Abstract PD6-05: A prospective evaluation of clinical outcomes in women with pregnancy-associated breast cancer (PABC)

Background: Many studies suggest that women with PABC- breast cancer (BC) diagnosed during pregnancy or within 12 months post partum- have adverse outcomes compared to age matched women whose BC is not associated with pregnancy (non-PABC). However, it is unclear whether this is due to diagnostic delay alone or biological differences. Hence, we investigated whether PABC is independently prognostic for disease-free survival (DFS) and overall survival (OS) in a prospective database of young BC patients. Methods: A prospective database of women ≤40 years of age diagnosed with BC between February 2008 and January 2015 was analyzed. Data regarding, stage at diagnosis, pathology, treatment, and clinical outcomes were available. Statistically significant differences in baseline characteristics and administered therapies in women with and without PABC were evaluated using the chi-square or Fisher9s Exact tests. Kaplan-Meier curves for DFS and OS in the PABC and non-PABC cohorts were compared using the log-rank test. A multivariate Cox proportional hazards model adjusted for age, nodal involvement and tumor size. Results: Of 224 women in the database who provided consent for research, 32 (12%) had PABC. Mean age of the PABC and non-PABC patients respectively was 34 (range 27 to 39) and 37 (range 21 to 40) and the median follow-up was 40 months in both groups. PABC was more likely to be locally advanced at diagnosis (44% vs. 22%, p Eight patients (22%) in the PABC group and 19 (10%) in the non-PABC group experienced local or distant disease recurrence; 3 patients (8%) in the PABC group and 11 (6%) in the non-PABC group died. The 3-year DFS in the PABC and non-PABC cohorts was 79% vs. 90% (p=0.22) and the 3-year OS was 97% in both groups. Conclusion: Diagnostic delay could account for the higher rate of locally advanced disease in the PABC group. However, the lower hormone receptor expression and strong trend toward greater lymph node involvement independent of size suggest that women with PABC may have intrinsically worse disease biology. Event rates may still be too low to detect a statistically significant difference in recurrence risk. Further research is necessary to identify unique molecular features of PABC that may be amenable to targeting. Citation Format: Jerzak KJ, Zhu S, Li N, Mandel R, Warner E. A prospective evaluation of clinical outcomes in women with pregnancy-associated breast cancer (PABC) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr PD6-05.