Significance of histopathological evaluation in primary therapy for breast cancer--recent trends in primary modality with pathological complete response (pCR) as endpoint.

In recent years, primary therapy has been used to improve the prognosis of patients with locally advanced breast cancer and to expand the indication for breast conserving treatment for patients with a relatively early stage of breast cancer. In addition, the therapeutic efficacy of primary therapy has been evaluated on the basis of pathological findings and pathological complete response (pCR)is considered to be a main target of primary therapy. The results of NSABP protocol B-18 and B-27, and the Aberdeen trials confirmed the prognostic significance of pCR in primary therapy and indicated the significance of minute pathological assessment. However, the criteria of pathological response is not yet universal, but the evaluation of the main invasive tumor, intraductal component and the regional lymph nodes, is thought to be necessary, shown by the "Histopathological Criteria for Assessment of Therapeutic Response in Breast Cancer" compiled by the Japanese Breast Cancer Society. Among these criteria, there exist methodological variations as to the evaluation of residual disease of intraductal carcinoma, thus some controversies exist. The presence of intraductal component might be negligible with regard to prognosis, but might be an important risk factor for local recurrence after breast conserving therapy. In the future, participation by the pathologist in the field of primary therapy for breast cancer will be a matter of course in most clinical studies.