Prognostic value of mismatch repair deficiency in patients receiving first-line fluoropyrimidine plus platinum for metastatic, recurrent, or unresectable gastric cancer

We examined the impact of mismatch repair (MMR) status on efficacy of first-line fluoropyrimidine plus platinum (FP) chemotherapy in patients with HER2-negative metastatic, recurrent, or unresectable gastric cancer (mGC). Patients with mGC receiving first-line FP between 2015 and 2018 at Asan Medical Center, Korea, were reviewed. We evaluated the clinical characteristics and the efficacy of chemotherapy according to MMR status in patients with available immunohistochemistry results. Of 895 patients, we analyzed 543 with available MMR protein expression results, and deficient MMR (dMMR) was detected in 4.4