Adjuvant capecitabine for invasive lobular/mixed early breast cancer (EBC): USON 01062 exploratory analyses.

547 Background: Randomized phase III USON 01062 trial determining if patients with EBC would benefit from addition of capecitabine to docetaxel after AC (AC-T vs AC-XT). AC-T: docetaxel 100mg/M2 IV; AC-XT: docetaxel 75mg/M2 IV with capecitabine 825mg/M2 PO BID 14/7 days every 21days for 4 cycles. The primary endpoint, improvement in disease-free survival (DFS) at 5 years, was not met (HR=0.84, p=0.12) likely due to lower-than-expected event rate. The secondary endpoint, overall survival (OS), was improved with capecitabine (HR 0.68, p=0.01) (O’Shaughnessy, J. ASCO, 2011). Methods: Molecular analyses demonstrate that pleomorphic lobular (mixed lobular/ductal) carcinomas evolve from the same precursor and/or through the same genetic pathway as classical lobular cancers (Reis-Filho, J., J Path, 2005). We conducted exploratory analyses to evaluate the addition of adjuvant capecitabine in ductal vs lobular or lobular/ductal (mixed) EBC within USON 01062. Histology was classified according to local pathology as...