Outcome of Mismatch Repair‐Deficient Metastatic Colorectal Cancer: The Mayo Clinic Experience

AbstractBackground.Deficiencies in the DNA mismatch repair system cause errors during DNA replication, which in turn give rise to microsatellite instability (MSI). The impact of MSI on survival in metastatic colorectal cancer (mCRC) is unclear. This cohort study aims to investigate the prognostic and predictive value of MSI in mCRC prior to the immune therapy era.Materials and Methods.A total of 75 MSI‐high (MSI‐H) mCRC patients (pts) and 75 matched (age, gender, disease sidedness, metachronous/synchronous) microsatellite‐stable (MSS) mCRC pts were identified from 1,268 mCRC pts who had MSI/mismatch repair test results at Mayo Clinic Rochester between January 1992 and July 2016. A retrospective review was conducted by using data from electronic medical records. Statistical analyses utilized the Kaplan‐Meier method, log‐rank test, and Cox proportional hazards models.Results.The MSS group was well matched to the MSI‐H group based on age, gender, location, and chronicity of metastatic disease. MSI‐H mCRC pts had earlier disease recurrence (median time from initial diagnosis to metastatic disease diagnosis, MSI‐H group 12.9 vs. MSS group 20.9 months, p = .034). Median overall survival (OS) was 28.1 and 37.4 months for MSI‐H and MSS pts, respectively (p = .99). In total, 94.7% of MSI‐H pts and 98.7% of MSS pts had fluoropyrimidine‐based chemotherapy for metastatic disease, and there was no difference in OS between these two groups (32.3 vs. 37.4 month...
Source: The Oncologist - Category: Cancer & Oncology Authors: Tags: Gastrointestinal Cancer Source Type: research