PIK3CA mutations are associated with lower rates of pathologic complete response to anti-human epidermal growth factor receptor 2 (HER2) therapy in primary HER2-overexpressing breast cancer

Abstract

Results: Overall, 21.4% of the patients harbored a PIK3CA mutation. Detection of a PIK3CA mutation was significantly associated with a lower pCR rate (19.4% with PIK3CA mutation v32.8% with PIK3CA wild-type; odds ratio [OR], 0.49; 95% CI, 0.29 to 0.83; P =.008). In the 291 hormone receptor (HR)-positive tumors, pCR rate was 11.3% with a PIK3CA mutation compared with 27.5% with PIK3CA wild-type (OR, 0.34; 95% CI, 0.15 to 0.78; P =.011). In 213 patients with HR-negative tumors, pCR rate was 30.4% with PIK3CA mutation and 40.1% without (OR, 0.65; 95% CI, 0.32 to 1.32; P =.233; interaction test P=.292). In multivariable analysis, HR status and PIK3CA status provided independent predictive inform..