Tamoxifen and Chemotherapy: Timing Matters
Key Words: breast cancer, chemotherapy, tamoxifen. (Definitions of many terms related to cancer can be found in the Cancer.gov Dictionary.)
A combination of chemotherapy and the hormone therapy tamoxifen (Nolvadex®) is more effective than tamoxifen alone in preventing the recurrence of breast cancer in some women after surgery, according to recent phase III clinical trial results presented on May 19, 2002. In addition, the trial results indicate that the combined treatment works better when tamoxifen is administered after chemotherapy has finished, rather than at the same time.
The study was chaired by Kathy Albain, M.D., of Loyola University Medical Center in Maywood, Ill., on behalf of the Southwest Oncology Group and the North American Breast Cancer Intergroup. She presented the results at the 2002 annual meeting of the American Society of Clinical Oncology in Orlando, Fla.
The combination of chemotherapy and tamoxifen is already recommended by many physicians for women whose cancer is the kind that depends on female hormones such as estrogen in order to grow. (Tamoxifen blocks the action of these hormones.) But until this study, there had been no research that would tell physicians whether it's best to give tamoxifen at the same time a patient receives chemotherapy (concurrently) or to wait until the chemotherapy regimen is complete.
The new findings "will likely change practice on the part of those who have followed" the concurrent model, said Jeffrey Abrams, M.D., of the National Cancer Institute's Cancer Therapy Evaluation Program, an opinion shared by the study's authors. About 100,000 women a year with high-risk, early stage breast cancer are given a treatment prescription of chemotherapy plus tamoxifen.
Albain and her colleagues in the U.S. and Canada studied 1,477 postmenopausal women with early-stage breast cancer that had not spread beyond the lymph nodes and whose tumors were responsive to estrogen or progesterone. The women were randomly assigned to one of three study groups. The first group of 361 received tamoxifen alone on a daily basis for five years. The second group of 566 received a chemotherapy regimen of cyclophosphamide, adriamycin, and 5-fluorouracil (CAF) plus tamoxifen for six months, and then completed five years of tamoxifen. And the third group of 550 received CAF alone for six months followed by five years of tamoxifen.
Researchers followed the women for an average of eight years and found that 67 percent of women who received CAF followed by tamoxifen were alive without a recurrence of their breast cancer, compared to 62 percent of the women receiving CAF and tamoxifen concurrently, and 55 percent who received tamoxifen alone.
Taken together, the study results showed that finishing chemotherapy before starting tamoxifen gave women an 18 percent advantage over those taking the therapies concurrently. The authors suggested that, when taken together, tamoxifen may cut the effectiveness of chemotherapy, perhaps by as much as 50 percent.
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