Mexico City

Abstract Introduction: In Mexico, hormone positive HER2 negative breast cancer is the most frequent subtype, accounting for 76.6% of cases. For patients undergoing local control management through surgery; adjuvant chemotherapy is usually followed depending on different risk factors. In order to avoid overtreatment, different genomic firms have been approved aiding in a more objective decision. One of these genomic firms is the Oncotype Recurrence score. The TAILORx and RxPONDER trials have provided guidance in determining which patients are candidates for chemotherapy depending on their menopausal status. However, it has not yet been determined whether patients requiring chemotherapy can receive an anthracycline-free regimen. In the Plan B clinical trial, a non-inferiority analysis was conducted on early-stage breast cancer patients who received anthracycline-based or non-anthracycline-based chemotherapy, with the non-anthracycline regimen being non-inferior, including patients with a RS &amp;gt; 25. We intend to reevaluate these findings in our Mexican population. Methods: We evaluated 217 patients with early stage hormone sensitive HER2 negative breast cancer who had an Oncotype Recurrence score (RS) result. This retrospective cohort study took place by analyzing electronic records from January 2011 to December 2017 with patients treated at the National Cancer Institute in Mexico City. We included patients 18 years of age or older, any sex with an Oncotype RS ≥ 16 in premenopausal patients or ≥ 26 in postmenopausal patients who received adjuvant chemotherapy with or without anthracyclines. Our primary endpoint was iDFS comparing TC vs AC-T. Overall survival was set as a secondary endpoint. Results: Of the 217 patients with an Oncotype recurrence score, only 46 patients received adjuvant chemotherapy of which 71.7% were premenopausal with a median age of 45 years. Stage II was the most common stage with 91.3% of the population, as well as ductal carcinoma with 82.6%. All patients had positive lymph nodes, 54.3% at least 1 lymph node. Most patients received AC-T adjuvant chemotherapy (60.9%), and only 39.1% received TC. Of the 46 patients analyzed, only 19.6% (9) had a recurrence upon follow-up (Table 1). Median time of follow up was 87.5 months. Difference in Disease free survival could not be established between patients receiving AC-T with 105 months (CI 95% 94.36-117.43 months) vs TC with 94.09 months (CI 95% 83.85-104.34 months, &amp;lt; p.918) (Figure 1). Overall survival did not have a statistical difference between both chemotherapy regimens, p&amp;lt; 0.649 (Figure 2A), when comparing Oncotype RS, overall survival was better in those with Oncotype OS &amp;lt; 26, p&amp;lt; 0.023 (Figure 2B). Discusion As described previously in the Plan B trial, TC was non inferior to the conventional adjuvant regimen of AC-T in Hormone positive HER2 negative early-stage breast cancer. Our results tend to show similar results when compared to the Plan B. An important aspect to our study was that 71.7% of our patients were premenopausal, where in the Plan B trial only 35% were premenopausal, considered a higher risk group of patients. Although a statical difference couldn´t be established due to our small sample size, in DFS or OS when comparing the chemotherapy regimen. Premenopausal patients with an Oncotype RS &amp;lt; 26 could receive an anthracycline free regimen, without impact in their overall survival. Larger prospective studies are necessary to assure this conclusion. Figure 1 DFS (TC vs AC-T) Figure 2 A and B Overall Survival Table 1 (Baseline characteristics) Citation Format: Carlos Arturo González Núñez, Paula Cabrera-Galeana, Juan Enrique Bargalló Rocha, Rafael Vazquez-Romo, Sergio Aguilar-Villanueva, Alexandra Garcilazo, Areli Velazquez-Martinez, Andrea Maliachi, Ruben Rodriguez, Esmeralda Romero-Bañuelos. De-escalation of anthracyclines during adjuvant therapy based on Oncotype RS: A single institution experience in Mexico City [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 PO4-16-11.

Abstract PO5-02-01: Concerning Discrepancies in Estradiol Levels in Premenopausal Women Receiving Abemaciclib and Ovarian Function Suppression

Abstract Background: Adjuvant abemaciclib in combination with endocrine therapy improves outcomes for patients with high-risk, hormone receptor-positive (HR+), HER2-negative early-stage breast cancer. In premenopausal women, the use of an aromatase inhibitor (AI) requires chemical or surgical ovarian function suppression (OFS). Our published case report of a premenopausal woman receiving adjuvant abemaciclib with elevated estradiol levels measured by the Abbott Alinity chemiluminescent microparticle immunoassay (CMIA) despite bilateral salpingo-oophorectomy (BSO) but low estradiol levels using liquid chromatography-mass spectrometry (LC-MS/MS) suggested an interference of abemaciclib with the immunoassay (PMID: 37124155). The aim of this study was to determine discrepancies in estradiol levels using CMIA compared to LC-MS/MS and subsequent treatment changes in a larger patient population. Methods: We conducted an IRB-approved retrospective review of premenopausal women with early-stage HR+ breast cancer treated with adjuvant OFS and abemaciclib at our institution from October 2021 to April 2023 who had at least 1 CMIA estradiol level drawn during abemaciclib therapy. Pathology, treatment plans, and lab data were abstracted from medical records. Postmenopausal estradiol levels were based on reference ranges of &amp;lt; 41 pg/mL using CMIA or &amp;lt; 15 pg/mL using LC-MS/MS. We utilized descriptive statistics to describe the population and management. Results: We identified 22 patients who met criteria for our review. The average age was 42.3 years, all had positive axillary nodes, 6 (27%) received neoadjuvant chemotherapy, and 15 (68%) received adjuvant chemotherapy. There were 14 (64%) patients who received leuprolide and 8 (36%) received goserelin, whereas 19 (86%) received AI and 3 (14%) received tamoxifen as their initial oral antiestrogen therapy. The majority of patients did not have baseline estradiol levels when starting OFS though after starting abemaciclib, 20 patients had CMIA estradiol levels in the premenopausal range, 9 of which had estradiol monitored by both CMIA and LC-MS/MS (Table 1). The average length of time from starting OFS to starting abemaciclib was 144.6 days with 1 patient switching from tamoxifen to OFS and AI after starting abemaciclib. Due to elevated CMIA estradiol, treatment changes included increased OFS dosage (5 patients), change of OFS (2 patients), and change to tamoxifen (3 patients). There were 6 patients who underwent BSO, 3 due to persistently elevated CMIA estradiol levels, 2 due to patient preference, and 1 due to a BRCA mutation. Following surgery, 2 patients had persistently elevated CMIA estradiol but low LC-MS/MS estradiol. The remainder of these patients did not have estradiol levels measured by CMIA. Conclusions: Our retrospective review demonstrated the likely interference of abemaciclib with the Abbott Alinity immunoassay as shown by 9 patients treated with OFS and abemaciclib with simultaneous premenopausal range CMIA estradiol levels and postmenopausal range LC-MS/MS estradiol levels. As up to 91% of patients in our study may have had a false positive estradiol level erroneously suggesting inadequate OFS, monitoring of estradiol levels using the CMIA assay in patients receiving adjuvant abemaciclib in addition to OFS could lead to changes in therapy that may be unnecessary. It is recommended that the LC-MS/MS assay be used when monitoring of estradiol levels is indicated in patients receiving abemaciclib concurrently with OFS. Table 1: Estradiol levels in patients receiving OFS and abemaciclib who had both CMIA and LC-MS/MS assays Citation Format: Alaina Kessler, Rima Patel, Emily Gallagher, Tianxiang Sheng, Damodara Rao Mendu, Amy Tiersten, Paula Klein, Aarti Bhardwaj, Anupama Goel, Joseph Sparano, Theresa Shao, Julie Fasano. Concerning Discrepancies in Estradiol Levels in Premenopausal Women Receiving Abemaciclib and Ovarian Function Suppression [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 PO5-02-01.

Abstract PO5-01-14: Genomic risk analyses in patients with clinical low risk ER-positive HER2-negative early breast cancer developing an early metastatic event

Abstract Background: Over the past decade, there have been notable changes in the definition of risk estimation in patients with early-stage breast cancer (EBC). Specifically, within the timeframe of 2000 to 2017, following Estrogen Receptor (ER) positive and HER2-negative EBC cases were classified as low risk according to the University Hospitals of Leuven (UHL) criteria of that time: if ER H-score was &amp;gt;200: all patients with tumors N0 and Grade (G) 1, ≤pT2; or G2-3 pT1a-b; in patients ≥40 years with tumors N0 and G2 pT1c-2 or G3 pT1c; in patients ≥ 55 years with tumors N0 G3 pT2 or N1 any Grade, pT≤2. For lower H-scores, other criteria applied. However, despite undergoing endocrine therapy, a subset of these patients with clinically low-risk tumors unexpectedly experienced metastasis within five years of initial diagnosis. This unforeseen outcome may indicate potential undertreatment, as these patients did not receive adjuvant chemotherapy. We have conducted a case-cohort study of those patients with early relapse and performed the current clinical risk assessment methods and genomic risk analyses. Methods: In this study, we included patients with ER-pos, HER2-neg early-stage breast cancer diagnosed between 1-1-2000 and 31-12-2017, who were classified as low-risk tumors by UHL guidelines at that time, who were older than 35 but younger than 71 years, had an unilateral, unifocal breast tumor with tumor size up to 5 cm. These patients did not receive adjuvant chemotherapy. We selected the patients that experienced early distant recurrence, defined as distant recurrence (DR) within 5 years after the initial diagnosis. To ensure comparability for the analyses they were matched to controls for grade, menopausal status, tumor size, lymphovascular invasion, progesterone receptor status, and the year of diagnosis. For each patient, we have calculated the clinical risk score according to the criteria outlined by Mymammaprint.com, based on the modified Adjuvant Online tool used in the MINDACT trial. For the analysis, formalin-fixed paraffin-embedded (FFPE) breast tumor tissue samples were subjected to in-house validated targeted RNA-based Mammaprint(MP) analysis by NGS (MP Agendia). Results: Of the 3190 patients with EBC at UHL during the study period, 2476 patients were considered for this analysis and fitted the clinical low-risk criteria defined low-risk at UHL. Among those, only 42 or 1.7% of the eligible cohort had developed metastasis within 5 years. Tissue for MP analysis was available for 35 of these cases and for their matched control. Due to technical failure, the 1:1 matching was lost and MP results were known for 28 cases and 27 controls. The patient and tumor characteristics of both groups were comparable. In this UHL clinical low-risk group, 21/28 (75%) cases would be identified as clinical high-risk by MyMammaprint.com and 18/27 (67%) controls. We identified 13 patients (46.43%) with high genomic risk within the group with DR and 9 (33.33%) within the control group. There was no statistically significant difference (p=0.412) in the proportion of genomically high-risk patients within the group with DR compared to the control group. Conclusions: In a database of patients with EBC of whom 98% did not develop metastasis within 5 years, we observed in a small series of chemotherapy naïve patients with early DR and UHL-defined clinical low-risk tumors, that nearly half had a genomically high risk of distant metastasis. Albeit numerically higher than the matched-control group, this observation was not significant and would warrant a larger sample size and power to confirm these results. Table. Genomic versus Clinical Risk by MyMammaprint.com Citation Format: Josephine Van Cauwenberge, Hava Izci, Hans Wildiers, Sileny Han, Christine Desmedt, Giuseppe Floris, Sara Vander Borght, Ann Smeets, Ines Nevelsteen, Isabelle Vanden Bempt, Patrick Neven. Genomic risk analyses in patients with clinical low risk ER-positive HER2-negative early breast cancer developing an early metastatic event [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 PO5-01-14.

Association of antibiotic exposure with residual cancer burden in HER2-negative early stage breast cancer

Antibiotic exposure during immunotherapy (IO) has been shown to negatively affect clinical outcomes in various cancer types. The aim of this study was to evaluate whether antibiotic exposure in patients with high-risk early-stage HER2-negative breast cancer (BC) undergoing treatment with neoadjuvant pembrolizumab impacted residual cancer burden (RCB) and pathologic complete response (pCR) in the pembrolizumab-4 arm of the ISPY-2 clinical trial. Patients received pembrolizumab for four cycles concurrently with weekly paclitaxel for 12 weeks, followed by four cycles of doxorubicin plus cyclophosphamide every 2 or 3 weeks. Patients who received at least one dose of systemic antibiotics concurrently at the time of immunotherapy (IO) were included in the antibiotic exposure group (ATB+). All other participants were included in the control group (ATB-). RCB index and PCR rates were compared between the ATB+ and ATB- groups using t-tests and Chi-squared tests, and linear and logistic regression models, respectively. Sixty-six patients were included in the analysis. 18/66 (27%) patients were in the ATB+ group. Antibiotic use during IO was associated with a higher mean RCB index (1.80 ± 1.43 versus 1.08 ± 1.41) and a lower pCR rate (27.8% versus 52.1%). The association between antibiotic use and the RCB index remained significant in multivariable linear regression analysis (RCB index-coefficient 0.86, 95% CI 0.20–1.53, P = 0.01). Our findings suggest that concurrent antibiotic exposure during neoadjuvant pembrolizumab in HER2-negative early-stage BC is associated with higher RCB. Further validation in larger cohorts is needed to confirm these findings.

MCM-2 Levels as a Potential Biomarker for Predicting High-Risk Breast Cancer Patients According to TAILORx Classification.

The minichromosome maintenance protein-2 (MCM-2) is a more sensitive proliferation marker than Ki-67. This study aimed to evaluate the relationship between MCM-2 and Oncotype DX recurrence score (ODX-RS) and determine an MCM-2 cutoff value in high-risk patients according to TAILORx risk categorization. Hormone receptor (HR) positive HER-2 negative early-stage breast cancer patients (pT1-2, pN0-N1, M0) who had ODX-RS were included in the study. According to the TAILORx trial, patients were divided into two groups with high (ODX-RS ≥26) and low risk (ODX-RS <26) in terms of ODX-RS. Formalin-fixed-paraffin-embedded tissues of patients were re-evaluated, and 3 µm sections were prepared for MCM-2 immuno-histochemical staining. The relationship between ODX-RS and the percentage of MCM-2 staining was evaluated in two groups. The ROC curve analysis was performed to determine the MCM-2 cut-off value for the TAILORx high-risk group (ODX-RS ≥26). The mean MCM-2 value was significantly higher in the high-risk group [(60.2 ± 11.2 vs 34.4 ± 13.8, p < 0.001)]. In the multivariate analysis, MCM-2 (OR: 1.27, 95% CI: 1.08-1.49, p = 0.003) and progesterone receptor (PR) levels ≤10% (OR: 60.9, 95% CI: 4.1-89.7, p = 0.003) were found to be independent factors indicating a high-risk group. A one-unit increase in MCM-2 level increased the likelihood of being in the high-risk group by 1.27 times. In the ROC curve analysis, the optimal MCM-2 cut-off level was 50 (AUC: 0.921, sensitivity: 86.7%, specificity: 96.0%, p < 0.001). Our study is the first study in the literature to investigate the relationship between ODX-RS and MCM-2 levels in HR-positive HER-2 negative early breast-cancer patients. In this study, MCM-2 was an independent risk factor in identifying high-risk patients according to TAILORx risk classification. MCM 2 cut-off value (50) may help the decision on adjuvant chemotherapy in patients where the Oncotype DX test cannot be performed.

Survival results according to Oncotype Dx recurrence score in patients with hormone receptor positive HER-2 negative early-stage breast cancer: first multicenter Oncotype Dx recurrence score survival data of Turkey.

The Oncotype Dx recurrence score (ODx-RS) guides the adjuvant chemotherapy decision-making process for patients with early-stage hormone receptor-positive, HER-2 receptor-negative breast cancer. This study aimed to evaluate survival and its correlation with ODx-RS in pT1-2, N0-N1mic patients treated with adjuvant therapy based on tumor board decisions. Estrogen-positive HER-2 negative early-stage breast cancer patients (pT1-2 N0, N1mic) with known ODx-RS, operated on between 2010 and 2014, were included in this study. The primary aim was to evaluate 5-year disease-free survival (DFS) rates according to ODX-RS. A total of 203 eligible patients were included in the study, with a median age of 48 (range 26-75) and median follow-up of 84 (range 23-138) months. ROC curve analysis for all patients revealed a recurrence cut-off age of 45 years, prompting evaluation by grouping patients as ≤45 years vs. >45 years. No significant difference in five-year DFS rates was observed between the endocrine-only (ET) and chemo-endocrine (CE) groups. However, among the ET group, DFS was higher in patients over 45 years compared to those aged ≤45 years. When stratifying by ODx-RS as 0-17 and ≥18, DFS was significantly higher in the former group within the ET group. However, such differences were not seen in the CE group. In the ET group, an ODx-RS ≥18 and menopausal status were identified as independent factors affecting survival, with only an ODx-RS ≥18 impacting DFS in patients aged ≤45 years. The ROC curve analysis for this subgroup found the ODx-RS cut-off to be 18. This first multicenter Oncotype Dx survival analysis in Turkey demonstrates the importance of Oncotype Dx recurrence score and age in determining treatment strategies for early-stage breast cancer patients. As a different aproach to the literature, our findings suggest that the addition of chemotherapy to endocrine therapy in young patients (≤45 years) with Oncotype Dx recurrence scores of ≥18 improves DFS.

State-of-the-art management of HER2-negative early breast cancer: Treatment patterns among healthcare professionals and concordance with expert recommendations.

553 Background: The management of high-risk HER2-negative early-stage breast cancer (EBC) has recently evolved with the addition of newer agents including abemaciclib, olaparib, and pembrolizumab as (neo)adjuvant therapy options for appropriate patients. To aid healthcare professionals (HCPs) in the recommended implementation of these agents, we developed an online treatment decision support tool providing case-specific treatment guidance from 5 breast cancer experts. Here, we report an analysis of cases entered into the tool by HCPs, comparing their planned treatment with expert recommendations. Methods: Expert therapy recommendations for 10 case scenarios in high-risk HER2-negative EBC based on 3 pivotal clinical trials (KEYNOTE-522, OlympiA, and monarchE) were obtained in March 2022. Patient and disease characteristics included hormone receptor (HR) status, BRCA mutational status, lymph node positivity, presence of residual disease after resection, and additional criteria based on the 3 practice-changing trials. HCPs entered specific patient and disease factors into the tool along with their intended treatment plan and were shown 5 individual expert treatment recommendations for the unique case scenario. Results: From June 2022 to January 2023, 547 HCPs entered 982 patient case scenarios into the tool. A comparison of treatment recommendations by experts and HCPs showed divergence for several case scenarios. For patients with high-risk HR-positive/HER2-negative EBC and no BRCA mutation, all 5 experts recommended adjuvant abemaciclib plus endocrine therapy. By contrast, 64% of HCPs’ therapy choices were discordant with the experts, with 49% choosing chemotherapy followed by endocrine therapy. For patients with triple-negative breast cancer (TNBC) who received neoadjuvant chemotherapy and have no residual disease, all 5 experts recommended observation, whereas 36% of HCPs recommended additional adjuvant therapy. In the setting of BRCA-mutated TNBC with residual disease after neoadjuvant pembrolizumab plus chemotherapy, 4 of 5 experts recommended adjuvant pembrolizumab plus olaparib, but just 33% of HCPs chose this combination. One third of HCPs who initially selected treatment options that diverged from expert recommendations or who were uncertain about treatment choice intend to change their therapy selection to align with the experts. Conclusions: Analysis of data from this tool suggests differences in clinical practice between experts and HCPs for multiple case scenarios of high-risk EBC, including examples of potential overtreatment. Moreover, our data demonstrate that this decision support tool may lead to better alignment of HCP treatment choices with experts, with the potential to improve clinical management of patients.

MAP3K1 expression is associated with progression and poor prognosis of hormone receptor-positive, HER2-negative early-stage breast cancer.

In this study, we assessed whether the overexpression of MAP3K1 promotes the proliferation, migration, and invasion of breast cancer cells, which affect the prognosis of hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative early stage breast cancer. Two HR-positive, HER2-negative breast cancer cell lines (MCF7 and T-47D) overexpressing MAP3K1 were transfected with two MAP3K1 short hairpin RNA plasmids (shMAP3K1 [#3] and shMAP3K1 [#5]). The proliferation, migration, and invasion of these cells were then examined. We assessed whether shMAP3K1 affects the cell cycle, levels of downstream signaling molecules (ERK, JNK, p38 MAPK, and NF-κB), and sensitivity to chemotherapeutic and hormonal agents. To assess the anti-tumor effect of MAP3K1 knockdown in the breast cancer orthotopic model, MCF7 and T-47D cells treated with or without shMAP3K1 (#3) and shMAP3K1 (#5) were inoculated into the mammary fat pads of mice. In total, 182 patients with HR-positive, HER2-negative T1 and T2 breast cancer and 0-3 nodal metastases were included. Additionally, 73 patients with T1 and T2 breast cancer and negative nodes who received adjuvant endocrine therapy alone were selected as an independent validation cohort. In both cell lines, shMAP3K1 (#3) and shMAP3K1 (#5) significantly reduced cell growth, migration, and invasion by downregulating MMP-9 and by blocking the G2/M phase of the cell cycle and its regulatory molecule cyclin B1. Moreover, both shMAP3K1 (#3) and shMAP3K1 (#5) downregulated ERK-, JNK-, p38 MAPK-, and NF-κB-dependent gene transcription and enhanced the sensitivity of both cell lines to doxorubicin, docetaxel, and tamoxifen. We observed that both shMAP3K1 (#3) and shMAP3K1 (#5) inhibited tumor growth compared with that in the scrambled group of MCF7 and T-47D cell orthotopic tumors. Patients with MAP3K1 overexpression exhibited significantly poorer 10-year disease-free survival (DFS) (70.4% vs. 88.6%, p = 0.003) and overall survival (OS) (81.9% vs. 96.3%, p = 0.001) than those without MAP3K1 overexpression. Furthermore, phospho-ERK (p < 0.001) and phospho-JNK (p < 0.001) expressions were significantly associated with MAP3K1 expression, and both phospho-ERK and phospho-JNK expressions were significantly correlated with poor 10-year DFS and OS. These biological findings, including a significant association between DFS and OS, and the expressions of MAP3K1, phospho-ERK, and phospho-JNK were further validated in an independent cohort. Multivariate analysis identified MAP3K1 expression as an independent poor prognostic factor for DFS and OS. Our results indicate that the overexpression of MAP3K1 plays a major role in the poor prognosis of HR-positive, HER2-negative early stage breast cancer.

Abstract P1-04-09: Correlating Predicted Adjuvant Therapy Benefit and Risk of Recurrence between Breast Cancer Index (BCI) and 21-gene Oncotype DX Recurrence Score (RS)

Abstract Background: The 21-gene Recurrence Score (Oncotype DX) is a genomic assay that provides prognostic information for distant recurrence risk and is predictive of adjuvant chemotherapy benefit in hormone receptor (HR)-positive, HER-2 negative early-stage breast cancer (EBC). The Breast Cancer Index (BCI) is another molecular gene expression-based assay that evaluates the utility of extending adjuvant endocrine therapy (ET) from 5 to 10 years and predicts risk of distant recurrence. In January 2021, the National Comprehensive Cancer Network (NCCN) Guidelines added BCI to guide duration of adjuvant ET as a category 2A recommendation. The goal of this study was to evaluate the association between BCI and RS in terms of their predicted benefit for adjuvant therapy and risk of distant recurrence. We also assessed the association of various anatomic and biologic tumor features with BCI. Methods: We performed a retrospective chart review of all patients with HR-positive EBC who had a BCI and Oncotype DX performed between 2007-2021. Demographics, tumor characteristics and BCI and RS results were extracted from the electronic medical record. Patients were categorized by BCI predictive of extended ET (formerly BCI high) versus not (formerly BCI low) and RS of low (0-10), intermediate (11-25) and high (26-100). Numerical values for distant recurrence risk were recorded for both BCI and Oncotype DX tests. Multivariable regression models were used to assess the relationship between BCI and Oncotype DX as well as factors associated with each. Results: We identified 153 women with HR-positive EBC with both RS and BCI performed. The median age of the population was 57 years and 25% were premenopausal. 32% (n=49) had a BCI result predictive of benefit from extended adjuvant ET. When comparing patients with BCI predictive of extended ET versus those with BCI not predictive of extended ET, there was no association between BCI and RS based on multivariate logistic regression models, p=0.7. A similar distribution of RS was observed between patients who had a BCI result predictive of benefit from extended ET versus not predictive. Among 49 patients with a BCI predictive of extended ET, 35% had high RS, 63% intermediate RS and 2% low RS. Among 104 patients with a BCI not predictive of extended ET, 24%, 73% and 3% had high, intermediate, and low RS, respectively. Multivariate regression models revealed an association between poorly differentiated tumors and BCI result predictive of extended ET, p=0.002. No associations were observed between BCI and menopausal status, ER%, PR%, tumor size or lymph node positivity. Regarding risk of recurrence, there was an association between BCI and Oncotype DX in terms of their predicted numerical risk of recurrence, p&amp;lt; 0.001. Higher percentage of PR positivity, poorly differentiated tumors, and lymph node positivity were associated with a higher risk of recurrence on the BCI. Conclusions: In our patient population selected to have Oncotype DX and BCI performed, we found no association between the two genomic assays in terms of their predictive benefit. However, there was an association between Oncotype DX and BCI in terms of their prognostic ability. Given the increased use of BCI since its inclusion in national guidelines, it is important to understand its relationship with other genomic assays especially when used to guide clinical decisions and estimate prognosis. Citation Format: Rima Patel, Nicole Casasanta, Zhiqiang Li, Melanie Kier, Julia Blanter, Sophie Sohval, Malin Hovstadius, Catherine Wu, Marc Fink, Xiang Zhou, Brittney Zimmerman, Krystal Cascetta, Rong Chen, William Oh, Amy Tiersten. Correlating Predicted Adjuvant Therapy Benefit and Risk of Recurrence between Breast Cancer Index (BCI) and 21-gene Oncotype DX Recurrence Score (RS) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-04-09.

Abstract P2-20-14: Relationship of HIF-1α and tumor infiltrating lymphocytes in patients with HER2-negative early-stage breast cancer treated with neoadjuvant chemotherapy

Abstract Title: Relationship of HIF-1α and tumor infiltrating lymphocytes in patients with HER2-negative early-stage breast cancer treated with neoadjuvant chemotherapy Authors: Grabinski VF, Oza HH, Gilkes DM, Shah MY, Cimino-Mathews A, Gabrielson E, Zhi I, Pipa Z, Lehman J, Ibanez HE, Ke S, Tsai HL, Stearns V, Santa-Maria CA Introduction: Hypoxia inducible factor 1α (HIF-1α) is an oxygen-dependent transcription factor expressed in areas of hypoxia associated with regulation of immune escape mechanisms, metabolism (CAIX), and results in cancer treatment resistance. High stromal tumor infiltrating lymphocytes (sTILs) are associated with pathologic complete response (pCR) to neoadjuvant chemotherapy (NACT) in breast cancer. We investigated associations between HIF-1α, sTILs and their relationship with pCR after NACT in patients with HER2-negative early-stage breast cancer. Methods: We identified patients with early-stage HER2-negative breast cancer at the Johns Hopkins Sidney Kimmel Comprehensive Cancer Center from 2000-2009 who received NACT, and had accessible breast tissue from biopsy and/or surgery. A pathologist scored nuclear HIF-1α (0, 1, 2, or 3), membranous CAIX (0, 1, 2, or 3), sTILs (0-100) from baseline (ie pre-NACT) and surgical tissue (if non-pCR). Statistical analysis considered the following variables: age, histology, race, menopausal status, tumor size, and node status. Chemotherapy regimens were divided into either anthracycline AND taxane versus anthracycline OR taxane. Wilcoxon rank-sum, Fisher exact, and Jonckheere trends tests were utilized to assess differences between groups. Results: 43 patients met the predefined criteria and were included in the analysis, 16% (n=7) obtained a pCR. Patient race, ethnicity, clinical tumor size, histology, clinical subtype (estrogen receptor positive (ER+) vs. triple negative (TN)), and NACT regimen were not associated with pCR. Older age (p=0.019), postmenopausal status (p=0.009), smaller surgical tumor size (p &amp;lt; 0.001), and surgical node-negative status (p &amp;lt; 0.001) were associated with pCR. Mean TILs score was 32.5% in patients achieving pCR versus 20% in those with non-pCR (p=0.46); mean HIF-1α was 2.42 in pCR group versus 2.57 in non-pCR (p=0.84). There was a trend of lower baseline sTILs with increasing nuclear HIF-1α score (p=0.085). Membranous CAIX was not associated with nuclear HIF-1α or baseline TILs, however, in the small proportion of patients (n=11) with CAIX scoring, higher membranous CAIX score at baseline (1 vs. 0) was associated with pCR (p=0.024). Conclusions: We observed that patients with pCR had a numerically higher sTILs level at baseline consistent with other studies, but did not find a correlation of HIF-1α and pCR. Patients with higher HIF-1α scores tended to have lower sTILS, suggesting that hypoxia may be leading to an immunosuppressive tumor microenvironment. Further characterizing the HIF-1α pathway and its effects on the immune microenvironment may help identify resistance mechanisms to chemotherapy and immunotherapy. Citation Format: Harsh Oza, Victoria Grabinski, Hector Ibanez, Ines Godet, Daniele Gilkes, Ashley Cimino-Mathews, Edward Gabrielson, Mirat Shah, W. Iris Zhi, Zoe Pipa, Jennifer Lehman, Suqi Ke, Hua-Ling Tsai, Vered Stearns, Cesar Augusto Santa-Maria. Relationship of HIF-1α and tumor infiltrating lymphocytes in patients with HER2-negative early-stage breast cancer treated with neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-20-14.

Abstract P3-05-59: ER+ HER2-negative mBRCA1/2 carriers breast cancer patients (n=81): Clinical outcomes and molecular characterization via the 21-gene Breast Recurrence Score (RS) test vs the general RS-tested population (799,986 samples)

Abstract Background: The RS assay is a validated prognosticator/predictor of chemotherapy (CT) benefit in ER+ HER2-negative early-stage breast cancer (BC). It is offered to pts irrespective of BRCA1/2 status. We compared RS results, single-gene expression and gene group scores, between pts with germline BRCA1/2 mutations and the general BC pt population undergoing RS testing. Treatments/outcomes in the mBRCA1/2 cohort were also examined. Methods: This real-life retrospective cohort study included consecutive ER+ HER2-negative mBRCA1/2 female carriers BC pts who had RS testing in 2004-2015. RS and gene expression data were compared to a previously described commercial use database (DB) (J Surg Oncol. 2020;122:611). Chi-square test and 1-sample t-test were used to compare RS distribution and single gene/gene group scores, respectively, between the cohort and the DB. Independent sample t-test was used to compare gene expression/gene group scores across pt subgroups within the mBRCA1/2 cohort. Fisher’s test/logistic regression were used to identify variables associated with distant recurrence in the mBRCA1/2 cohort. Results: The analysis included 81 pts in the mBRCA1/2 cohort and 799,986 BC samples in the DB. Age at diagnosis was younger in the mBRCA1/2 pts vs the DB (median [IQR], 56 [47-61.5] vs 60 [51-67] yrs; P&amp;lt;.001). In mBRCA1 and mBRCA2 pts (32 and 48 pts, respectively; for 1 pt, the BRCA gene involved was unknown), RS distribution shifted towards the high RS category when compared to the DB (Table). Comparing single-gene expression and gene group scores in mBRCA1 pts vs the DB, revealed statistically significant differences in 12 of the 16 cancer genes in the RS assay, and in 2 gene group scores, all in a direction contributing to higher RS results. Similar analysis with mBRCA2 pts, revealed significant differences in expression of 10 genes and 3 gene group scores, all in a direction contributing to higher RS results. The only statistically significant difference in gene expression between the mBRCA1 and mBRCA2 pts was in the ESR (higher in mBRCA2 pts; P=.0407) and MYBL2 gene (higher in mBRCA1 pts; P=.0365) (Table). Of the 32 mBRCA1 pts, 18 (56%) received CT (RS 0-25, 1/14 [7%]; RS 26-100, 17/18 [94%]; treatment information was unavailable for 1 pt). Of the 48 mBRCA2 pts, 19 (40%) received CT (RS 0-25, 5/27 [19%]; RS 26-100, 14/21 [67%]). With a median (IQR) follow up of 8.2 (5.6-9.7) yrs from diagnosis, 9 pts had distant recurrence (1 mBRCA1 pt, 8 mBRCA2 pts). Their median RS result was 25 (range, 16-41), and 4 received adjuvant CT. No statistically significant differences were observed between these 9 pts and the 72 non-recurring pts in terms of pt/disease characteristics and CT treatment. A trend towards significance was observed with respect to the BRCA gene involved (recurrence rate of 3.1% in mBRCA1 pts vs 16.7% in mBRCA2 pts, P=.078). A statistically significant association was found between the proliferation and invasion gene group scores and the odds of having distant recurrence (proliferation group score: odds ratio [OR], 23.60 [95% CI, 1.4-397], P=.0281; invasion group score: OR, 5.1 [95% CI, 1.1-23], P=.0339). The ER and HER2 gene groups scores were not associated with distant recurrence. Conclusions: Both mBRCA1 and mBRCA2 carriers are characterized by higher RS results that stem from a distinct gene expression profile of most genes in the RS assay. Single Gene Expression and Gene Group Scores vs the Commercial Use DB Citation Format: Rinat Yerushalmi, Adi Pomerantz, Ron Lewin, Shani Paluch-Shimon, Lior Soussan-Gutman, Frederick Baehner, Hillary Voet, Avital Bareket-Samish, Inbal Kedar, Yael Goldberg, Tamar Peretz-Yablonski, Luna Kadouri. ER+ HER2-negative mBRCA1/2 carriers breast cancer patients (n=81): Clinical outcomes and molecular characterization via the 21-gene Breast Recurrence Score (RS) test vs the general RS-tested population (799,986 samples) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-05-59.

Abstract P3-07-07: The use of ribociclib/letrozole combination as an alternative for neoadjuvant chemotherapy in selected patients with early luminal breast cancer

Abstract Introduction In hormone receptor-positive, HER2-negative early-stage breast cancer (BC), cyclin-dependent kinases 4 and 6 inhibition (CDK4/6i) in combination with endocrine therapy (ET) could represent an alternative to neoadjuvant chemotherapy (NAC). Methods NEOLBC is a randomized phase II trial that tailored neoadjuvant therapy in postmenopausal patients with early, luminal (ER &amp;gt;50%, PR any), HER2-negative, stage II/III BC based on the percentage of Ki67 positive cancer cells after a window of opportunity of two weeks letrozole. Patients with a Ki67 &amp;gt;= 1% after 2 weeks were randomized between ribociclib plus letrozole (RL) and chemotherapy (CT; AC-T regimen). The primary objective was to determine if RL gives a doubling in complete cell cycle arrest (CCCA; Ki67 &amp;lt; 1% on IHC) as compared to CT in the surgical specimen (70% vs. 35% of patients, respectively). Secondary endpoints included pathological response, toxicity and ER pathway activity (measured by the OncoSIGNal qPCR test). Results Out of 161 registered patients, 70 patients were randomized and 66 patients started treatment; 34 RL and 32 CT. Patient characteristics were equally distributed between the two groups, except for the PR status (RL 23.5% negative vs. 50.0% negative in the CT group). In the intention to treat analysis, the CCCA in the surgical specimen was similar for both groups: 35.3% in the RL vs. 31.3% in the CT group (p = 0.73). The pathological complete response (pCR) in the breast was not significantly different between the two groups (11.8% vs. 3.1%, p = 0.36) nor was the pCR rate in breast plus lymph nodes (8.8% vs. 3.1%, p = 0.61) for the RL vs. CT group, respectively. An explorative analysis on the difference in Ki67% (decline, no change, increase) from baseline to surgery showed a decline in 73.5% vs. 50.0%, no change in 17.6% vs. 31.3% and an increase in 8.8% vs. 18.8% of patients (p = 0.06) for the RL vs. CT group, respectively. In the RL group eight patients (23.5%) discontinued ribociclib early due to toxicity (two SAE’s were observed) vs. 10 patients (31.3%) discontinuing treatment in the CT group (one SAE was observed). Secondary endpoints, including the ER pathway activity analysis, will be presented in-depth during the meeting. Conclusion Although the primary endpoint was not met, the NEOLBC trial showed a similar CCCA and pathological response at surgery for RL vs. CT. Therefore, RL as an alternative for NAC merits further investigation in follow-up studies. ClinicalTrials.gov: NCT03283384 Citation Format: Anne Florine de Groot, Danielle Cohen, Joan B. Heijns, Caroline Mandigers, Diederick M. Keizer, Hein Putter, Elma Meershoek-Klein Kranenbarg, Marjolijn Duijm-de Carpentier, Kyra Dijkstra, Elise van Leeuwen-Stok, Gerrit-Jan Liefers, Sabine Linn, Judith Kroep. The use of ribociclib/letrozole combination as an alternative for neoadjuvant chemotherapy in selected patients with early luminal breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-07-07.

152P Molecular characterization by the 21-gene breast cancer (BC) Recurrence Score (RS) test of BRCA1/2 mutation carriers (mBRCA1/2) versus the general BC patient (pt) population

The RS assay is a validated test used to guide treatment decisions in ER+ HER2-negative early-stage BC. We compared RS distribution and expression of the single genes/gene groups within this assay between mBRCA1/2 carriers ER+ HER2-negative BC pts vs the general BC pt population undergoing RS testing.

Prognostic significance of different molecular typing methods and immune status based on RNA sequencing in HR-positive and HER2-negative early-stage breast cancer

BackgroundThis study was conducted to evaluate the prognostic significance of different molecular typing methods and immune status based on RNA sequencing (RNA-seq) in hormone receptor (HR)-positive and human epidermal growth factor receptor 2 (HER2)-negative (HR + /HER2-) early-stage breast cancer and develop a modified immunohistochemistry (IHC)-based surrogate for intrinsic subtype analysis.MethodsThe gene expression profiles of samples from 87 HR + /HER2- early-stage breast cancer patients were evaluated using the RNA-seq of Oncotype Dx recurrence score (RS), PAM50 risk of recurrence (ROR), and immune score. Intrinsic tumor subtypes were determined using both PAM50- and IHC-based detection of estrogen receptor, progesterone receptor, Ki-67, epidermal growth factor receptor, and cytokeratins 14 and 5/6. Prognostic variables were analyzed through Cox regression analysis of disease-free survival (DFS) and distant metastasis-free survival (DMFS).ResultsSurvival analysis showed that ROR better predicted recurrence and distant metastasis compared to RS (for DFS: ROR, P = 0.000; RS, P = 0.027; for DMFS, ROR, P = 0.047; RS, P = 0.621). Patients with HR + /HER2- early-stage breast cancer was classified into the luminal A, luminal B, HER2-enriched, and basal-like subtypes by PAM50. Basal-like subgroups showed the shortest DFS and DMFS. A modified IHC-based surrogate for intrinsic subtype analysis improved the concordance with PAM50 from 66.7% to 73.6%, particularly for basal-like subtype identification. High level of TILs and high expression of immune genes predicted poor prognosis. Multi-factor Cox analysis showed that IHC-based basal-like markers were the only independent factors affecting DMFS.ConclusionsPrognosis is better evaluated by PAM50 ROR in early-stage HR + /HER2- breast cancer and significantly differs among intrinsic subtypes. The modified IHC-based subtype can improve the basal-like subtype identification of PAM50. High immunity status and IHC-based basal-like markers are negative prognostic factors.