In patients with human epidermal growth factor receptor (HER2)–positive advanced breast cancer, the combination of Herceptin® (trastuzumab) plus a taxane resulted in delayed time to cancer progression and was associated with fewer side effects than Tykerb® (lapatinib) plus a taxane, according to final clinical trial results reported in the Journal of Clinical Oncology.

The HER2 pathway is a biological pathway involved in cellular replication and growth. Approximately 20-25% of breast cancers overexpress the HER2 protein and are referred to as HER2-positive. Herceptin and Tykerb both target and block the HER2-protein, and are used for the treatment of both early-stage and more advanced HER2-positive breast cancer.

The NCIC Clinical Trials Group enrolled and evaluated 537 patients in 21 countries with centrally confirmed HER2-postive advanced breast cancer that were treated with a taxane plus Tykerb or Herceptin. These individuals have now been followed a median of 21.5 months.

The investigators reported that patients taking Tykerb plus a taxane experienced a median progression-free survival of 9.0 months compared to 11.3 months for those taking Herceptin plus a taxane. More importantly, patients with centrally confirmed HER2-positive disease receiving Tykerb had a worse overall survival.

Treatment discontinuation because of side effects also favored Herceptin and was more frequent with Tykerb (15%) than Herceptin (8%). Significant diarrhea occurred in 19% versus 1% of the Tykerb and Herceptin treated patients respectively, and rashes occurred in 8% of patients treated with Tykerb compared to 0% of those treated with Herceptin.

The authors noted that these results “have implications for the treatment of patients with advanced HER2-positive breast cancer, where dual therapy or newer agents are not available but where the older agents or biosimilars may be available and affordable.”

Reference: Gelmon K, Boyle F, Kaufman B, et al. Lapatinib or Trastuzumab Plus Taxane Therapy for Human Epidermal Growth Factor Receptor 2–Positive Advanced Breast Cancer: Final Results of NCIC CTG MA.31. J. Clin. Oncol. 2015 Mar. 16 doi:10.1200/JCO.2014.56.9590

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