Endoscopic evaluation of primary tumor response in patients with metastatic colorectal cancer treated by systemic chemotherapy.

Background: The number of cases of metastatic colorectal cancer treated by chemotherapy without primary tumor resection has recently increased. However, evaluation of primary tumor response by computed tomography is difficult in such cases. In this study, the usefulness of evaluation of primary tumor response to chemotherapy by endoscopy was investigated.
Methods: This retrospective analysis was performed at the Shizuoka Cancer Center and included 31 patients (88 evaluations) with metastatic colorectal cancer. Computed tomography and endoscopy were performed concomitantly between September 2002 and June 2006. Patients were treated by systemic chemotherapy without prophylactic primary tumor resection. Definitions of primary tumor response were as follows: (1) complete response, confirmed by colorectal biopsy; (2) progressive disease, enlargement of at least one of five tumor parameters; and (3) neither (1) nor (2). Computed tomography was performed to evaluate primary tumor response according to the Response Evaluation Criteria in Solid Tumors and to identify colorectal stenosis secondary to primary tumors.
Results: The rate of concordance between endoscopy and computed tomography for evaluation of primary tumor response was 75%. Colorectal stenosis was detected 14 times by endoscopy (9 cases) and 3 times by computed tomography (3 cases). Of the 7 patients in whom surgery was required, 6 exhibited stenotic symptoms before endoscopic detection.
Conclusions: With regard to primary tumor response evaluation, a high concordance rate was observed between endoscopy and computed tomography, although endoscopic evaluation appeared more sensitive in detecting colorectal stenosis requiring surgical treatment.