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.