Baselga stressed that the study looked only at women with early-stage HER2-positive breast cancers, and that the drug Tykerb is approved now only for advanced breast cancers.
The study is well done and important, said Dr. Len Lichtenfeld, deputy chief medical officer for the American Cancer Society. The two drugs, he said, "affect the same pathway but do it in a different way."
While the combination showed a better response rate, "there is also an increased level of side effects," he noted.
While no major heart problems occurred, those on Tykerb alone or the two-drug combination had more diarrhea. Liver-enzyme alterations were also more frequent when Tykerb was used.
GlaxoSmithKline notes that liver toxicity with the drug may be severe and that deaths have been reported, although the cause of the deaths has not been determined.
The important question, however, has not been answered yet, Lichtenfeld said. That's the effect on overall survival in using the two-drug approach. The researchers are continuing to evaluate that.
In another study, published online Jan. 17 in The Lancet Oncology, researchers from Germany reported that Tykerb is less beneficial than Herceptin as a single-drug therapy.
They assigned 620 women with HER2-positive breast cancer to get standard chemotherapy plus Herceptin or Tykerb.
They looked to see which drug was better at eliminating invasive cancer in the breast and metastatic cells in the lymph nodes. While 30 percent of those in the Herceptin group had this response, 23 percent of the Tykerb group did. The study was funded by drug makers GlaxoSmithKline, Roche and Sanofi-Aventis.
Baselga reports receiving honoraria from Roche; other co-authors report receiving speaking fees or honoraria from GlaxoSmithKline and fees from other drug companies.
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