Purpose: Despite marked recent advances in chemotherapy, few reports have focused on the prognosis for patients with metastatic colorectal cancer (mCRC) achieving complete response (CR) after systemic chemotherapy. This study investigated the clinical course of mCRC patients achieving CR and evaluated the role of CR in chemotherapy.Methods: This retrospective study searched a prospectively maintained database at the author's institute to identify medical records for mCRC patients achieving CR

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... ter systematic chemotherapy from January 2007 to March 2020.Results: The search yielded 23 patients with confirmed CR to systemic chemotherapy. Median time to CR from treatment initiation was 6.8 months. Maintenance chemotherapy was continued for 22 of 23 patients. Median duration of maintenance chemotherapy was 11.1 months. Disease progression occurred for 17 (73.9%) patients at a median 48.1-month follow-up. Median progression-free survival was 26.6 months. Median overall survival was 91.7 months.Conclusions: Patients with CR to chemotherapy had a high probability of disease progression, but a relatively long-term prognosis. Treatment strategies after achievement of CR should be based an understanding of the high potential that tumor cells will remain. Use of maintenance chemotherapy after achievement of CR is still unclear, the recent data do not demonstrate a negative impact for continuing maintenance chemotherapy after CR.