Recurrent Metastatic Breast Cancer Research Articles

Clinicopathogenomic analysis of PI3K/AKT/PTEN-altered luminal metastatic breast cancer in Japan.

This rapid communication highlights the correlation between protein kinase B alpha (AKT1)-phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA)- phosphatase and tensin homolog (PTEN) alterations and clinicopathological factors in Japanese patients with metastatic recurrent breast cancer (mBC). This study analyzed 1967 patients with luminal-type breast cancer who underwent cancer gene panel testing. The results demonstrated that AKT pathway alterations, including PI3K/AKT/PTEN, occurred in 1038 (52.8%)cases. Patients with AKT pathway mutations were older (p = 0.002) and had a higher rate of invasive lobular carcinoma (ILC) histology (p = 0.001), progesterone receptor (PgR) positivity (p = 0.006), and bone metastases (p = 0.001), and a lower rate of germline BRCA2 (p < 0.001). Comprehensive genomic profile results demonstrated a higher tumor mutational burden (TMB) (< 0.001) and lower tumor BRCA1/2 expression (< 0.001) in patients with mutations in the AKT pathway. These results are crucial for characterizing candidates for AKT pathway-targeted molecular therapies and conceptualizing optimal treatment strategies. Clinical trial registration: This study is an observational study and is therefore not registered with the clinical trials registration.

Abstract A048: The Loss of Cholesterol Efflux Pump ABCA1 Skews Macrophages Towards a Pro-tumor Phenotype and Facilitates Breast Cancer Progression

Abstract Breast cancer is the most common and second-leading cause of cancer-related fatalities in women in the United States. The primary cause of mortality is often the recurrence of metastatic breast cancer. While immunotherapy shows some effectiveness, it has only been approved for patients who stain positive for PD-L1. Previous research in our lab has shown that macrophage function can be regulated through disruption in cholesterol metabolism. Additionally, elevated plasma cholesterol levels have been associated with breast cancer recurrence. These findings underscore the impact of cholesterol homeostasis in tumor-associated macrophages on breast cancer progression. An in-depth computational screen helped us pinpoint ABCA1—a cholesterol efflux protein whose elevated mRNA expression linked to increased survival. In addition to efflux, ABCA1 can also translocate cholesterol from the inner leaflet of the plasma membrane to the outer layer. Highlighting the clinical importance of ABCA1 are our findings that show that increased ABCA1 levels within breast tumors correlate to an increase in cytotoxic T Cells, and T cell effector enzymes (Prf-1 and Gzmb), and improved survival rates. Importantly, our in vitro studies suggest that ABCA1 influences several functions of macrophages relevant to tumor biology. Specifically, ABCA1 shifts macrophages towards an anti-cancer phenotype by (1) increasing their ability to infiltrate tumor spheroids, (2) decreasing angiogenesis, (3) decreasing efferocytosis—an immune-suppressive phagocytic process devoid of antigen presentation, and (4) enhancing the expansion, migration, and activity of cytotoxic T cells. The culmination of these attributes were demonstrated by our observations that syngeneic grafts of E0771 mammary tumors grew at an accelerated rate in mice with a myeloid-specific knockout of ABCA1 (ABCA1fl/fl;LysMcre+) compared to control mice. ABCA1 transports cholesterol from macrophages to a lipid-poor ApoA1 protein and facilitates the formation of nascent HDL via the reverse cholesterol transport pathway. We leveraged this mechanism to therapeutically target ABCA1 using ApoA1 mimetics 5A and 4F. Our data so far indicates that ApoA1 mimetics phenocopy ABCA1 overexpression skewing macrophages towards an anti-tumor phenotype. Importantly, treatment with 5A in mice grafted with 4T1 metastatic breast cancer cell line resulted in marked reduction in tumor burden. Additionally, we observed an increased infiltration of cytotoxic T cells and a decrease in CD31 expression, suggesting reduced blood vessel formation. Collectively, our data strongly supports the role of ABCA1 in the development of breast cancer. The expected results from this research will lay the groundwork for future therapeutic strategies for the use of ABCA1 and ApoA1 mimetics in the treatment of breast cancer. Citation Format: Shruti Bendre, Natalia Krawczynska, Shaunak Bhogale, Erin Weisser, Simon Han, Basel Hajyousif, Avni Singh, Rajendra KC, Yu Wang, Claire P Schane, Adam T Nelczyk, Dhanya Pradeep, Lara Kockaya, Hashni Epa Vidana Gamage, Kevin VanBortle, Emad Tajkorshid, Saurabh Sinha, Wendy A Woodward, Wonhwa Cho, Erik R Nelson. The Loss of Cholesterol Efflux Pump ABCA1 Skews Macrophages Towards a Pro-tumor Phenotype and Facilitates Breast Cancer Progression [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2024 Oct 18-21; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2024;12(10 Suppl):Abstract nr A048.

Characterizing cancer-related cognitive impairments and impact on quality of life in women with metastatic breast cancer.

Little is known about cancer-related cognitive impairments (CRCI) in women with metastatic breast cancer (MBC). The purpose of this study is to (1) comprehensively describe CRCI and any associated psychosocial and behavioral symptoms, (2) determine observable sociodemographic and clinical risk factors for CRCI, and (3) explore cognitive and psychosocial predictors of quality of lifeand social functioning in women living with MBC. Using a cross-sectional design, women with MBC completed assessments (objective and subjective measures of CRCI including 3 open-ended questions, measures of psychosocial and behavioral factors, and assessments of quality of life and social function), and data were analyzed using descriptive statistics, qualitative content analysis, correlation analyses, t tests, analysis of variance, and linear regression models. Data from 52 women were analyzed. 69.2% of the sample reported clinically significant CRCI and 46% of the sample scored < 1 standard deviation below the standardized mean on one or more cognitive tests. Those with triple-negative MBC (compared to HER2+), recurrent MBC (compared to de novo), and no history of chemotherapy had worse subjective CRCI, and those without history of surgery and older age had worse objective CRCI. Subjective CRCI, but not objective CRCI, was significantly associated with quality of life and social functioning. Subjective and objective CRCI are likely a common problem for those with MBC. Subjective CRCI is associated with poorer quality of life and lower social functioning. Healthcare providers should acknowledge cognitive symptoms, continually assess cognitive function, and address associated unmet needs across the MBC trajectory.

Results from the randomized KEYNOTE-355 study of pembrolizumab plus chemotherapy for Asian patients with advanced TNBC

In the phase 3 KEYNOTE-355 study (NCT02819518), pembrolizumab plus chemotherapy demonstrated statistically significant and clinically meaningful improvements in progression-free survival (PFS) and overall survival (OS) versus placebo plus chemotherapy among patients with previously untreated locally recurrent inoperable or metastatic triple-negative breast cancer (TNBC) and programmed cell death ligand 1 (PD-L1) combined positive score (CPS) ≥ 10 tumors. We analyzed outcomes for the subgroup of patients enrolled in Asia in KEYNOTE-355. Patients received pembrolizumab 200 mg or placebo (2:1 randomization) every 3 weeks for 35 cycles plus investigator’s choice chemotherapy. Primary endpoints were PFS per Response Evaluation Criteria in Solid Tumors version 1.1 and OS. Among patients enrolled in Hong Kong, Japan, Korea, Malaysia and Taiwan (pembrolizumab plus chemotherapy, n = 113; placebo plus chemotherapy, n = 47), 117 (73.1%) had PD-L1 CPS ≥ 1 and 56 (35.0%) had PD-L1 CPS ≥ 10. Median time from randomization to data cutoff (June 15, 2021) was 43.8 (range, 36.8‒53.2) months (intent-to-treat [ITT] population). Hazard ratios (HRs [95% CI]) for PFS in the CPS ≥ 10, CPS ≥ 1, and ITT populations were 0.48 (0.24‒0.98), 0.58 (0.37‒0.91), and 0.66 (0.44‒0.99), respectively. Corresponding HRs (95% CI) for OS were 0.54 (0.28‒1.04), 0.62 (0.40‒0.97), and 0.57 (0.39‒0.84). Grade 3/4 treatment-related adverse events (AEs) occurred in 77.9% versus 78.7% of patients with pembrolizumab plus chemotherapy versus placebo plus chemotherapy. No grade 5 AEs occurred. Clinically meaningful improvement in PFS and OS with manageable toxicity were observed with pembrolizumab plus chemotherapy versus placebo plus chemotherapy in patients enrolled in Asia with previously untreated, inoperable or metastatic TNBC.Trial registration: ClinicalTrials.gov, NCT02819518.

The Effect of C-Reactive Protein/Lymphocyte Ratio (CLR) on PFS in Metastatic Breast Cancer Patients Treated with CDK4/6 Inhibitors: A Novel Biomarker.

Hormone positive breast cancer is a tumor with high mortality. Combining antihormonal therapy with cyclin dependent kinase 4/6 inhibitors (CDK4/6i) has resulted in longer survival. The effect of inflammatory parameters such as c-reactive protein and c-reactive protein/lymphocyte ratio (CLR) on efficacy and survival in CDK4/6i treatment is unknown. In our study, we aimed to investigate the role of CLR and some parameters in predicting progression-free survival (PFS) with CDK4/6i. This retrospective cohort study included 78 patients with denovo and recurrent metastatic breast cancer treated with CDK4/6i. Cut off values for the prediction of mortality by various numerical parameter scores were performed by ROC Curve analysis. The effect of clinical variables, inflammatory and histopathological parameters on survival was analyzed by Kaplan-Meier method. Neutrophil/lymphocyte ratio (NLR) and CLR were statistically significant in predicting mortality (p < 0.05). Ki67 and CLR were correlated with PFS. Age and CLR were correlated with OS (p < 0.05). CLR was statistically significant for both PFS (p = 0.022) and OS (p = 0.006). In patients with metastatic hormone-positive breast cancer using CDK4/6i, low CLR and low Ki67 were correlated with longer PFS duration.

De novo versus recurrent metastatic breast cancer affects the extent of brain metastases.

We aimed to identify factors associated with the extent of brain metastases in patients with breast cancer to help distinguish brain oligometastases (1-4 brain metastases) from extensive metastases (5 or more brain metastases). This retrospective observational study included 100 female patients diagnosed with brain metastases from breast cancer at a single institution between January 2011 and April 2022. Patient demographics and tumor characteristics were compared between the brain oligometastases group and the extensive metastases group. Multivariable logistic regression analysis was performed to determine the independent factors, including age at initial diagnosis, initial stage, breast cancer subtype, detection time of brain metastases, and de novo or recurrent status of the metastatic disease. In a subgroup analysis of patients with brain oligometastases, demographic and tumor characteristics were compared between patients with single and two-four brain metastases. Of the 100 patients, 56 had brain oligometastases, while 44 had extensive brain metastases. The multivariable logistic regression analysis revealed that only the de novo/recurrent status of metastatic breast cancer was significantly associated with the extent of brain metastasis (p = 0.023). In the subgroup analysis of 56 patients with brain oligometastases, those diagnosed at an earlier stage were more likely to have a single brain metastasis (p = 0.008). Patients with de novo metastatic breast cancer are more likely to develop extensive brain metastases than those with recurrent metastatic breast cancer. This insight could influence the development of tailored approaches for monitoring and treating brain metastases, supporting the potential advantages of routine brain screening for patients newly diagnosed with stage IV breast cancer.

Abstract PO5-05-14: Survival in Young Women with De Novo or Recurrent Metastatic Breast Cancer

Abstract Background. Approximately 12,000 women aged 40 years or younger are diagnosed with breast cancer every year in the United States alone. Limited data exist regarding survival in young women with metastatic breast cancer (MBC), particularly when considering modern tumor subtyping and treatment, though previous studies have suggested that patients presenting with MBC at diagnosis (de novo stage IV) have better prognosis than those who develop recurrent MBC after initial diagnosis of stage 0-III disease. We sought to determine survival rates in young patients with MBC stratified by disease presentation (de novo versus recurrent) and subtype. Methods. The Young Women’s Breast Cancer Study (YWS) is a multicenter, prospective cohort which enrolled 1,302 women diagnosed with stage 0-IV breast cancer at age ≤40 from 13 North American academic and community-based sites from 2006-2016. The current median follow-up is 10.1 (range 0.4-16.3) years. Histopathology slides were centrally reviewed for 97% of the participants, and clinical tumor molecular subtypes have been detailed. In the recurrent group, receptors were obtained from the initial breast surgery. Descriptive analyses were used to characterize patients with de novo or recurrent MBC, including demographic and disease characteristics, and survival rates. Overall survival was estimated using the Kaplan-Meier method and compared by log-rank test between those who presented with de novo and relapsed disease overall and within tumor subtypes. Results. Among 246 patients included in this analysis, 74.0% (n=182) had recurrent MBC and 26.0% (n=64) had de novo MBC. Most patients were white (n=208, 84.6%), while 6.9% were Asian (n=17), 4.5% Black (n=11), 0.8% Native American (n=2), 0.8% multiracial (n=2) and 2.4% other/unknown (n=6). A total of 4.5% of patients were Hispanic (n=11). Median age at diagnosis of de novo MBC was 37 years and 40 years for diagnosis of metastasis in the recurrent group. Median disease-free interval was 3.23 (range 0.32 – 13.84) years for the recurrent MBC group. Among all patients with MBC, most (55.7%, n=137) had estrogen receptor (ER) and/or progesterone receptor (PR)-positive, human epidermal growth factor receptor 2 (HER2)-negative disease, whereas 17.9% (n=44) had ER and/or PR-positive HER2-positive, 7.3% (n=18) had ER/PR-negative HER2-positive, and 18.7% (n=46) had triple-negative tumors. A greater proportion of participants (43.8%, n=28) had HER2-positive disease in the de novo group than in the recurrent group (18.7%, n=34), P=&amp;lt; 0.0001. A total of 10.9% (n=7) of de novo patients had a germline BRCA mutation, compared to 13.7% (n=25) in the recurrent group. Median survival was 5.09 (95% CI: 3.74 – 6.38) years in the de novo group and 2.63 (95% CI: 1.98 – 3.21) years in the recurrent MBC group (P=0.0004). When stratifying by subtype, survival among patients with de novo ER and/or PR-positive HER2-positive disease was longer than among patients with recurrent disease (P=0.0149), whereas there were no statistically significant differences in survival between the de novo and recurrent disease groups in other disease subtypes (Table 1). Conclusion. Survival in young women with MBC is highly heterogeneous and varies substantially by tumor subtype and disease presentation. Those with de novo ER and/or PR-positive HER2-positive subtype appear to have better outcomes than those with recurrent MBC with the same subtype. These findings can inform patient care and potential future research to improve outcomes for young patients with MBC. Table 1: Median survival by disease presentation and subtype * 1 patient with recurrent MBC was not included because the initial diagnosis was DCIS MBC: metastatic breast cancer; OS: overall survival; CI: confidence interval; ER: estrogen receptor; PR: progesterone receptor; HER2: human epidermal growth factor receptor 2 Citation Format: Leticia Varella, Yue Zheng, Shoshana Rosenberg, Gregory Kirkner, Craig Snow, Kathryn Ruddy, Rulla Tamimi, Jeffrey Peppercorn, Lidia Schapira, Virginia Borges, Steven Come, Laura Collins, Ellen Warner, Kate Dibble, Eric Winer, Ann Partridge. Survival in Young Women with De Novo or Recurrent 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 PO5-05-14.

Abstract PS14-08: Safety evaluation from the KEYNOTE-355 study of pembrolizumab plus chemotherapy vs placebo plus chemotherapy in patients with previously untreated, locally recurrent inoperable or metastatic triple-negative breast cancer

Abstract Background: In KEYNOTE-355 (NCT02819518), pembrolizumab (pembro) + chemotherapy (chemo) led to statistically significant and clinically meaningful improvements in PFS and OS (primary endpoints) vs placebo (pbo) + chemo in patients (pts) with previously untreated PD-L1 positive advanced TNBC (combined positive score ≥10). In the overall safety population at final analysis, treatment-related AEs occurred in 96.3% of pts in the pembro + chemo arm and 95.0% of pts in the pbo + chemo arm; immune-mediated AEs occurred in 26.5% and 6.4% of pts, respectively. We report additional safety information, beyond the already reported safety results, on immune-mediated AEs and management from the final analysis of KEYNOTE-355. Methods: Eligible pts were randomized 2:1 to receive pembro 200 mg or pbo Q3W for up to 35 cycles + investigator’s choice of nab-paclitaxel, paclitaxel, or gemcitabine-carboplatin. Safety was assessed in all randomized pts who received ≥1 dose of study treatment. AEs were monitored throughout the study and for 30 d post-treatment (90 d for serious AEs). Results: At final analysis (data cut-off: June 15, 2021), median treatment duration was 6.1 (range, 0.0–48.8) mo in the pembro + chemo arm (n = 562) and 5.3 (range, 0.0–51.5) mo in the pbo + chemo arm (n = 281). Of 157 pts with immune-mediated AEs and infusion reactions in the pembro + chemo arm, 125 had grade 1-2 events and 32 had grade 3-4 events; none were grade 5. The most common immune-mediated AEs with pembro + chemo were hypothyroidism (15.8%) and hyperthyroidism (4.3%); infusion reactions occurred in 3.7% of pts (table). Of 89 pts with hypothyroidism, median time to onset was 105 d (range, 19–707 d) and 70 were treated with thyroid replacement, suggesting an endocrine abnormality and need for continued thyroid replacement. Of 24 pts with hyperthyroidism, median time to onset was 53.5 d (range, 20–209 d) and 2 were treated with corticosteroids. Of 21 pts with infusion reactions, median time to onset was 147 d (range, 1–729 d) and 10 were treated with corticosteroids. Other immune-mediated AEs of interest in the pembro + chemo arm were pneumonitis (2.5%) and adrenal insufficiency (1.4%); most of these events were grade 2–3. Of 14 pts with pneumonitis, median time to onset was 99.5 d (range, 29–288 d) and 11 were treated with corticosteroids; median episode duration was 56 d. All 8 pts with adrenal insufficiency were treated with hormone replacement. There were no reports of hypophysitis. Conclusion: In pts with previously untreated advanced TNBC, pembro + chemo had a manageable safety profile that was generally consistent with the known safety profiles of pembro and the chemo regimens. Most immune-mediated AEs and infusion reactions were grade 1-2, manageable with treatment interruption, corticosteroids, and/or hormone replacement therapy, and did not result in discontinuation of study treatment. Together with the efficacy findings, our results support pembro + chemo as a standard of care regimen for these pts. Table. Citation Format: Hope Rugo, Peter Schmid, Zbigniew Nowecki, David Cescon, Seock-Ah Im, Mastura Yusof, Carlos Gallardo, Hiroji Iwata, Carlos Barrios, Sherene Loi, Xuan Zhou, Xiaoli Zhang, Wilbur Pan, Vassiliki Karantza, Javier Cortés. Safety evaluation from the KEYNOTE-355 study of pembrolizumab plus chemotherapy vs placebo plus chemotherapy in patients with previously untreated, locally recurrent inoperable or metastatic triple-negative 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 PS14-08.

Abstract PO4-14-04: Comprehensive genomic profiling results in patients with metastatic breast cancer due to germline BRCA1/2 status and their HER2-low status

Abstract Objective: To determine the usefulness of comprehensive genomic profiling testing and the percentage of HER2-low in patients with germline BRCA1/2 (gBRCA1/2) variants metastatic breast cancer. Methods: We included 3404 patients with metastatic recurrent breast cancer who underwent CGP testing from June 2019 to June 2023 in Japan. We examined the proportion of patients with or without recommended therapy, the proportion of patients who received matched therapy, and the proportion of patients with HER2 low by gBRCA1/2 variant due to CGP testing. RESULTS.: Of the 3404 patients, 69 (2.0%) had gBRCA1, 136 (4.0%) had gBRCA 2, 5 (0.1%) had gBRCA1 &amp; gBRCA2, 1807 (53.1%) were negative, and 1388 (40.1%) were untested or unknown. The overall percentage of patients who recommended targeted therapy due to CGP testing was 37.4%(1272/3404), with gBRCA1 at 31.9%(22/69), gBRCA2 at 43.4%(59/136), and gBRCA1&amp;gBRCA2 at 50%(2/4). The percentage of matched therapy performed in the 1st line after the expert panel was 8.3% overall, 2.9% for gBRCA1, 14.0% for gBRCA2, and 0% for gBRCA1&amp;gBRCA2. The rate of tumor mutation burden (TMB) high was 7.4% overall, and gBRCA1 at 2 .9%, gBRCA2 at 9.6%, and gBRCA1&amp;gBRCA2 at 50%. On the other hand, the percentage of HER2-low was 38.3% overall, 29% for gBRCA1, 58.1% for gBRCA2, and 25% for gBRCA1 &amp; gBRCA2. Conclusion.: Germline BRCA2 variants had a higher rate of reaching matched therapy based on CGP test results. The higher rate of TMB high was suggested to be the reason for this. The high percentage of patients with HER2-low is also expected to improve the prognosis. Citation Format: Hiroshi Tada, Minoru Miyashita, Narumi Harada-Shoji, Yohei Hamanaka, Miku Sato, Mika Yanagaki, Satoko Tsunokake, Tokiwa Motonari, Tomomi Kon, Asumi Yamazaki, Takanori Ishida. Comprehensive genomic profiling results in patients with metastatic breast cancer due to germline BRCA1/2 status and their HER2-low status [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 PO4-14-04.

Abstract PO3-05-02: Impact of hormone receptor expression level in HR+/HER2- metastatic breast cancer in the large French ESME cohort

Abstract Background: In patients (pts) with early breast cancer (BC), the level of expression of estrogen receptor (ER) evaluated by immunohistochemistry is prognostic and predictive while progesterone receptor (PR) expression has an additional prognostic value. Allred scoring combines the percentage of positive cells and the intensity of staining. It is widely used for treatment choice for early BC. In metastatic setting, its role is less defined. Methods: The ESME database is a French National cohort of all consecutive pts who initiated a first-line treatment for metastatic BC (MBC) between January 2008 and December 2020 in one of the 18 French Comprehensive Cancer Centers (NCT03275311). For this study, we selected pts with HER2- MBC, known ER expression and intensity percentages, known PR status and who received endocrine-based therapy as first-line metastatic treatment. Primary objective was to evaluate the overall survival (OS) and first line progression-free survival (PFS1) under endocrine therapy according to ER and PR expression level. ER expression was defined using Allred score on the last available tumor sample. PR status was defined using a positive (≥10%)vs negative ( &amp;lt; 10%) threshold. Secondary objective was to evaluate clinical PFS1 whether de novo or recurrent MBC and according to type of first line therapy (mono- vs combined endocrine therapy). Results: In the ER+ ± PR+/HER2- population, 8269 pts had information on ER percentage and staining intensity. Median follow-up was 53.4 months (95%CI [51.9; 54.7]). Allred score distribution, OS and PFS1 are described in table 1. Median OS was 43.1 months [41.1; 45.0] for the PR- group compared with 52.3 months [50.5; 54.4] for the PR+ group. After adjustments, patients with a PR- tumour had still a worse prognosis (HR=1.20, 95%CI [1.12-1.28], p&amp;lt;0.001). Median PFS1 was 10.2 months[9.6; 10.8]and 14.8 months[14.2; 15.4] for pts with PR- vs PR+ tumour (HR=1.36 (1.29-1.43), p&amp;lt;0.001) and PR status remained significant prognostic factor independently of de novo or recurrent status and association or not with a targeted therapy. Conclusion: ER expression evaluated using the Allred scoring, as well as PR positivity, retain prognostic value in first-line MBC patients. Table 1 : OS and PFS according to Allred status, de novo status and type of endocrine therapy. * Selected variables on multivariate model include PR status, age, SBR grade, histological subtype, number of metastatic site, type of metastasis (non visceral, visceral, brain visceral), HER 2 (0 vs 1-2), metastatic-free interval, mono- vs combined endocrine therapy. Citation Format: Marie Alexandre, Florence Castan, Thibault De La Motte Rouge, Audrey Mailliez, Etienne Brain, Thomas Bachelot, Monica Arnedos, Florence Dalenc, Jean-Marc Ferrero, Vincent Massard, Isabelle Desmoulins, Marie-Ange Mouret-Reynier, Christelle Levy, Anthony Gonçalves, Anca Berghian, Aude-marie Savoye, Jean-Sébastien frenel, Lise Bosquet, Suzette Delaloge, William Jacot. Impact of hormone receptor expression level in HR+/HER2- metastatic breast cancer in the large French ESME cohort [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 PO3-05-02.

Abstract PO2-04-01: Predictors of exceptional response to first line HER2-targeted therapy for metastatic breast cancer

Abstract Background HER2-targeted therapies have transformed the trajectory of HER2-positive (HER2+) metastatic breast cancer (MBC), with a subgroup of responders remaining on first line (1L) therapy for many years (yrs). Despite these promising outcomes, the paradigm remains palliative, with some patients (pts) receiving therapy indefinitely. Opportunities to interrupt therapy are controversial and anecdotal in the setting of a limited understanding of long-term responders and lack of predictive biomarkers. Methods We identified prevalent pts with HER2+ MBC seen and consented at Dana-Farber Cancer Institute between 2010 and 2023, regardless of the original date of MBC diagnosis. Exceptional responders (ExRes) were pts without evidence of progressive disease (PD) 3 yrs from initiation of 1L therapy for MBC. Conventional responders (ConRes) were pts who experienced PD within 3 yrs of 1L treatment initiation. We compared clinicopathological characteristics and treatment patterns between ExRes and ConRes using Chi-square or Wilcoxon test. We analyzed median time to treatment switch due to PD (TTS-PD) – i.e., time from metastatic diagnosis to 1L treatment end due to PD - and overall survival, via the Kaplan-Meier method and with a landmark analysis at year 3 (Y3). Our primary aim was to identify predictors of exceptional response to 1L anti-HER2 therapy. Results Of 635 pts with HER2+ MBC, we identified 147 ExRes and 370 ConRes and excluded 118 pts due to follow up ≤ 3 yrs and no PD events. Median follow up was 7.1 yrs (IQR 5.5-11.0) for ExRes and 7.1 yrs (IQR 4.0-11.4) for ConRes. Median age at MBC diagnosis was 50.7 yrs (range 21.9-91.9) for ExRes and 49.8 yrs (26.9-82.3) for ConRes. ExRes presented more often with de novo MBC than ConRes (52.1 vs 30.6%, p&amp;lt; 0.0001). On metastatic samples, more ExRes than ConRes had HER2 3+ tumors by immunohistochemistry (IHC) (93.7 vs 81.0%, p=0.002), whereas the proportion of ER-positive disease was similar between the two groups (45.6 vs 53.4%, p=0.1). Most pts received (neo)adjuvant anti-HER2 agents in both groups (62.5 vs 72.7%, p=0.1). More ExRes than ConRes (55.8 vs 42.7% p=0.007) received 1L chemotherapy (CT) plus trastuzumab (H)/pertuzumab (P). Alternative 1L treatments were CT plus H (26.5 vs 25.7%), H +/- P +/- endocrine therapy (8.2 vs 10.5%), T-DM1 (2 vs 9.2%), tyrosine kinase inhibitors-based regimens (7.5 vs 10.8%). For pts with recurrent MBC, disease-free interval was longer for ExRes than ConRes (median 4.7 vs 3.4 yrs, p=0.01). Visceral involvement at MBC relapse was similar for ExRes and ConRes (78.2 vs 77.8%, p=0.9). Brain metastases at any timepoint were less frequent among ExRes than ConRes (42.9 vs 55.1%, p=0.01). Among ExRes, 70 (47.6%) pts experienced PD after Y3, with a median TTS-PD of 4.6 (4.1-5.1) yrs. In a landmark analysis at Y3, the 2-year TTS-PD was 68.5% (95% CI: 59.8%-75.7%) (5 yrs from treatment start), and 4-year overall survival was 86.5% (95% CI: 78.1%-91.9%) (7 yrs from treatment start). ConRes received a median of 5 (1-19) treatment regimens for MBC, with a median 1L TTS-PD of 12 (10.8-13) mo. A total of 89 (60.5%) ExRes and 214 (57.8%) ConRes underwent tumor sequencing. Data comparing genomic features between ExRes and ConRes will be presented. Conclusions In this prospective cohort, 28% of pts with HER2+ MBC had exceptional response to 1L anti-HER2 therapy. Consistent with prior data, ExRes present more frequently with de novo disease and HER2 IHC 3+ tumors. In our cohort, ExRes had a median follow-up of 7.1 years and 52.4% never experienced PD. Although a significant proportion of pts with HER2+ MBC derive long-term benefit from anti-HER2 therapy, the treatment paradigm remains palliative, and it is unknown whether biomarkers may reliably predict exceptional response and guide future treatment. Ongoing work will explore whether genomic features vary between ExRes and ConRes. Citation Format: Stefania Morganti, Tianyu Li, Katheryn Santos, Melissa Hughes, Nolan Priedigkeit, Yvonne Li, Marla Lipsyc-Sharf, Gregory Kirkner, Janet Files, Julie Kasparian, Elizabeth Grant, Gunjan Gupta, Giuseppe Curigliano, Sara Tolaney, Andrew Cherniack, Nabihah Tayob, Nancy Lin, Heather Parsons. Predictors of exceptional response to first line HER2-targeted therapy for 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 PO2-04-01.

Abstract PO1-06-12: Phase II study of sitravatinib plus tislelizumab with or without nab-paclitaxel in patients with locally recurrent or metastatic triple negative breast cancer

Abstract Background: The combination of a PD-(L)1 inhibitor plus chemotherapy demonstrated promising anti-tumor activity as first-line therapy for patients (pts) with locally recurrent inoperable or metastatic PD-L1 positive triple-negative breast cancer (TNBC). However, for pts without PD-L1 expression and for those who have failed prior lines of treatment, therapeutic options are still limited. This multi-cohort, phase II trial aimed to evaluate the safety and antitumor activity of 70 mg (cohort A) or 100 mg (cohort B) sitravatinib plus tislelizumab in pts with locally recurrent or metastatic TNBC, and their combination (70 mg sitravatinib plus tislelizumab) with nab-paclitaxel in untreated locally recurrent inoperable or metastatic TNBC pts (cohort C). The efficacy of sitravatinib plus tislelizumab in cohort A and B has been reported with objective response rate (ORR) of 38.1% and 45.0%, respectively. Herein, the preliminary results of cohort C and updated results of cohort A and B were reported. Methods: Pts with untreated locally inoperable or metastatic TNBC were included in cohort C and received 70 mg sitravatinib orally once daily plus 200 mg tislelizumab intravenously on day 1 and 100mg/m2 nab-paclitaxel on days 1 and 8 every three weeks until disease progression or intolerable toxicity. The primary endpoint was ORR. Secondary endpoints included disease control rate (DCR), progression-free survival (PFS), duration of response (DOR), 1-year overall survival (OS) rate and safety/tolerability. Based on Simon’s two-stage design, &amp;gt; 9 responders were need in stage 1 (n=18) for the study to continue, and &amp;gt;19 responders were needed by the end of study (n=35) to demonstrate statistical superiority with sitravatinib plus tislelizumab and nab-paclitaxel (assumed to be around 65%) to a historical control of 46% (1-sided alpha of 0.1, power of 80%). Updated analyses were provided for cohort A (Simon’s 2 stage design) and B (Bayesian optimal phase II design). Results: Among the 18 pts in stage 1 of cohort C, 12 of them achieved confirmed response, and therefore the study proceeded to the enrollment in stage 2. As of April 30, 2023, a total of 32 pts were enrolled, with a median age of 51 years. Among the 23 efficacy evaluable pts, unconfirmed ORR was 87.0% (95% CI 66.4-97.2) (including 3 CRs and 17 PRs), with 7 pts not reaching next tumor assessment after reaching CR/PR, and confirmed ORR was 52.2% (95% CI 30.6-73.2). DCR was 95.7%. Any grade of treatment-related adverse events (TRAEs) occurred in 31 (96.9%) pts, and grade ≥3 TRAEs occurred in 5 (15.6%) pts. One (3.1%) patient experienced grade ≥3 immune-related adverse events. SAEs were reported in 3 (9.4%) pts. At the data cut-off date, the median follow-up duration for cohort A and B was 20.4 (range 1.3–24.3) months and 13.3 (range 5.1-19.1) months, respectively. The median PFS in cohort A was 8.2 (95% CI 2.8-12.4) months, and in cohort B was 5.4 (95% CI 4.2-10.9) months. Median OS was not reached in both cohorts. RNA-seq analysis showed that the suppression of immune regulatory pathways and the activation of metabolic pathways promoted early progression. Besides, baseline angiogenesis associated pathway held the potential to predict the favorable response to tislelizumab plus sitravatinib. Conclusion: In the first-line treatment of locally recurrent or metastatic TNBC, preliminary analysis of cohort C showed that sitravatinib combined with tislelizumab and nab-paclitaxel had promising anti-tumor activity with a high ORR, and the combination was generally well tolerated. In TNBC pts with less than three lines of therapy, the chemotherapy-free regimen with sitravatinib plus tislelizumab demonstrated promising PFS after a longer follow-up duration. Citation Format: Lei Fan, Xiyu Liu, Ying Xu, Xinyi Sui, Wenjuan Zhang, Linxiaoxi Ma, Xi Jin, Song-Yang Wu, Han Wang, Yi Xiao, Li Chen, Jiong Wu, Ke-da Yu, Guangyu Liu, Xin Hu, Zhonghua Wang, Yi-Zhou Jiang, Zhi-Ming Shao. Phase II study of sitravatinib plus tislelizumab with or without nab-paclitaxel in patients with locally recurrent or metastatic triple negative 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 PO1-06-12.

Abstract GS01-05: Pembrolizumab + Olaparib vs Pembrolizumab + Chemotherapy After Induction With Pembrolizumab + Chemotherapy for Locally Recurrent Inoperable or Metastatic TNBC: Randomized Open-Label Phase 2 KEYLYNK-009 Study

Abstract Background: Pembrolizumab (pembro) plus chemotherapy (chemo) showed statistically significant improvements in PFS and OS vs placebo + chemo in patients (pts) with previously untreated locally recurrent inoperable or metastatic triple-negative breast cancer (TNBC) whose tumors expressed PD-L1 with a combined positive score (CPS) ≥10 in the phase 3 KEYNOTE-355 study. Tolerable and effective maintenance regimens after induction therapy are needed to sustain clinical benefit. The PARP inhibitor olaparib is an established maintenance therapy for multiple platinum-sensitive tumor types and prior data suggest that PARP inhibitors combined with PD-1/PD-L1 inhibitors could provide an improved therapeutic effect. KEYLYNK-009 (NCT04191135) is a randomized open-label phase 2 study to evaluate the efficacy and safety of maintenance pembro + olaparib vs pembro + chemo in pts with locally recurrent inoperable or metastatic TNBC who had clinical benefit from induction with 1L pembro + platinum-based chemo. Methods: Eligible pts with measurable, locally recurrent inoperable or metastatic TNBC that had not been previously treated with chemo in the metastatic setting received induction therapy for up to 6 cycles of pembro 200 mg + chemo (carboplatin AUC 2 + gemcitabine 1000 mg/m2 on days 1 and 8) every 3 wk (Q3W). Pts with complete response (CR), partial response (PR), or stable disease (SD) after 4-6 treatment cycles were randomized 1:1 to receive pembro 200 mg Q3W + olaparib 300 mg twice daily or pembro + chemo (continued induction regimen). Olaparib or chemo was continued until progression or unacceptable toxicity; pembro was continued for up to 35 cycles (including induction treatment), progression, or unacceptable toxicity. Pts were stratified by induction response (CR or PR vs SD, by RECIST v1.1), tumor PD-L1 status (CPS ≥1 vs CPS &amp;lt; 1), and tumor genomic status (tBRCAm vs tBRCAwt). Dual primary endpoints were PFS per RECIST v1.1 by BICR and OS from randomization in all pts. Secondary endpoints included PFS and OS from randomization in pts with PD-L1 CPS ≥10 tumors and in pts with tBRCAm, and safety. Results: Of the 460 pts who received induction therapy, 271 were randomly assigned to pembro + olaparib (n=135) or pembro + chemo (n=136). At the Dec 15, 2022 data cutoff, median follow-up was 17.2 mo. Maintenance pembro + olaparib did not significantly improve PFS or OS vs pembro + chemo after induction therapy (Table). Median PFS was longer with pembro + olaparib vs pembro + chemo in pts with tBRCAm, but not in pts with PD-L1 CPS ≥10 tumors; a similar trend was observed for OS (Table). In 268 treated pts, treatment-related AEs (TRAEs) occurred in 114 of 135 pts (84.4%) for pembro + olaparib and in 128 of 133 pts (96.2%) for pembro + chemo. Grade ≥3 TRAEs occurred in 44 pts (32.6%) for pembro + olaparib (0 deaths) and in 91 pts (68.4%) for pembro + chemo (2 [1.5%] deaths), with 12 (8.9%) vs 26 (19.5%) discontinuations for TRAEs, respectively. Conclusions: The primary endpoints of PFS and OS were not met in an unselected population of pts with advanced TNBC. However, directionally favorable improvements in PFS and OS were observed in pts with tBRCAm with pembro + olaparib vs pembro + chemo, representing a potential maintenance strategy. Further data are required to confirm this effect. No new safety signals were observed, and there were fewer TRAEs in the pembro + olaparib group vs the pembro + chemo group. PFS and OS were evaluated from the time of randomization. *Based on stratified Cox regression model with Efron’s method of tie-handling with treatment as a covariate. NR = not reached. Citation Format: Hope Rugo, Mark Robson, Seock-Ah Im, Florence Dalenc, Eduardo Yañez Ruiz, Young-Hyuck Im, Sergii Kulyk, Oleksandr Dudnichenko, Néstor Llinás-Quintero, Shigehira Saji, Yasuo Miyoshi, Nadia Harbeck, Li Fan, Jaime Mejia, Vassiliki Karantza, David Cescon. Pembrolizumab + Olaparib vs Pembrolizumab + Chemotherapy After Induction With Pembrolizumab + Chemotherapy for Locally Recurrent Inoperable or Metastatic TNBC: Randomized Open-Label Phase 2 KEYLYNK-009 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 GS01-05.

Abstract PO2-23-12: Innovative Metastatic Breast Cancer Therapy, CBT300, Reverses Drug and Immune Resistance

Abstract For many patients with metastatic breast cancer (MBC), their disease is treatable but incurable. Although the rate of death from MBC has significantly decreased over the last 10 years due to early detection and new treatment options, MBC still accounts for over 40,000 deaths each year in the US that has been consistent for the past 30 years. Recently, it is estimated that 90% of those deaths were due to drug resistant recurrent disease. Nearly 45% of MBC deaths can be attributed to a subpopulation of patients with metastatic triple negative breast cancer (mTNBC). Despite MBC’s initial sensitivity to chemotherapy, it often recurs at greater than 40% in stage I-III patients and greater than 80% in stage IV patients which have a dismal 5-year survival of 12%. African American women have a 40% greater incidence of death from MBC despite a 4% lower risk of diagnosis. Unfortunately, current therapies do little to reduce drug resistance and death for recurrent drug resistant MBC. Currently, the only therapies approved by the FDA for recurrent TNBC patients are Keytruda plus chemotherapy and an Antibody Drug Conjugate (ADC) called Sacituzumab Govitecan. Keytruda (anti-PD-L1) is an immune checkpoint inhibitor(ICI) given with chemotherapy (nab-paclitaxel, paclitaxel, or gemcitabine plus carboplatin). The second recently approved therapy, Sacituzumab Govitecan (SG), is composed of an antibody to human trophoblast cell-surface antigen 2 (Trpo-2) coupled to SN-38 (topoisomerase I inhibitor). Although these results are very encouraging, the 80% of TNBC patients that either do not have high positive PD-L1 tumors, or don’t respond to these therapies and become drug resistant suggests that most patients with TNBC will have recurrent disease with little or no hope for survival. For contrast, our novel MBC therapy, CBT300, targets cell surface GRP78 that has been found in over 95% of MBC and in 93% of TNBC tumors. We can now show that inhibition of cell surface GRP78 can a) induce apoptosis of drug resistant TNBC cells in vitro and in vivo, b) eliminate drug resistance showing synergistic effects with chemotherapy in vitro and in vivo, c) decrease amount of chemotherapy in combination with CBT300 and d) reduce immune suppression. Recent publications show that GRP78 is found on many types of tumor cell surfaces but not on normal cell surfaces. In fact, tumor cell surface GRP78 (csGRP78) is important for many aspects of MBC development, including cell survival, proliferation, chemoresistance, angiogenesis, metastasis formation, immune suppression, and stem cell formation. Recently, it has been shown that increased cell surface GRP78 expression in TNBC patients was significantly associated with later stage, increased distant metastasis, increased aggressiveness, shorter disease-free survival, and decreased overall survival. In studies to help understand how cell surface GRP78 causes MBC progression and drug resistance, we discovered a novel GRP78 binding transmembrane protein on TNBC cells called Receptor Tyrosine Kinase Orphan Receptor-1 (ROR1). Using the GRP78 binding domain from ROR1 and a human Fc IgG1 domain, we created a biologic fusion protein that is a potent and cell surface specific GRP78 inhibitor, CBT300. We now show that CBT300’s elimination of cell surface GRP78 destabilizes and removes oncofetal proteins ROR1, Cripto-1, and checkpoint protein PD-L1 from tumor cell surfaces resulting in reversal of chemoresistance, reduction in immune suppression, inhibition of stem cell phenotype and increased tumor cell apoptosis. Since ROR1, Cripto-1 and PD-L1 are three of the major redundant pathways for tumor drug resistance, immune suppression and stem cell formation, the ability to inhibit all these pathways with CBT300, a single safe and very efficacious therapy, is very innovative and could be a significant advance for the treatment of MBC. Citation Format: Elizabeth Stolarik, Jorryn Zelek, Mariah Thigpen, Anita Davidson, Donald Davidson. Innovative Metastatic Breast Cancer Therapy, CBT300, Reverses Drug and Immune Resistance [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 PO2-23-12.

Pembrolizumab plus chemotherapy for first-line treatment of advanced triple-negative breast cancer.

Aim: A systematic review and network meta-analysis (NMA) was performed to evaluate the efficacy of first-line treatments for locally recurrent unresectable or metastatic triple-negative breast cancer (TNBC) patients.Materials & methods: Databases were searched for randomized controlled trials evaluating first-line treatments for locally recurrent unresectable or metastatic TNBC patients. NMA was performed to estimate relative treatment effects on overall and progression-free survival between pembrolizumab+chemotherapy and other interventions.Results: NMA including eight trials showed that the relative efficacy of pembrolizumab+chemotherapy was statistically superior to that of other immunotherapy- or chemotherapy-based treatment regimens.Conclusion: Pembrolizumab+chemotherapy confers benefits in survival outcomes versus alternative interventions for the first-line treatment of locally recurrent unresectable or metastatic TNBC patients.

Abstract 5266: Deciphering the systemic immune effects of abemaciclib in recurrent metastatic breast cancer: A multicenter, prospective study

Abstract Background: Abemaciclib, a CDK4/6 inhibitor, stands as a cornerstone for managing hormone receptor-positive, HER2-negative advanced or metastatic recurrent breast cancer. It is known to modulate the tumor immune microenvironment, enhancing anti-tumor responses. Yet, its systemic immunological impact remains to be elucidated. This investigation aims to delineate the influence of abemaciclib on both the gut microbiota and the systemic immune landscape in patients with breast cancer. Methods: A multicenter, prospective clinical trial was conducted involving 40 patients with hormone receptor-positive, HER2-negative advanced or metastatic recurrent breast cancer, scheduled for abemaciclib therapy. The trial's primary objectives were to evaluate the duration of treatment efficacy and the severity of gastrointestinal toxicity. Secondary objectives included assessing the interplay between circulating immune profiles, gut microbiota, and clinical outcomes. Patient samples, including peripheral blood mononuclear cells (PBMCs) for single-cell RNA sequencing and stool for 16S rRNA gene analysis, were collected at baseline and after 90 days of treatment initiation. Results: This interim report presents findings from 39 patients. We examined 75 PBMC samples and 78 stool samples. Preliminary analysis indicated that abemaciclib precipitated an upregulation of cytokines pivotal for anti-tumor immunity, notably IL-7 and IP-10, alongside an activation of circulating innate immune cells such as CD4-positive T cells and dendritic cells. Concurrently, gut microbiota analysis revealed a post-treatment reduction in alpha diversity, with notable shifts in microbial populations implicated in innate immune activation. Discussion: This study presents novel insights into the systemic immunomodulatory effects of abemaciclib. Our results suggest that abemaciclib's therapeutic efficacy may partially derive from its ability to alter the circulating immune profile and gut microbiota. These findings could pave the way for innovative immunotherapeutic approaches, integrating gut microbiome considerations into the treatment of hormone receptor-positive, HER2-negative breast cancer. Citation Format: Yukiko Fukui, Kosuke Kawaguchi, Yurina Maeshima, Yuri Fujimoto, Hiroshi Ishiguro, Kazuhiko Yamagami, Sachiko Takahara, Hirofumi Suwa, Masae Torii, Shigenori Nagai, Yasuaki Sagara, Wakako Tsuji, Hiroyasu Yamashiro, Takeshi Kotake, Shinji Fukuda, Kuniaki Saito, Yasuko Yamamoto, Masako Kataoka, Yuki Himoto, Atsushi Yonezawa, Yuki Nakamura, Wei Li, Sunao Tanaka, Satoshi Morita, Masahiro Takada, Masakazu Toi. Deciphering the systemic immune effects of abemaciclib in recurrent metastatic breast cancer: A multicenter, prospective study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5266.

Abstract 174: Cholesterol efflux protein ABCA1 skews macrophages towards an anti-tumor phenotype and consequently impacts breast cancer progression

Abstract With a lifetime risk of approximately 1 in 8, breast cancer maintains in its position as the most prevalent form of cancer and ranks second in terms of cancer-related fatalities in women. The primary cause of mortality is often attributed to the recurrence of metastatic breast cancer. While immune therapy shows some effectiveness, many patients do not exhibit meaningful responses, likely due to immune-suppressive factors present within the tumor microenvironment. These factors include myeloid cells such as Macrophages(MΦ), therefore, there is a strong need to devise strategies to shift (MΦ) from a pro-tumor to an anti-tumor phenotype. Our previous research has uncovered the susceptibility of MΦs to disruptions in cholesterol metabolic balance. Considering these findings, coupled with epidemiological evidence linking elevated plasma cholesterol to unfavorable prognosis, the impact of cholesterol homeostasis in tumor associated MΦs on breast cancer becomes evident. An in-depth computational screen helped us identify ABCA1—a cholesterol efflux protein with elevated mRNA expression associated with increased survival. Beyond cholesterol efflux, ABCA1 also facilitates the movement of cholesterol from the inner membrane layer to the outer layer. Previous work has shown that cholesterol within the inner membrane layer can directly interact with and activate various receptors on the membrane's surface, initiating downstream signaling events. Consequently, the activities of ABCA1 in cholesterol efflux and translocation likely hold substantial regulatory implications. Underscoring the clinical significance of ABCA1 are our findings that heightened ABCA1 expression within breast tumors correlates with augmented levels of cytotoxic T cells, T cell effector enzymes (Prf-1 and Gzmb), and improved survival rates. Crucially, our in vitro investigations indicate that ABCA1 modulates multiple functions of MΦs to adopt an anti-cancer phenotype, encompassing: (1) the ability to infiltrate tumor spheroids, (2) angiogenesis, (3) efferocytosis—an immune-suppressive phagocytic process devoid of antigen presentation, and (4) the expansion, migration, and activity of cytotoxic T cells. ABCA1 transports cholesterol from macrophages to a lipid poor ApoA1 protein and facilitates the formation of nascent HDL via reverse cholesterol transport. We leveraged this mechanism to therapeutically target ABCA1 using ApoA1 mimetics 5A and 4F. Our data so far indicates that these ApoA1 phenocopy ABCA1 overexpression in MΦs. Together, our data provides compelling evidence for the involvement of ABCA1 in the pathophysiology of breast tumors. The anticipated outcomes of this research will establish the basis for the future utilization of ABCA1 and its downstream effects for therapeutic purposes. Citation Format: Shruti V. Bendre, Natalia Krawczynska, Shaunak Bhogale, Erin Weisser, Simon Han, Basel Hajyousif, Avni Singh, Rajendra K C, Yu Wang, Claire P. Schane, Adam T. Nelczyk, Anasuya DasGupta, Hashni E. Gamage, Kevin T. VanBortle, Emad Tajkhorshid, Saurabh Sinha, Wohnwa Cho, Erik R. Nelson. Cholesterol efflux protein ABCA1 skews macrophages towards an anti-tumor phenotype and consequently impacts breast cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 174.

Late-Onset Myasthenia Gravis in a Patient with Recurrent Breast Cancer: A Case Report

Introduction: Myasthenia gravis (MG) is an autoimmune disorder characterized by fatigable weakness, typically affecting voluntary muscles. Myasthenia gravis as a paraneoplastic syndrome (PNS) of a thymoma is well known, but it is rare to have MG PNS due to extrathymic neoplasms. Case: We present a case on an 80-year-old female who was diagnosed with myasthenia gravis in the presence of recurrent metastatic breast cancer. Discussion: The question remains whether MG is truly a neoplastic syndrome of breast cancer, or if older individuals are more likely to suffer from both breast cancer and late-onset myasthenia gravis (LOMG) at the same time. It was found that those diagnosed with LOMG are more likely to have extrathymic neoplasms. Regardless, the underlying malignancy should be treated, MG treatment should be initiated, and if PNS is suspected immunosuppressants are indicated. Conclusion: This case highlights the complexity of classifying MG in elderly patients with a concomitant neoplasm, but nonetheless, MG as a PNS of breast cancer remains a possibility.

A Case Report on Prolonged Response with Trastuzumab Emtansine (T-DM1) in Recurrent Advance Breast Cancer Setting

Breast cancer holds the dubious distinction of being the most prevalent malignant tumor among women worldwide the 5 year survival rate for patients with advanced or metastatic forms of the disease is estimated at a mere 23%, with approximately 20% of cases exhibiting an amplification of the human epidermal growth factor receptor 2 (HER2). HER2 overexpression was linked to a dismal prognosis prior to the advent of targeted HER2 therapies. The introduction of ado-trastuzumab emtansine (T-DM1) has emerged as one of the standard treatment options for HER2-positive breast cancer patients who experience a recurrence or progression of the disease. This case concerns a patient with recurrent metastatic breast cancer who achieved an unusually extended period of time without the disease progressing while on T-DM1 treatment. After experiencing disease progression on multiple treatment lines involving trastuzumab, the patient achieved a nearly complete clinical remission (cCR) with T-DM1 therapy. The availability of cost-effective biosimilars has expanded access to advanced biologic therapies, which were previously limited to a small segment of the population due to the cost barrier.

Characteristics and post-metastasis survival of recurrent metastatic breast cancer over time – An Australian population-based record linkage study, 2001–2016

AimTo assess population-level characteristics and post-metastasis survival of people with recurrent metastatic breast cancer (rMBC) during a period when new publicly-subsidised adjuvant and metastatic systemic therapies became available. MethodsRecord linkage study of females in NSW Cancer Registry (NSWCR) diagnosed with non-metastatic breast cancer (BC) in 2001–2002 (C1) and 2006–2007 (C2). We identified first rMBC from NSWCR, administrative hospital records, dispensed medicines and radiotherapy services (2001–2016). We used death registrations to estimate cumulative incidence of BC death. ResultsThe analysis included 2267 women with rMBC (C1:1210, C2:1057). Compared to C1, C2 had access to adjuvant HER2-targeted therapy and were more likely to have received adjuvant chemotherapy (C1:38%, C2:47%) and aromatase inhibitors (C1:52%, C2:73%, of those dispensed endocrine therapy). Five-year probability of BC death was 65% (95%CI:62–68%) in C1 and 63% (95%CI:60–66%) in C2. Regional disease (T4 or N + ) at initial BC diagnosis (C1:62%, C2:68%), and age ≥ 70 years at first metastasis (C1:27%, C2:31%) were more common in C2 and had poorer prognosis. Five-year probability of BC death was lower in C2 than C1 for treatment-defined HER2-positive BC (C1:72% 95%CI:63–79%; C2:52% 95%CI 45–60%) and those dispensed chemotherapy alone (C1:76% 95%CI:69–82, C2:67% 95%CI:59–74%, p = 0.01), but not treatment-defined hormone receptor-positive HER2-negative BC (C1:60% 95%CI 56–63%, C2:64% 95%CI 60–68%). ConclusionsDespite less favourable prognostic characteristics in C2, BC-related survival following rMBC was similar between the two cohorts; and improved for women with HER2-positive tumours. These findings support the real-world benefits of newer treatments for rMBC.