Chemotherapy has also an effect on primary tumor in colon carcinoma

This study characterizes the histological effect of chemotherapy (CT) on primary colonic tumors.

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.

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.

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.