Comparison of Germline Genetic Testing Before and After a Medical Policy Covering Universal Testing Among Patients With Colorectal Cancer

Key Points

Question

Do patients with colorectal cancer (CRC) receive microsatellite instability and/or immunohistochemistry (MSI/IHC) tumor screening and germline genetic testing (GGT) when they have insurance that covers these tests?

Findings

In a cohort study of 9066 patients with CRC in 2017 to 2020, 2288 (25.2%) did not receive MSI/IHC despite being eligible for coverage. In a cohort of 55 595 patients with CRC diagnosed in 2020 and covered by insurance, 1675 (3.0%) received GGT, and 1 in 6 patients had variants that were clinically actionable.

Meaning

These results indicate that medical policies that provide universal testing for MSI/IHC tumor screening and GGT were underused for patients with CRC, potentially impeding their access to precision therapy, clinical trials, and evidence-based clinical management.

Abstract

This cohort study of claims data examines whether uptake of microsatellite instability and/or immunohistochemistry tumor screening germline genetic testing for patients with colorectal cancer has improved since implementation of universal coverage by insurance policies.

Abstract

Importance

In 2020, some health insurance plans updated their medical policy to cover germline genetic testing for all patients diagnosed with colorectal cancer (CRC). Guidelines for universal tumor screening via microsatellite instability and/or immunohistochemistry (MSI/IHC) for mismatch repair protein expression for patients with CRC have been in place since 2009.

Objectives

To examine whether uptake of MSI/IHC screening and germline genetic testing in patients with CRC has improved under these policies and to identify actionable findings and management implications for patients referred for germline genetic testing.

Design, Setting, and Participants

The multicenter, retrospective cohort study comprised 2 analyses of patients 18 years or older who were diagnosed with CRC between January 1, 2017, and December 31, 2020. The first analysis used an insurance claims data set to examine use of MSI/IHC screening and germline genetic testing for patients diagnosed with CRC between 2017 and 2020 and treated with systemic therapy. The second comprised patients with CRC who had germline genetic testing performed in 2020 that was billed under a universal testing policy.

Main Outcomes and Measures

Patient demographic characteristics, clinical information, and use of MSI/IHC screening and germline genetic testing were analyzed.

Results

For 9066 patients with newly diagnosed CRC (mean [SD] age, 64.2 [12.7] years; 4964 [54.8%] male), administrative claims data indicated that MSI/IHC was performed in 6645 eligible patients (73.3%) during the study period, with 2288 (25.2%) not receiving MSI/IHC despite being eligible for coverage. Analysis of a second cohort of 55 595 patients with CRC diagnosed in 2020 and covered by insurance found that only 1675 (3.0%) received germline genetic testing. In a subset of patients for whom germline genetic testing results were available, 1 in 6 patients had pathogenic or likely pathogenic variants, with most of these patients having variants with established clinical actionability.

Conclusions and Relevance

This nationwide cohort study found suboptimal rates of MSI/IHC screening and germline genetic testing uptake, resulting in clinically actionable genetic data being unavailable to patients diagnosed with CRC, despite universal eligibility. Effective strategies are required to address barriers to implementation of evidence-based universal testing policies that support precision treatment and optimal care management for patients with CRC.