Wyeth ( WYE) has decided to stop late-stage trials of a proposed breast cancer treatment after a review concluded that the combination therapy being tested probably wouldn't be more effective than one of the drugs on its own. The phase III trial involved the experimental drug temsirolimus plus the already-approved breast cancer drug Femara. The combination was being tested as a primary treatment for postmenopausal women with a specific type of breast cancer that has spread to other parts of the body, called hormone-receptor positive metastatic breast cancer. Phase III is the stage of studies conducted just before a drug is submitted for Food and Drug Administration approval. According to an independent data monitoring committee, the trial was unlikely to reach the desired efficacy outcome needed to prove that the combination treatment was more effective than using Femara alone. "While not the anticipated outcome, it is unfortunately not unusual for cancer drugs to work in some tumor types and not others, or even work in only some specific subpopulations of cancer patients," said Dr. Gary Stiles, Wyeth's chief medical officer, in a press release on Thursday. "We remain committed to studying temsirolimus in other cancer indications." The breast cancer trial involved a form of the drug taken by mouth. Two other phase III studies, on an intravenous version of the drug for kidney cancer and a type of blood cancer called mantle-cell lymphoma, are continuing. Wyeth's shares were up 35 cents to $49.70.