SECONDARY DRUG-RESISTANCE IN BREAST-CANCER - FAILURE TO REVERSE WITH ORAL NIFEDIPINE

We tested the efficacy of nifedipine to reverse acquired resistance to chemotherapy regimens containing doxorubicin or vinblastine or both i n 12 patients with metastatic breast cancer, Ail patients had been rec eiving one or both of these drugs, had had a prior partial response (m edian duration 5 months, range 2-10) and subsequently progressed. Imme diately after drug resistance was documented by tumor progression, eli gible patients with measurable or evaluable disease were treated with nifedipine beginning 3 days before restarting the same chemotherapy. T he initial dose of nifedipine was 20 mg TID, escalating daily to 40 mg TID on day 3 if the patient had no serious side effects, Nifedipine w as continued at the highest tolerable dose during and for 2 days after completion of the chemotherapy, Most patients had less than or equal to 2 prior chemotherapy regimens and a median Zubrod performance statu s of 1. Twelve patients received a total of 23 courses preceded by nif edipine. No objective tumor responses were observed, The expected toxi c effects attributable to nifedipine occurred, but nifedipine did not increase the toxicity caused by the chemotherapy, Nifedipine, given in this dose and schedule, did not reverse acquired drug resistance in p atients with breast cancer. (C) 1997 Wiley-Liss, Inc.