BRCA1 and BRCA2 genetic testing-pitfalls and recommendations for managing variants of uncertain clinical significance

Abstract

Background: Increasing use of BRCA1/2 testing for tailoring cancer treatment and extension of testing to tumour tissue for somatic mutation is moving BRCA1/2 mutation screening from a primarily prevention arena delivered by specialist genetic services into mainstream oncology practice. A considerable number of gene tests will identify rare variants where clinical significance cannot be inferred from sequence information alone. The proportion of variants of uncertain clinical significance (VUS) is likely to grow with lower thresholds for testing and laboratory providers with less experience of BRCA. Most VUS will not be associated with a high risk of cancer but a misinterpreted VUS has the potential to lead to mismanagement of both the patient and their relatives.

Design: Members of the Clinical Working Group of ENIGMA (Evidence-based Network for the Interpretation of Germline Mutant Alleles) global consortium (www.enigmaconsortium.org) observed wide variation in practices in reporting, disclosure and clinical management of patients with a VUS. Examples from current clinical practice are presented and discussed to illustrate potential pitfalls, explore factors contributing to misinterpretation, and propose approaches to improving clarity.

Results and conclusion: Clinicians, patients and their relatives would all benefit from an improved level of genetic literacy. Genetic laboratories working with clinical geneticists need to agree on a clinically clear and uniform format for reporting BRCA test results to non-geneticists. An international consortium of experts, collecting and integrating all available lines of evidence and classifying variants according to an internationally recognized system, will facilitate reclassification of variants for clinical use.

Keywords: BRCA; VUS; classification; clinical utility; variants of uncertain significance.

Figure 1.

Genetic variability information.

Figure 2.

Suggested model of a clinical pathway for breast and ovarian cancer patients. Initial genetic testing through an oncologist with basic training, expertise routinely contributed by the clinical genetics consultant. This model works where there is a close working relationship between oncologist and geneticist through a regular multidisciplinary team meeting.