Drug resistance and cancer chemotherapy strategy in breast cancer.

Evidence exists that spontaneous mutations to drug resistance are a major obstacle to chemotherapeutic cure in both experimental and clinical neoplasms. Analysis of this phenomenon indicates that certain treatment strategies may be more effective in circumventing resistance. Initiation of adjuvant chemotherapy at the earliest time feasible is such an approach. The use of combinations of non-cross resistant agents is another. These methods should reduce the probability that drug-resistant cells will be present at the time treatment is started, and in theory should produce improved therapeutic results.