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By Rebecca V. Snowden

Women with HER2+ inflammatory breast cancer who haven't responded to other cancer treatments may benefit from lapatinib (Tykerb), according to results from a phase II study published this month in The Lancet Oncology.

Inflammatory breast cancer (IBC) is a rare and aggressive type of breast cancer that accounts for about 1% to 3% of all breast cancers diagnosed in the United States. It's more likely to grow quickly and to have spread to nearby lymph nodes by the time it is diagnosed than other types of breast cancer, and the prognosis (outlook) is generally not as good. It isn't typically associated with a breast lump, which makes it difficult to diagnose early. Symptoms may include breast swelling; itching; a pink, red, or colored area, sometimes with a texture like the skin of an orange; and the breast feeling warm to the touch.

Patients with inflammatory breast cancer often have too much of a protein called human epidermal growth factor receptor-2 (HER2), which promotes the growth of cancer cells. Those patients are typically treated with a combination of chemotherapy drugs, trastuzumab (Herceptin), and radiation. If the cancer doesn't respond to those treatments, HER2+ inflammatory breast cancer patients don't have many other options.

This study looked at lapatinib's effect on 126 women with HER2+ inflammatory breast cancer who were previously treated with some combination of chemotherapy, Herceptin, or radiation, as well as 15 women who did not have HER2+ IBC. It was funded by GlaxoSmithKline (the maker of lapatinib) and led by researchers from several institutions, including the Chaim Sheba Medical Center, Sunnybrook in Toronto, and Duke University Medical Center.

The researchers found that 39% of the 126 women responded to the drug -- 1500 mg by mouth each day -- and of that group, the median overall survival was 18.4 months, compared to 8.4 months for patients who didn't respond. More than half of the women who had a response to the drug saw results within 2 months.

Patients who responded to the drug went an average of 25 weeks before the cancer started growing again. And at 6 months, 22% of HER2+ patients were still progression-free. Patients who previously responded to trastuzumab and responded to lapatinib had the longest median overall survival, followed by those who responded without prior trastuzumab treatment. None of the patients saw their disease disappear, although one patient saw her skin improve markedly.

Of the whole group of 141 women, common side effects – reported by at least 10% or more of the patients – included diarrhea, rash, fatigue, nausea, anorexia, shortness of breath, vomiting, and back pain. Diarrhea was the most common. Forty-five of the 141 women experienced some serious side effects – shortness of breath, fluid accumulation around the lungs, and fever – but these were not thought to be related to treatment with lapatinib in most cases. Five women died from side effects that may have been related to treatment with lapatinib.

While the study results are promising, the drug is not yet FDA-approved for this use. Lapatinib is also being studied for use against cancers of the prostate, brain, liver, and ovaries, as well as other cancers.

For more information about lapatinib, see our Drug Guide. For more information about this type of breast cancer, see Inflammatory Breast Cancer.

Reviewed by: Members of the ACS Medical Content Staff

Citation: "Lapatinib monotherapy in patients with HER2-overexpressing relapsed or refractory inflammatory breast cancer: final results and survival of the expanded HER2+ cohort in EGF103009, a phase II study." Published in the June 2009 issue of The Lancet Oncology. First author: Bella Kaufman, MD, The Chaim Sheba Medical Center, Tel Hashomer, Israel.