Relationship between survival to breast cancer and level of HER2 expression by immunohistochemistry.

e13078Background: Central review of NSABP B-31 showed that some central-review HER2-negative patients benefited from trastuzumab, but survival according to different levels of HER2 expression by immunohistochemistry (IHC) is unknown. The aim of the present study was to examine the survival of trastuzumab-naive patients with breast cancer according to the level of HER2 expression by IHC. Methods: This was a retrospective study of all women who were treated for an invasive breast cancer at the Centre des maladies du Sein Deschenes-Fabia (Quebec City, Province of Quebec, Canada) between July 1999 and December 2010. Patients were grouped according to the HER2 status by IHC of their primary cancer (0 vs. 1+ vs. 2+ vs. 3+). Survival was obtained from the death registry of the Ministry of Health. Follow-up was censored on December 31st, 2012. Results: During the study period, 2571 patients with invasive breast cancer, with available HER2 status by IHC and survival data, and naive to anti-HER2 therapy were treate...