Mismatch repair deficiency testing in patients with colorectal cancer and nonadherence to testing guidelines in young adults

Abstract

IMPORTANCE: Mismatch repair (MMR) deficiency of DNA has been observed in up to 15%of sporadic colorectal cancers (CRCs) and is a characteristic feature of Lynch syndrome, which has a higher incidence in young adults (age, <50 years) with CRC. Mismatch repair deficiency can be due to germline mutations or epigenetic inactivation, affects prognosis and response to systemic therapy, and results in unrepaired repetitive DNA sequences, which increases the risk of multiple malignant tumors. OBJECTIVE: To evaluate the utilization of MMR deficiency testing in adults with CRC and analyze nonadherence to long-standing testing guidelines in younger adults using a contemporary national data set to help identify potential risk factors for nonadherence to newly implemented universal testing guidelines. DESIGN, SETTING, AND PARTICIPANTS: Adult (age, <30 to ≥70 years) and, of these, younger adult (<30 to 49 years) patients with invasive colorectal adenocarcinoma diagnosed between 2010 and 2012 and known MMR deficiency testing status were identified using the National Cancer Database. The study was conducted from March 16, 2016, to March 1, 2017. EXPOSURES: Patient sociodemographic, facility, tumor, and treatment characteristics. MAIN OUTCOMES AND MEASURES: The primary outcome of interest was receipt of MMR deficiency testing. Multivariable logistic regression was used to identify independent predictors of testing in adult and/or young adult patients. RESULTS: A total of 152 993 adults with CRC were included in the study (78 579 [51.4%] men; mean [SD] age, 66.9 [13.9] years). Of these patients, only 43 143 (28.2%) underwent MMR deficiency testing; the proportion of patients tested increased between 2010 and 2012 (22.3%vs 33.1%; P