Pathological Response Criteria

Histopathological examination is an essential component of multidisciplinary care of patients who undergo surgical resection of colorectal liver metastases (CLM). The examination entails macroscopic and microscopic evaluations that provide predictive and prognostic information. This includes the response to preoperative medical therapy, completeness of resection, and effects of preoperative therapy on the nonneoplastic liver. The extent of residual carcinoma is assessed quantitatively by estimating the proportion of residual cancer cells in relation to the total tumor area. The response is classified into the three semi-quantitative subsets: complete response, no residual cancer cells; major response, 1–49% residual cancer cells remaining; minor response, 50% or more residual cancer cells remaining. Survival after CLM resection was significantly better in patients with complete response and major response than in patients with minor response. Pathology changes after preoperative chemotherapy in patients undergoing CLM resection predict survival outcome and contribute to a better understanding of the biology of CLM.