Efficacy of adjuvant trastuzumab (T) compared with no T for patients (pts) with HER2-positive breast cancer and tumors ≤ 2cm: A meta-analysis of the randomized trastuzumab trials.

508 Background: Adjuvant T plus chemotherapy improves disease-free survival (DFS) and overall survival (OS) vs. chemotherapy alone for pts with early stage HER2-positive breast cancer. We conducted a meta-analysis to estimate DFS and OS for pts with small tumors (≤2cm) in the T arms from 5 of the 6 randomized adjuvant trastuzumab trials. Pts with tumors ≤2cm, with 0 or 1 positive lymph nodes, and hormone receptor (HR) positive disease had a 5-year DFS of 91% and a 5-year OS of 97% (O’Sullivan, SABCS 2013; abstract:1327). We now plan to conduct an additional meta-analysis to assess the efficacy of T compared with no T for pts with small tumors (≤2cm). Methods: Six randomized controlled trials (RCT) were identified by a Medline search from 2004-2013. Trial groups from 5 phase III RCTs provided data (HERA, NCCTG N9831, NSABP B31, PACS 04, and FinHER).In total, 11,200 pts were randomized in these 5 trials;4,220 of whom had ≤2cm tumors, and known number of positive axillary lymph nodes and HR status(2,588 rand...