Background: We analyzed the treatment outcomes after curative surgery for stage IV colorectal cancer to develop outcome-based follow-up protocols and treatment strategies. Methods: This study was a multi-institutional retrospective analysis of treatment outcomes in patients who underwent R0 surgery for stage IV colorectal cancer. Results: A total of 1133 patients, of whom 837 had recurrence, were included in this study. Recurrence occurred within 12 and 24 months after R0 surgery in 452 (54.0 %) and 652 (77.9 %) patients, respectively. Surgical resection was performed less frequently for recurrence within 12 months of R0 surgery than for recurrence after more than 12 months (p = 0.003). Prognosis was significantly better in patients who had recurrence more than 24 months after R0 surgery than in those who had recurrence within 24 months; this was not only for all patients but also specifically for patients with resection for recurrent disease. Recurrence was less frequent in patients who received preoperative chemotherapy than in patients who did not receive preoperative chemotherapy (p = 0.04). Of significance, fewer patients who received preoperative chemotherapy (57.5 %) had recurrence within 24 months compared with patients who did not receive preoperative chemotherapy (79.8 %) (p = 0.00001). Conclusions: Intensive follow-up for at least 24 months was considered appropriate for monitoring disease recurrence after R0 surgery for stage IV colorectal cancer. In addition, preoperative chemotherapy contributed to improved outcomes.
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