The biology of neoadjuvant chemotherapy for breast cancer.

Neoadjuvant/pre-surgical medical therapy of breast cancer provides a unique opportunity to derive biological information related to tumour response. Large clinical trials of neoadjuvant chemotherapy have established that pathological complete remission is an independent predictor of improved disease-free survival. Clinical response has been found to parallel substantial reductions in the proliferation of breast cancer cells. Increased apoptosis also occurs, but it is not closely associated with response. Numerous biological markers such as p53, bcl-2, oestrogen receptor (ER) and HER2 have been assessed for their possible role in chemoresistance/response, but the data are not clear at this stage. Continuing work using cDNA microarrays may yield new, more reliable indices of likely response and an improved insight into biological processes related to chemotherapeutic response.