A Canadian Provincial Screening Program for Lynch Syndrome

Manitoba implemented the first Canadian provincial program of reflex screening through mismatch repair immunohistochemistry (MMR-IHC) for all colorectal cancers diagnosed at age 70 years or younger in December 2017. We evaluated compliance to universal reflex testing and for referrals to Genetics for individuals with MMR-deficient tumors.

We searched the provincial pathology database with "adenocarcinoma" in the colorectal specimen pathology reports between March 2018 and December 2020. We cross-referenced with paper and electronic records in the Program of Genetics and Metabolism to determine whether patients with MMR-deficient tumors had been referred for Genetic assessment and what proportion of patients and first-degree relatives accepted an appointment and genetic testing. We performed logistic regression analysis to identify predictors of testing.

We identified 3,146 colorectal adenocarcinoma specimens (biopsies and surgical resections) from 1,692 unique individuals (mean age 68.66 years, male 57%). Of those aged 70 years or younger (n = 936), 89.4% received MMR-IHC screening. Individual pathologists (categorized by the highest, average, and lowest screening rates) were the biggest predictors of MMR-IHC screening on multivariable analysis (highest vs lowest: odds ratio 17.5, 95% confidence interval 6.05-50.67). While only 53.4% (n = 31) of 58 screen-positive cases were referred by pathologists for genetic assessment, other clinicians referred an additional 22.4% (n = 13), resulting in 75.8% overall referral rate of screen-positive cases. Thirteen (1.4%) patients (1.1%, aged 70 years or younger) were confirmed to experience Lynch syndrome through germline testing, and 8 first-degree relatives (an average of 1.6 per patient) underwent cascade genetic testing.

The first Canadian Lynch syndrome screening program has achieved high rates of reflex testing.