Abstract P3-07-27: Patterns of chemotherapy (CT) use by molecularly-defined subtype among a population-based cohort of breast cancer (BC) patients (pts) from California:

Background: Guidelines describe recommended BC treatments (tx) according to tumor subtype; however, population-based data regarding tx utilization are limited. Objective: To describe tx utilization by tumor HER2, hormone receptor (HR) status, and stage among representative pts from California. Methods: We examined patterns of CT (including biologic tx) reported as received for all 131,450 female BC pts diagnosed with primary invasive BC in California between 1/1/2005 and 12/31/2011 in the California Cancer Registry, including n=19,918 HER2+ [65% HR+, 33% HR-]; n=91,919 HER2- [84% HR+, 15% HR-]; and n=19,613 HER2 unknown. Neoadjuvant & adjuvant CT data was only available for a subset of 35,040 pts diagnosed 2010-2011 (4,609 HER+; 27, 604 HER2-). Descriptive statistics were used for comparisons. Results: CT was reported as highest among pts with metastatic breast cancer (MBC) and HER2+ status (Table 1). The proportion of pts with early BC (EBC) receiving CT increased from 58% in 2005 to 69% in 2010, but was generally steady for MBC pts (74.2% in 2005 to 79.6% in 2011). 20.7% of HER2+ pts received neoadjuvant CT vs 8.6% for HER2- pts. Similarly, adjuvant CT was more common in HER2+ (55.5%) than HER2- (28.5%) pts. As expected the proportion of pts receiving CT was lower in HR+ vs HR- pts for EBC and MBC [eg. all stages HER2+ (62% vs 71%); HER2- (33% vs 68%)]. Conclusion: In this population-based cohort, ∼20-40% of MBC pts may not have received any CT or biologics. CT was more commonly received by HER2+ patients compared to HER2- patients for both EBC and MBC. Citation Format: Christina A Clarke, Laura Chu, Lisa Wang, Chunyan Song, Marjorie Green, Lisa Moy, Juan Yang, Li Tao, Scarlett Lin Gomez. Patterns of chemotherapy (CT) use by molecularly-defined subtype among a population-based cohort of breast cancer (BC) patients (pts) from California [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P3-07-27.