(CHICAGO, IL) – Trastuzumab-naïve metastatic breast cancer patients have significantly higher clinical benefit rates and longer overall survival (OS) times when treated with HER2-targeted therapies, compared with patients who previously received adjuvant trastuzumab, according to a study reported at the 2012 American Society of Clinical Oncology Annual Meeting.

Although trastuzumab (Herceptin) was first approved in 2006 for adjuvant therapy in women with early-stage, HER2+ breast cancer, there is limited data regarding outcomes for these same patients who go on to receive trastuzumab or lapatinib for metastatic breast cancer, said lead study author Rashmi Krishna Murthy, MD, University of Texas MD Anderson Cancer Center, Houston, TX.

To address that gap, Dr. Murphy’s team analyzed data from 347 patients with HER2+ breast cancer who received first-line trastuzumab or lapatinib treatment for metastatic disease between 1997 and 2011; 72 patients had received adjuvant trastuzumab and 275 had not. The HER2+ status of the patients was confirmed by immunohistochemistry scores of 3 or higher, or fluorescence in situ hybridization (HER2/CEP17 ratio ≥ 2).                           

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Trastuzumab-naïve patients saw better complete or partial response rates compared with patients who had previously received adjuvant trastuzumab therapy (48% vs 32%) but the difference was not statistically significant (P=0.11).The clinical benefit rate (complete or partial responses, and stable disease for 6 months) was significantly higher for trastuzumab-naïve arm patients (68% vs 42%; adjusted odds ratio = 0.4; P=0.025).

Dr. Murthy and colleagues said these findings highlight the importance of recognizing a pre-treated population and calls for further research in this area.