Evaluation of the necessity of primary tumor resection for synchronous metastatic colorectal cancer

We evaluated the need for primary tumor resection in patients with colorectal cancer (CRC) and synchronous unresectable metastases who underwent chemotherapy, and identified the associations between the primary tumor characteristics and risk of intestinal obstruction or perforation. We retrospectively analyzed the survival and complication rates of patients with synchronous metastatic CRC treated between April 2005 and December 2011. Of 131 patients, 68 underwent primary tumor resection before chemotherapy, and 63 were treated without resection before chemotherapy. The overall survival (OS) did not significantly differ between the two groups (log-rank P = 0.53). In the resection group, 12 patients (17.6 %) developed postoperative complications. In the non-resection group, 16 patients (25.4 %) required surgical intervention owing to obstruction or perforation during their treatment. Surgical intervention did not affect the OS. A circumferential tumor was a risk factor for obstruction or perforation of the colorectum in non-resected patients (odds ratio = 11.163; P = 0.006). Resection of primary tumors before chemotherapy is unnecessary in selected patients with synchronous metastatic colorectal cancer. A circumferential tumor is a risk factor for obstruction or perforation during chemotherapy in cases without primary tumor resection.