Patterns of failure in rectal cancer with positive circumferential resection margin after surgery following preoperative chemoradiation: A propensity core matching analysis.

Objective: To compare the patterns of failure between rectal cancer patients with negative and positive circumferential resection margin (CRM) after surgery following preoperative chemoradiation. Methods: Of 944 stage II-III rectal cancer patients treated with radical surgery following preoperative chemoradiation, 74 patients (7.8%) showed positive CRM. Each 72 patients from negative and positive CRM groups were identified by propensity score matching and compared in terms of survival outcomes and patterns of failure. Local failure was defined as recurrence at the anastomosis site or adjacent to the mesorectal fascia. Results: The median follow-up was 46 months (range, 4-155). No difference was observed in 5-year local recurrence-free survival (93.4% vs 89.6%, p = 0.442) in the negative and positive CRM groups. There was statistically significant difference in relapse-free survival (57.1% vs 39.1%, p = 0.042). Negative CRM group showed favorable outcomes than positive CRM in distant metastasis-free survival (59.4% vs 43.3%, p = 0.069) and overall survival (67.5% vs 55.8%, p = 0.186), but the difference was not statistically significant. As the initial failure pattern, there were 30 and 43 recurrences in the negative and positive CRM groups (local 6.6 and 7.3%, regional 12.8 and 14.4%, and distant 38.5 and 54.9%). Isolated local recurrence was identified in two with negative CRM and in none with positive CRM (p = 0.497). Conclusion: Distant metastasis was the major pattern of failure regardless of CRM involvement in rectal cancer patients treated with surgery following preoperative chemoradiation. It would be taken account of our finding on adjuvant treatment for the patient with positive CRM. Advances in knowledge: Investigation of the patterns of failure in patients with CRM involvement after preoperative chemoradiation followed by surgery can be conducive to selecting the appropriate approach to additional treatment for them.