Abstract PO3-06-10: Real World Outcomes with Sacituzumab Govitecan in Metastatic Triple Negative Breast Cancer Patients: A Multi-Institution Study

Abstract Background Sacituzumab govitecan (SG) is approved for treatment of metastatic triple negative breast cancer (mTNBC) in the second line and beyond. Little is known about the real-world outcomes of SG. We aim to evaluate the real-world effectiveness and toxicity outcomes of SG in heterogenous heavily pretreated mTNBC patients (pts) to investigate the consistency of the outcomes in comparison to the clinical trial population. Methods A multi-center retrospective study of pts with mTNBC treated with SG in the US from January 2021 until May 2023 was conducted. Demographics and clinicopathological variables including site of metastases, prior lines of therapy, relative dose intensity (RDI), adverse events (AEs), HER2 immunohistochemistry (IHC) score at time of metastasis, clinical response, clinical benefit rate (CBR) defined as (complete response, partial response (PR) or stable disease (SD) 6 months) and last follow-up were collected. For continuous variables, Mann-U Whitney and Kruskal Wallis tests were used to compare mean, median, standard deviation, and range. For categorical variables, Fisher's exact tests and Pearson Chi-square tests were used. Univariate and multivariate cox regression models examined RDI and survival outcomes. SAS v9.4 was used to perform statistical analysis at a significance level of 0.05. Results A total of 111 pts were analyzed. The median age was 58 years (range 29-84). The majority of pts were heavily pretreated: 59.1% received 3 prior lines of treatment (Tx) in the metastatic setting, 54.1% received prior immune checkpoint inhibitor (ICI), 8.1% received prior olaparib. 55% of pts had significant disease burden defined by =3 organs involved by metastatic disease, with 22.5% having brain metastasis at the time of initiation of SG. Of note, 51% had primary refractory disease defined as relapse within 12 months of completion of adjuvant chemotherapy. 98.1% experienced any grade AEs, with the most common being anemia 63.1%. Grade 3 AEs occurred in 51.4% pts with neutropenia being the highest 32.4% followed by anemia 14.4%, diarrhea 7.2% and fatigue 7.2%. Tx interruptions and dose reductions due to AEs occurred in 52.3% of patients and Tx discontinuation rate due to AEs was 11.8%. Elderly pts (defined as 65 years) did not have higher rates of dose reductions due to AEs compared to young pts ( = 65 years) (37.8% vs 59.7 %), p=0.043). The median RDI is 92% (interquartile range (IQR) 33%-100%). The median RDI in elderly pts was 94% (IQR 50%-100%). Among pts in which response was assessed, objective response rate (ORR) was 26.6% (25 pts had PR), and 38.3% had SD. Interestingly, the rate of alopecia was higher in pts who had PR as the best response (28%), compared to 5.6% in pts who had SD, and 3% in progressive disease (PD) p=0.004. The median prior line of therapy in pts who had PR and SD as best response was 2 (IQR 1, 5) (IQR1, 12), respectively, compared to a median of 3 (IQR 1, 7) in pts with PD, p 0.001. The CBR was 49% (46/94). The median duration of clinical benefit was 7 months IQR (2, 16) with median overall survival of 13 months IQR (2.5, 39) compared to 5.7 months IQR (0.03, 27) in pts without clinical benefit (p 0.001). 56.9% (62/109) of pts had HER2 low disease and the clinical benefit rate in this subgroup was 14.3% (23/62). Conclusion: In a heavily pretreated cohort, SG retains clinical activity and tolerability in mTNBC. This is reassuring given pts on clinical trials tend to be healthier compared to real-world clinical practice. Citation Format: Sabah Alaklabi, Arya Mariam Roy, Paola Zagami, Nicole Held, Saba Shaikh, Lubna Chaudhary, Yara Abdou, Shipra Gandhi. Real World Outcomes with Sacituzumab Govitecan in Metastatic Triple Negative Breast Cancer Patients: A Multi-Institution Study abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-06-10.