Background: This study characterizes the histological effect of chemotherapy (CT) on primary colonic tumors.
Methods: Between 2000 and 2006, 38 patients with stage IV colon cancer underwent resection of the primary, after chemotherapy (CT group, n = 16) or without preoperative CT (control group, n = 22). For all primary tumors, histological analysis included: fibrosis, acellular necrosis, acellular mucin pools, lymphoplasmacytic infiltration, and changes at tumor surface. Tumor regression grade (TRG) was determined by the amount of residual tumor cells and was graded from 1 to 5.
Results: No patient had complete histological response. Major histological tumor regression (TRG2) was observed in 70% of patients treated by CT and none of the not treated patients (P < 0.0001). Fibrosis, acellular necrosis, and surface changes were significantly increased in the CT group. TRG in the primary was comparable to the TRG in the corresponding liver metastases for 7/9 patients who underwent both colonic and hepatic resection after CT.
Conclusion: CT induces major histological response in 70% of colon cancers. Response to CT in the primary and the corresponding liver metastases are correlated. These results support a policy of initial CT management for stage IV colon cancer and may warrant future studies of neoadjuvant CT in locally advanced colon carcinomas.