Underutilization of Lynch Syndrome Screening at Two Large Veterans Affairs Medical Centers

A Canadian Provincial Screening Program for Lynch Syndrome

INTRODUCTION

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.

METHODS

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.

RESULTS

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.

DISCUSSION

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

Systems approach to enhance Lynch syndrome diagnosis through tumour testing

BACKGROUND

Guidelines recommend universal mismatch repair (MMR) tumour testing of colorectal adenocarcinomas (CRCs) to screen for Lynch syndrome (LS). However, its implementation remains disjointed and referral for genetic testing dismal, particularly among minorities. We aimed to increase referral, cancer genetic testing and eventually LS diagnosis by developing the CLEAR LS (Closed Loop Enhanced Assessment and Referral for Lynch Syndrome) intervention, a systems approach which in the second phase was automated.

METHODS

This is a cohort study of all patients diagnosed with CRC at an academic centre between 1 January 2012, when implementation of universal CRC testing began, and 31 January 2021. The original cohort spanned through 31 May 2015. Tumour testing included MMR immunohistochemistry, followed by BRAF V600E/MLH1 promoter methylation testing when indicated. The intervention included a manual phase (1 June 2015 through 31 July 2018), which systematised pathology screening and cancer genetics (CG) referral mechanisms, and an automated phase (1 August 2018 through 31 January 2021) using computer programming.

RESULTS

A total of 249/1541 CRC (17.38%) had MMR loss of expression and 129 (8.37%) qualified for CG evaluation. Referral was 27.58% in the original cohort and 92.1% in the intervention (p<0.001). Patients seen by CG among referred were 27.58% in the original cohort and 74.3% in the intervention (p two-sided<0.001). The distribution of race/ethnicity among patients qualifying and referred for CG evaluation was not significantly different across cohorts. LS diagnosis increased from 0.56% (original cohort) to 1.43% (intervention). Cost per new diagnosis of LS decreased from US$173 675 to $87 960 from original cohort to intervention.

CONCLUSION

Implementation of systematic case identification and referral support mechanisms significantly increased the proportion of patients undergoing genetic testing and doubled the percentage of patients diagnosed with LS with no referral differences across racial/ethnic groups.

Underutilization of Guideline-Recommended Mismatch Repair/Microsatellite Instability Biomarker Testing in Advanced Colorectal Cancer

BACKGROUND

In 2017, DNA mismatch repair/microsatellite instability (MMR/MSI) testing was nationally recommended for advanced colorectal cancers based on favorable immune checkpoint inhibitor responses among patients with MMR-deficient/MSI-high tumors.

METHODS

Patients ages ≥20-years-old presenting with stage IV colorectal adenocarcinoma from 2010 to 2017 were identified from the National Cancer Database. 2017 was the latest year with available testing utilization data. Patient, tumor, socioeconomic, and care setting characteristics were evaluated for association with upfront MMR/MSI testing in 2017 using multivariable logistic regression and average adjusted predicted probabilities (%AAP).

RESULTS

Among 72,830 stage IV colorectal cancers, upfront MMR/MSI testing levels increased from 16.4% in 2010 to 56.4% in 2017. For patients diagnosed in 2017 (i.e., following national recommendations, n = 10,022), testing levels were lower for older patients (Padj &lt; 0.001), and were independent of patients' race/ethnicity and insurance status. Patients from the poorest quartile of households received less testing [49.6%AAP, 99.9% confidence interval (CI) 45.5-53.7] than patients from the 3rd (56.9%AAP, 99.9% CI, 53.3-60.6; Padj &lt; 0.001) or 4th quartiles (57.6%AAP, 99.9% CI, 54.3-60.9; Padj &lt; 0.001). Although testing levels improved most at community programs, they remained lower in 2017 (46.6%AAP, 99.9% CI, 41.0-52.1) compared with academic/NCI-designated comprehensive cancer centers (62.8%AAP, 99.9% CI, 59.7-65.8; Padj &lt; 0.001).

CONCLUSIONS

Upfront MMR/MSI testing utilization for patients with advanced colorectal cancer has increased but there is still substantial need for optimization. Testing utilization disproportionately lagged for patients who were older, from the poorest quartile of households, or managed at community cancer programs.

IMPACT

Our findings indicate opportunities for improving rates of MMR/MSI testing and reporting, possibly through incorporation into quality control and accreditation metrics.