Morphological response and tumor shrinkage as predictive factors in metastatic colorectal cancer treated with first-line capecitabine, oxaliplatin, and bevacizumab

Purpose: Morphologic response (MR) is a novel predictor of chemotherapeutic efficacy in solid tumors, especially those treated with anti-vascular endothelial growth factor (VEGF) antibodies. Nevertheless, the importance of MR in systemic chemotherapy for colorectal liver metastases (CLM) remains unclear. This study aimed to evaluate the usefulness of MR as a factor associated with the therapeutic effects of chemotherapy plus bevacizumab for initially unresectable CLM. Methods: We retrospectively evaluated the associations among MR and/or Response Evaluation Criteria in Solid Tumors(RECIST), progression-free survival (PFS), and overall survival (OS) in patients who received first-line capecitabine, oxaliplatin, and bevacizumab treatment for initially unresectable CLM using multivariate analysis. Patients who showed a complete or partial response based on the RECIST, or an optimal response based on MR, were defined as “responders.” Results: A total of 92 patients were examined, including 31 (33%) patients who showed an optimal response. PFS and OS estimates were comparable in MR responders and non-responders (13.6 vs 11.6 months, p=0.47; 26.6 vs 24.6 months, p=0.21, respectively). RECIST responders showed better PFS and OS than non-responders (14.8 vs 8.6 months, p<0.01; 30.7 vs 17.8 months, p<0.01, respectively). The median PFS and OS estimates of MR and RECIST responders were better than those of single responders or non-responders (p<0.01). Histological type and RECIST response were independently associated with PFS and OS. Conclusion: MR predicts neither PFS nor OS; nevertheless, it may be useful when combined with the RECIST. Approval by the Ethics Committee of The Cancer Institute Hospital of JFCR in 2017 (No. 2017-GA-1123): retrospectively registered