During surgery, the surgeon and radiation oncologist can use the information gained from intraoperative frozen-section analysis to make more informed decisions about the extent of the margins they have removed. Intraoperative re-resection of positive margins to achieve negative margins is routinely performed for patients with locally recurrent rectal cancer undergoing surgery and intraoperative radiation therapy. The purpose of this research was to determine if the re-resection of positive margins discovered during intraoperative frozen-section analysis results in better oncological outcomes. This is a cohort study with a retrospective design. This research looked at data from a large, prospectively collected, multicenter database. Included in this study were all patients who underwent surgical resection for locally recurrent rectal cancer with intraoperative radiation therapy between 2000 and 2015. The outcomes of the initial R0 resection, the initial R1 converted to R0 after re-resection, and the initial R1 remaining R1 after re-resection were compared. The R2 group did not include resections with grossly positive margins. The primary endpoints were 5-year overall survival, recurrence-free survival, and local recurrence. A total of 267 patients were analyzed (n = 94 for initial R0 resection; n = 95 for initial R1 that became R0 after re-resection; n = 78 for initial R1 that remained R1). Overall survival ranged from 4.4 years for those with an initial resection of R0 to 2.7 years for those whose initial R1 was converted to R0 after re-resection and 2.9 years for those whose initial R1 remained R1 after re-resection (P=0.01). Initial R0 resection had a recurrence-free survival rate of 3.0 years, while initial R1 that was converted to R0 after re-resection and initial R1 that remained R1 after re-resection both had recurrences within 1.8 years (P≤0.01). Patients with R1 or R1 with re-resection had a similar overall survival rate to those with R0 or R0 (P=0.62). Surviving without a recurrence and not having a local recurrence was the same for both groups. The study was restricted to patients undergoing intraoperative radiation therapy, which resulted in a less representative sample of the general population. In patients with locally recurrent rectal cancer undergoing surgery and intraoperative radiation therapy, re-resection of microscopically positive margins to obtain R0 status does not appear to provide a significant survival advantage or prevent local re-recurrence.
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