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Penetrance estimates for BRCA1, BRCA2 (also applied to Lynch syndrome) based on presymptomatic testing: a new unbiased method to assess risk?

Accepted version
Peer-reviewed

Type

Article

Change log

Authors

Woodward, Emma 
Harkness, Elaine F 
Howell, Anthony 
Plaskocinska, Inga 

Abstract

PURPOSE: The identification of BRCA1, BRCA2 or mismatch repair (MMR) pathogenic gene variants in familial breast/ovarian/colorectal cancer families facilitates predictive genetic testing of at-risk relatives. However, controversy still exists regarding overall lifetime risks of cancer in individuals testing positive. METHODS: We assessed the penetrance of BRCA1, BRCA2, MLH1 and MSH2 mutations in men and women using Bayesian calculations based on ratios of positive to negative presymptomatic testing by 10-year age cohorts. Mutation position was also assessed for BRCA1/BRCA2. RESULTS: Using results from 2264 presymptomatic tests in first-degree relatives (FDRs) of mutation carriers in BRCA1 and BRCA2 and 646 FDRs of patients with MMR mutations, we assessed overall associated cancer penetrance to age of 68 years as 73% (95% CI 61% to 82%) for BRCA1, 60% (95% CI 49% to 71%) for BRCA2, 95% (95% CI 76% to 99%) for MLH1% and 61% (95% CI 49% to 76%) for MSH2. There was no evidence for significant penetrance for males in BRCA1 or BRCA2 families and males had equivalent penetrance to females with Lynch syndrome. Mutation position and degree of family history influenced penetrance in BRCA2 but not BRCA1. CONCLUSION: We describe a new method for assessing penetrance in cancer-prone syndromes. Results are in keeping with published prospective series and present modern-day estimates for overall disease penetrance that bypasses retrospective series biases.

Description

Keywords

Lynch syndrome, brca1, brca2, penetrance, pre-symptomatic, Adult, Aged, BRCA1 Protein, BRCA2 Protein, Bayes Theorem, Breast Neoplasms, Colorectal Neoplasms, Hereditary Nonpolyposis, Female, Genetic Predisposition to Disease, Genetic Testing, Humans, Male, Middle Aged, MutL Protein Homolog 1, MutS Homolog 2 Protein, Mutation, Ovarian Neoplasms, Penetrance, Risk Assessment

Journal Title

J Med Genet

Conference Name

Journal ISSN

0022-2593
1468-6244

Volume Title

55

Publisher

BMJ
Sponsorship
Department of Health (via National Institute for Health Research (NIHR)) (NF-SI-0616-10035)
Cancer Research UK (C20/A20976)
European Research Council (310018)