Practice Patterns and Trends in the Surgical Management of Mismatch Repair Deficient Colon Cancer.

Introduction: Defects in the DNA mismatch repair (MMR) pathway can predispose individuals to colorectal cancer (CRC), with germline mutations in this pathway leading to Lynch syndrome. Consequently, universal MMR testing is recommended for all newly diagnosed CRC patients to detect mismatch repair deficient (MMR-D) tumors, enabling informed treatment decisions. Given the increased potential for metachronous disease in patients with Lynch syndrome, the current guidelines for surgical management of Lynch-associated colon cancer recommend extended resection in patients under age 60.

Methods: A retrospective analysis of nonmetastatic CRC was performed from the National Cancer Database to evaluate the current trends and practice patterns in the surgical management of MMR-D colon cancer, as well as assess the factors influencing choice of surgical procedure.

Results: From 2018 to 2020, 98,112 nonmetastatic CRC patients were identified, with 19.93% being MMR-D. MMR-D colon cancer patients were more likely to undergo extended resection than those with mismatch repair proficient tumors (9.4% versus 4.2%, P < 0.001). When accounting for approximately one-fourth of MMR-D colon cancers being attributable to Lynch syndrome, the frequency of extended resection was less than expected (9.4% versus 25%, P < 0.001). MMR-D patients under age 60 were more likely to undergo extended resection than those over age 60 (9% versus 3%) (odds ratio [OR] 3.57, 95% confidence interval [CI] 3.06-4.15). Several factors were associated with decreased rate of extended resection: uninsured (OR 0.42, 95% CI 0.21-0.84), Black race (OR 0.54, 95% CI 0.35-0.82), treatment at nonacademic centers (OR 0.74, 95% CI 0.56-0.97), and crowfly distance >25 miles (OR 1.98, 95% CI 1.14-3.45).

Conclusions: These findings provide valuable insight into the current surgical practice patterns in the management of MMR-D colon cancers and possibly colon cancers associated with Lynch syndrome.