Mismatch repair status as a beneficial predictor of fluorouracil-based adjuvant chemotherapy for pancreatic cancer.

BACKGROUND: Prior studies have indicated that patients with colorectal cancer with deficient mismatch repair have particular clinicopathologic features that distinguish them from patients with tumors with proficient mismatch repair. However, the effect of the mismatch repair status on outcomes after adjuvant chemotherapy for pancreatic cancer is still unknown.

METHODS: Pancreatic cancer patients who underwent R0 resection between January 2013 and December 2015 at Fudan University Shanghai Cancer Center were included in this study. Mismatch repair status was determined by immunohistochemistry of mismatch repair proteins. Prognostic factors for deficient mismatch repair and proficient mismatch repair tumors were analyzed using Cox models.

RESULTS: In total, 442 of 590 patients met the inclusion criteria, and their mismatch repair status was determined; the study group consisted of 75 patients with deficient mismatch repair and 367 patients with proficient mismatch repair. Among the 147 patients who underwent surgery alone, patients with deficient mismatch repair tumors had a better overall survival than patients with proficient mismatch repair tumors (hazard ratio = 0.555 [95% confidence interval 0.331-0.931]; P = .026). Compared with patients who underwent surgery, 161 patients who received gemcitabine-based adjuvant chemotherapy had improvements in both disease-free survival and overall survival, regardless of mismatch repair status. However, 5-fluorouracil-based adjuvant chemotherapy yielded a favorable disease-free survival in the proficient mismatch repair group but conferred no survival advantage in the deficient mismatch repair group (hazard ratio = 0.930 [95% confidence interval 0.497-1.743]; P = .821).

CONCLUSION: Mismatch repair status in pancreatic cancer patients is not only a prognostic indicator but also a potential guiding factor for the use of 5-fluorouracil-based adjuvant chemotherapy.