Abstract P1-13-14: Triple positive breast cancer ; a distictive subtype and consideration of systemic therapeutic approach

Abstract

Abstract Introduction: Triple positive breast cancer is one of intrinsic subtype in breast cancer that is defined namely, ER/PR/Her2 positive tumors. It has multiple strategies for systemic therapy according to the characteristics of hormonal and anti-HER2 responsiveness. Each targeted therapy plays cross-talks between HER-2 and estrogen receptor signaling pathway resulting in endocrine resistance and anti Her2 resistance. Methods: We compared the triple positive subtype to the other breast cancer intrinsic subtypes to distinguish the uniqueness in their position among other breast cancer subtypes using retrospective analysis of two different cohorts; Korea Breast Cancer Society (KBCS) Breast cancer registry data (N=31266, Jan. 2006 – Dec. 2010) and database from St. Mary`s hospital Breast cancer registry (N=2216, Apr. 2009 – Mar. 2016). Results: Median follow up duration of 76 months in KBCS cohort (2006-2010) showed the overall survival graph of triple positive breast cancer located in the middle in between Luminal A intrinsic subtype and HER2 enriched subtype(P<.001). Also HER2 directed trastuzumab therapy did not improve the overall survival in triple positive breast cancer patients (P=.899) in contrast to the improved overall survival using trastuzumab therapy in HER2 enriched subtype (P=.018). Like the preceding results, CMC breast cancer data showed the similar results in recurrence free survival (P<.001). and no recurrence free survival improvement using trastuzumab therapy in triple positive breast cancer patient during the median follow up of 33 months (P=0.800). Conclusion: 1) Anti-HER2 therapy seems less beneficial in Triple positive breast cancer subtype regardless of breast cancer stage. 2) Triple positive breast cancer may require different therapeutic approaches 3) Other targeted agents (mTOR inhibitor, CDK4/6 inhibitor, PIK3CA inhibitor) can be a substitute option for the Trastuzumab therapy in triple positive breast cancer. Citation Format: Kim JS, Kim YS, You SH. Triple positive breast cancer ; a distictive subtype and consideration of systemic therapeutic approach [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-13-14.