Non-size-based response criteria to preoperative chemotherapy in patients with colorectal liver metastases: The morphologic response criteria

Since the introduction of biological agents, accumulating results have suggested that conventional size-based RECIST criteria do not enable accurate assessment of response to therapy, and that non-size-based changes in tumor morphology can be a surrogate marker for assessment of chemotherapeutic effect. The morphological response criteria are recently introduced, non-size-based criteria for patients undergoing chemotherapy for colorectal liver metastases (CLM). These novel criteria predict pathologic response and long-term survival of patients treated with preoperative chemotherapy, with or without bevacizumab, irrespective of their RECIST response. They have been validated in patients with resectable and unresectable CLM. These criteria are difficult to apply for small metastases and can be used as an adjunct to RECIST in assessment of response to preoperative chemotherapy.