ATLANTA--In laboratory models, the "highest possible doses of chemotherapy" and a combination of agents are necessary to achieve curative therapy in breast cancer, Karen H. Antman, MD, said at the American Society of Clinical Oncology's (ASCO) Educational Conference. But when treating breast cancer with drugs that damage stem cells, "you may not be able to give even one dose without stem cell support," she said.
Breast cancer is an ideal tumor in which to study high-dose chemotherapy, based on its sensitivity at conventional doses, said Dr. Antman, professor of medicine and chief of the Division of Medical Oncology, Columbia University College of Physicians and Surgeons.
In the laboratory, resistance to alkylating agents can often be overcome by using a five- to 10-fold higher dose. Clinically, a one- or twofold increase has produced mixed results, she said.
For patients with previously untreated or responding metastatic breast cancer, investigators have used several approaches to high-dose therapy, including an induction regimen that reduces tumor size and may also decrease the number of resistant cells, she said. Sequential trials are underway at several centers to find the best induction regimen before proceeding to randomized trials.
Breast Cancer and ABMT
In reviewing data collected by the North American Autologous Bone Marrow Transplant Registry, Dr. Antman noted that high-dose chemotherapy with stem cell support has become an increasingly used procedure for breast cancer and that, since 1991, breast cancer has been the most common diagnosis for autologous transplantation.
Transplant procedures for breast cancer have increased fivefold since 1989 when 261 transplants were reported to the registry. That number was almost 1,000 in 1992, and for the first 9 months of 1993, was already up to 812, she said.