(HealthDay News) – Treatment of human epidermal growth factor receptor 2 (HER2)-positive breast cancer with two anti-HER2 agents (lapatinib and trastuzumab) is superior to treatment with single-agent therapy, according to a study published online January 17 in The Lancet.

José Baselga, MD, from Harvard Medical School in Boston, MA, and colleagues randomly assigned 455 women with HER2-positive primary breast cancer, with tumors larger than 2cm diameter, to receive intravenous trastuzumab, oral lapatinib, or both for six weeks. A weekly dose of paclitaxel was added for a further 12 weeks, followed by surgical removal of the tumor. The rate of pathologic complete response (pCR) was the primary end point.

The researchers found that the rate of pCR was 51.3% for patients receiving lapatinib and trastuzumab, compared with 29.5 and 24.7% in patients receiving trastuzumab and lapatinib alone, respectively. There was no significant difference between lapatinib and trastuzumab groups with respect to pCR. There were no major cardiac dysfunctions, but grade 3 diarrhea and liver-enzyme alterations were more frequent with lapatinib and lapatinib plus trastuzumab treatment than with trastuzumab alone.

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“In conclusion, this open-label, multicenter, phase 3 study showed that dual inhibition of HER2 with lapatinib and trastuzumab in combination with paclitaxel is better than single-agent HER2 targeting,” the authors write.

Several authors disclosed financial ties with pharmaceutical companies, including GlaxoSmithKline, which funded the study.

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