Histologic evaluation of intrahepatic micrometastases in patients treated with or without neoadjuvant chemotherapy for colorectal carcinoma liver metastasis.

In the present retrospective study, we tested the hypothesis that neoadjuvant chemotherapy (NAC) as a treatment for patients with colorectal carcinoma liver metastases (CRLM) may reduce intrahepatic micrometastases. The incidence and distribution of intrahepatic micrometastases were determined in specimens resected from 63 patients who underwent hepatectomy for CRLM (21 treated with NAC and 42 without). In addition, the therapeutic efficacy of NAC was evaluated histologically. Intrahepatic micrometastases were defined as microscopic lesions spatially separated from the gross tumor. The distance from these lesions to the border of the hepatic tumor was measured on histological specimens and the density of intrahepatic micrometastases (number of lesions/mm(2)) was determined in regions close to (<1 cm) the gross hepatic tumor. Of the 21 patients treated with NAC, 13 were identified as having a partial response according to the Response Evaluation Criteria in Solid Tumors (RECIST) guidelines; thus, the overall response rate was 62%. Histologic evaluation of the therapeutic efficacy of NAC was significantly associated with tumor response to NAC according to the RECIST guidelines (p=0.048). In all, 260 intrahepatic micrometastases were detected in 39 patients (62%). Intrahepatic micrometastases were less frequently detected in NAC-treated patients than in untreated patients (5/21 [24%] vs. 34/42 [81%], respectively; p<0.001). There were no significant differences in the distance and density of intrahepatic micrometastases between the two groups (p=0.313 and p=0.526, respectively). In conclusion, NAC reduces the incidence of intrahepatic micrometastases in patients with CRLM, but NAC has no significant effect on their distribution when intrahepatic micrometastases are present.