The Preclinical Scientific Basis for Adjuvant Chemotherapy in Breast Cancer

The relatively slow and limited regression of solid tumor masses following and during chemotherapy initially led many to believe, because of the long duration of treatment implied to be necessary by these slow regressions, that chemotherapeutic cure of a solid tumor was impractical if not impossible. However, with the later realization that solid tumor mass reduction grossly underestimates the fraction of a tumor cell population killed by chemotherapy [6], it became evident that chemotherapy may be more effective than had been anticipated. Furthermore, it has been well documented that curability is inversely proportional to the size of the tumor cell population [4]. Thus, it was anticipated that tumor debulking followed by chemotherapy, aimed at destruction of surviving tumor stem cells, would lead to cure for a significant fraction of appropriately staged breast cancer patients. The first clinical trials, however, were disappointing [3].