Lapatinib Approved for Initial Treatment of Metastatic Breast Cancer

The U.S. Food and Drug Administration (FDA) has expanded its approval of lapatinib (TykerbR) to include initial treatment of metastatic, postmenopausal breast cancer that is both HER2-positive and hormone receptor-positive. In this setting, lapatinib is approved for use in combination with the aromatase inhibitor drug letrozole (FemaraR).

Twenty to thirty percent of breast cancers overexpress (make too much of) a protein known as HER2. Overexpression of this protein leads to increased growth of cancer cells. Fortunately, the development of treatments that specifically target HER2-positive cells has improved outcomes among women with HER2-positive breast cancer. Drugs that target HER2 include trastuzumab (HerceptinR) and lapatinib.

Lapatinib was initially approved in 2007 for use in combination with the chemotherapy drug capecitabine (XelodaR) for the treatment of HER2-positive advanced or metastatic breast cancer that has progressed following prior therapy with an anthracycline, a taxane, and trastuzumab.

The expansion of lapatinib’s approval to include the initial treatment of metastatic breast cancer was based on a study in 219 postmenopausal women with HER2-positive, hormone receptor-positive, metastatic breast cancer. Women were treated with either letrozole alone or letrozole plus lapatinib. Both drugs are given orally.

Progression-free survival was 5.2 months longer among women treated with letrozole and lapatinib than among women treated with letrozole alone.

The most common side effects of lapatinib include diarrhea, rash, nausea, and fatigue.

Reference: FDA News Release. FDA expands use of approved breast cancer drug. Available at: http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm199374.htm. Accessed February 1, 2010.

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