Full-thickness scar resection following R1/Rx excised T1 colorectal cancers as alternative to completion surgery.

Local full-thickness resections of the scar (FTRS) following local excision of a T1 CRC with uncertain resection margins is proposed as alternative strategy to completion surgery (CS), provided that no local intramural residual cancer (LIRC) is found. However, a comparison on long-term oncological outcome between both strategies is missing.A large cohort of consecutive T1 CRCs between 2000 and 2017 was used. Patients were selected if they had a macroscopically complete local excision of a T1 CRC but positive or unassessable (R1/Rx) resection margins at histology, and without lymphovascular invasion or poor differentiation. Patients treated with CS or FTSR were compared on the presence of CRC recurrence, 5-year overall (OS), disease-free (DFS) and metastasis-free survival (MFS).Of 3697 patients with a T1 CRC, 434 met the inclusion criteria (mean age 66 years, 61% male). 334 patients underwent CS and 100 FTRS. Median follow-up was 64 months. CRC recurrence was seen in 7 patients with CS (2.2%, 95%CI 0.9 - 4.6%) and 8 patients with FTRS (9.0%, 95% CI 3.9 - 17.7%). DFS was lower in FTRS strategy (96.8% vs 89.9%, p=0.019), but 5/8 FTRS recurrences could be treated with salvage surgery. The MFS (CS 96.8% vs FTRS 92.1%, p=0.10) and OS (CS 95.6% vs FTRS 94.4%, p=0.55) did not differ significantly between both strategies.FTRS after local excision of a T1 CRC with R1/Rx resection margins as sole risk factor, followed by surveillance and salvage surgery in case of CRC recurrence, could be a valid alternative strategy to CS.