When Should Patients Undergo Genetic Testing for Hereditary Colon Cancer Syndromes?

Approach to Familial Predisposition to Colorectal Cancer

The traditional approach of one-size-fits-all for colorectal cancer has been replaced by personalized interventions to an individual's unique genetic, molecular, and environmental profile, seeking to identify high-risk individuals who would benefit from individualized screening and surveillance. This change in approach is due, in part, to emerging technologies, such as next-generation DNA sequencing.

Screening and prevention of colorectal cancer

Mortality from colorectal cancer is reduced through screening and early detection; moreover, removal of neoplastic lesions can reduce cancer incidence. While understanding of the risk factors, pathogenesis, and precursor lesions of colorectal cancer has advanced, the cause of the recent increase in cancer among young adults is largely unknown. Multiple invasive, semi- and non-invasive screening modalities have emerged over the past decade. The current emphasis on quality of colonoscopy has improved the effectiveness of screening and prevention, and the role of new technologies in detection of neoplasia, such as artificial intelligence, is rapidly emerging. The overall screening rates in the US, however, are suboptimal, and few interventions have been shown to increase screening uptake. This review provides an overview of colorectal cancer, the current status of screening efforts, and the tools available to reduce mortality from colorectal cancer.

Comparison of Universal Genetic Testing vs Guideline-Directed Targeted Testing for Patients With Hereditary Cancer Syndrome

IMPORTANCE

Hereditary factors play a key role in the risk of developing several cancers. Identification of a germline predisposition can have important implications for treatment decisions, risk-reducing interventions, cancer screening, and germline testing.

OBJECTIVE

To examine the prevalence of pathogenic germline variants (PGVs) in patients with cancer using a universal testing approach compared with targeted testing based on clinical guidelines and the uptake of cascade family variant testing (FVT).

DESIGN, SETTING, AND PARTICIPANTS

This prospective, multicenter cohort study assessed germline genetic alterations among patients with solid tumor cancer receiving care at Mayo Clinic cancer centers and a community practice between April 1, 2018, and March 31, 2020. Patients were not selected based on cancer type, disease stage, family history of cancer, ethnicity, or age.

EXPOSURES

Germline sequencing using a greater than 80-gene next-generation sequencing platform.

MAIN OUTCOMES AND MEASURES

Proportion of PGVs detected with a universal strategy compared with a guideline-directed approach and uptake of cascade FVT in families.

RESULTS

A total of 2984 patients (mean [SD] age, 61.4 [12.2] years; 1582 [53.0%] male) were studied. Pathogenic germline variants were found in 397 patients (13.3%), including 282 moderate- and high-penetrance cancer susceptibility genes. Variants of uncertain significance were found in 1415 patients (47.4%). A total of 192 patients (6.4%) had incremental clinically actionable findings that would not have been detected by phenotype or family history-based testing criteria. Of those with a high-penetrance PGV, 42 patients (28.2%) had modifications in their treatment based on the finding. Only younger age of diagnosis was associated with presence of PGV. Only 70 patients (17.6%) with PGVs had family members undergoing no-cost cascade FVT.

CONCLUSIONS AND RELEVANCE

This prospective, multicenter cohort study found that universal multigene panel testing among patients with solid tumor cancer was associated with an increased detection of heritable variants over the predicted yield of targeted testing based on guidelines. Nearly 30% of patients with high-penetrance variants had modifications in their treatment. Uptake of cascade FVT was low despite being offered at no cost.

NCCN Guidelines Insights: Genetic/Familial High-Risk Assessment: Colorectal, Version 2.2019

Identifying individuals with hereditary syndromes allows for improved cancer surveillance, risk reduction, and optimized management. Establishing criteria for assessment allows for the identification of individuals who are carriers of pathogenic genetic variants. The NCCN Guidelines for Genetic/Familial High-Risk Assessment: Colorectal provide recommendations for the assessment and management of patients with high-risk colorectal cancer syndromes. These NCCN Guidelines Insights focus on criteria for the evaluation of Lynch syndrome and considerations for use of multigene testing in the assessment of hereditary colorectal cancer syndromes.