The effect of trastuzumab on pCR in locally advanced HER2-positive breast cancer.

Abstract

286 Background: Neoadjuvant therapy (NAT) is now standard of care for locally advanced breast cancer (LABC). Evidence shows that pathological complete response (pCR) predicts for disease free and overall survival. The pCR rates for LABC vary widely in the literature but prognosis still remains poor for this group of pts. Increases in pCR have been reported in clinical trials with the addition of trastuzumab (T) but these studies have predominantly included operable pts. The aim of this study was to evaluate whether the addition of T to NAT has improved the rates of pCR in HER2+ LABC pts at our center. Methods: Pts from the LABC prospective database at the Sunnybrook Odette Cancer Center in Toronto were included if they had confirmed HER2+ LABC [primary tumors greater than 5cm (T3) with skin or chest wall involvement (T4) or with matted axillary adenopathy (N2)]. Two cohorts of LABC pts, pre-T and post-T groups were compared for baseline characteristics and pCR. Chi square tests and p values were used for comparing proportions. Results: 43 pts were diagnosed between Jan 2002 to Dec 31, 2006 who had HER2+ breast cancer and received NAT without T (pre-T cohort). 17 HER2+ pts were diagnosed with LABC between Jan 1, 2007 to Dec 31, 2009 who received neoadjuvant T (post-T cohort). Baseline characteristics were similar in two cohorts (Table) except more pts in pre-T cohort received neoadjuvant hormonal therapy. The rate of pCR in the pre-T cohort was 9.3% and in the post-T cohort 29% (p value=0.02). Conclusions: The pCR rate dramatically improved in our LABC patients with the addition of T to NAT. The pCR rates still remain lower than in published clinical trials likely reflecting the more advanced nature of LABC in clinical practice. [Table: see text]