ANALYSIS OF DNA MISMATCH REPAIR SYSTEM STATUS IN COLORECTAL CANCER: AN EXPLORATORY CLINICAL-PATHOLOGICAL STUDY IN AN ARGENTINE COHORT

YONAMINE K; CURVALE C; SAENZ J; VOGEL E; MATANÓ R; TASSI V; SOBOL NT; SOLERNÓ LM; LLAVONA C; GOTTARDO MF; SEGATORI V; ALONSO DF, ; GARONA J

Mar del Plata

Congreso; REUNIÓN CONJUNTA SAIC SAI&FAIC SAFIS 2022; 2022

Sociedad Argentina de Investigación Clínica

In Argentina, colorectal cancer (CRC) represents a serious publichealth problem, ranking second in both incidence and mortality.Evaluation of DNA mismatch repair system (MMR) status is highlyrelevant in CRC due to its prognostic and predictive impact. Re-gardless of its clinical utility in CRC, implementation of deficientMMR (dMMR) status assessment in our health system has beenpartial, and its prevalence in our hospital cohorts is unknown. Ouraim was to determine the prevalence of MMR deficiency (dMMR) in CRC samples from the Hospital “El Cruce” (HEC) and to integratethe obtained results with other available clinical-pathological datain a customized digital registry based on the “Research ElectronicData Capture” web platform (RedCap). Presence of MMR proteins(MLH1, PMS2, MSH2 and MSH6) was assessed by immunohisto-chemistry in an ambispective study on FFPE CRC samples obtainedfrom endoscopic biopsies or surgical specimens. As a result, afterassessing immunoreactivity for all 4 MMR-related enzymes in 50clinical cases we observed a 14% prevalence of CRC tumors withdMMR status. The percentage distribution of dMMR type accordingto affected enzyme/s was: dMMR type 1 (MLH1-and PMS2-) 43%;type 2 (PMS2-) 29%; type 3 (MSH2-and MSH6-) 14%; type 4 (MSH6-) 0%; and other types of less prevalent dMMR tumors (in this caseMLH1-) 14%. At the descriptive level, for dMMR CRC patients, stageIII disease (43%) was the most common diagnosis, and distal colon(71.4%), particularly sigmoid colon (28,6%), was the most prevalenttumor location. Interestingly, poorly differentiated adenocarcinomaswere more commonly found in the dMMR group (dMMR 28.6 ver-sus pMMR 6.9%). Patient age, sex, chemotherapy regime, diseaserecurrence, biomarkers, among other clinical-pathological variables,were also integrated in RedCap. MMR status testing could lead tobetter therapeutic management and risk stratification and should beincluded in the diagnostic work-up of all CRC cases.