Background: Obesity may negatively affect survival in breast cancer (BC), but studies are conflicting, and associations may vary by tumor subtypes and race/ethnicity groups.
Methods: In a retrospective review, we identified 273 women with invasive BC administered Adriamycin/Taxane-based neoadjuvant chemotherapy from 2004 to 2016 with body mass index (BMI) data at diagnosis. Obesity was defined as BMI ≥30. Associations between obesity and event-free survival (EFS), using STEEP events, and overall survival (OS), using all-cause mortality, were assessed overall and stratified by tumor subtype [[Hormone Receptor Positive (HR+)/HER2-, HER2+, and Triple-Negative Breast Cancer (TNBC])] in our diverse population.
Results: Median follow-up was 32.6 months (range 5.7-137.8 months). Overall, obesity was associated with worse EFS (HR 1.71, 95% CI 1.03-2.84, p = 0.04) and a trend towards worse OS (p = 0.13). In HR+/HER2- disease (n = 135), there was an interaction between obesity and hormonal therapy with respect to OS but not EFS. In those receiving tamoxifen (n = 33), obesity was associated with worse OS (HR 9.27, 95% CI 0.96-89.3, p = 0.05). In those receiving an aromatase inhibitor (n = 89), there was no association between obesity and OS. In TNBC (n = 44), obesity was associated with worse EFS (HR 2.62, 95% CI 1.03-6.66, p = 0.04) and a trend towards worse OS (p = 0.06). In HER2+ disease (n = 94), obesity was associated with a trend towards worse EFS (HR 3.37, 95% CI 0.97-11.72, p = 0.06) but not OS. Race/ethnicity was not associated with survival in any subtype, and there were no interactions with obesity on survival.
Conclusions: Obesity may negatively impact survival, with differences among tumor subtypes.
Keywords: Breast cancer; Neoadjuvant chemotherapy; Obesity; Race/ethnicity; Survival; Tumor subtype.