Reproductive Carrier Testing and Hereditary Cancer Risks
Heidi Owen, MS, CGC¹; Catherine Terhaar, MS, CGC¹; Lindsay Dohany, MS, CGC¹
1: Progenity, Ann Arbor, Michigan, United States
Patients who pursue carrier testing are interested in learning genetic information that could impact their risk to have a child affected with a genetic disorder. Expanded carrier testing panels test for many autosomal recessive or X-linked conditions. Patients who test positive are carriers, and typically do not have signs or symptoms associated with the condition. However, in some cases, carriers are at risk for specific symptoms, including an increased risk for cancer.
If an individual is found to be a carrier of a pathogenic variant in a gene that increases the risk of cancer, medical management recommendations may include increased surveillance, prophylactic surgeries, and chemoprevention, as well as genetic testing for at-risk relatives. We reviewed our experience with carrier testing in a large commercial laboratory to understand how often patients were identified with pathogenic variants that increased their cancer risks.
Progenity’s Preparent™ Global and Global+ carrier testing panels both test for over 200 hereditary disorders. Three genes in these panels (ATM, BLM, and FH) are included because they cause recessive disorders. These disorders include: ataxia telangiectasia for ATM homozygotes, Bloom syndrome for BLM homozygotes, and fumarase deficiency for FH homozygotes. However, heterozygous carriers of pathogenic variants in these genes also have a moderately increased risk for cancer. A retrospective review of carrier testing results was conducted from our commercial laboratory database.
Our review identified 11 carriers of an ATM pathogenic variant. Of these, 9 were females with ages ranging from 21 – 37 years. Additionally, 20 BLM pathogenic variant carriers were identified. Out of the 20 carriers, 17 were female and 3 were male. Their ages ranged from 18 – 39 years and the majority were of Ashkenazi Jewish ancestry. No FH carriers were identified. See Table 1 for demographic information.
Our experience demonstrates that identification of carrier status in genes associated with an increased cancer risk can occur. While these patients are not seeking testing for this purpose, these findings are possible and provide valuable insight into other health risks outside of the reproductive setting. For female ATM carriers, guidelines from the National Comprehensive Cancer Network (NCCN) recommend increased breast cancer surveillance (annual MRI in addition to mammogram) beginning at age 40, or earlier based on family history. Risk-reducing mastectomy may also be considered.
BLM carriers are at increased risk for colorectal cancer and should have a colonoscopy every 5 years beginning at age 40, according to NCCN guidelines. As seen in our cohort, carrier testing is typically performed prior to age 40, meaning that this information would be provided with time to implement recommended management changes.