Moving breast cancer susceptibility gene testing into the mainstream

Timely delivery of results to guide index cancer treatment and greater equity of access are among the goals of broader testing

Testing for breast cancer susceptibility genes has evolved dramatically over the past three decades. BRCA1/2 genetic testing was introduced soon after the genes were identified in the mid‐1990s, but the process was labour‐intensive, expensive, and took many months to complete, making restrictive eligibility criteria necessary. Genetic counselling typically took place in hereditary cancer clinics in medical genetics departments, where women in families at high risk of breast cancer were offered risk assessment and genetic testing. But as women with breast cancer were treated in surgery and oncology departments, decoupling of genetic testing from the cancer care treatment pathway was typical. For those with pathogenic variants in breast cancer susceptibility genes, increased surveillance and prevention of subsequent cancers was the main motive for women and their families, as genetic testing results were seldom available in time to alter primary local or systemic therapy decisions.1 Next generation sequencing, together with legal decisions determining that human genes are not patentable, has expanded access to genetic testing, which is now more efficient, of greater capacity, and scalable. A variety of breast cancer susceptibility genes are assessed with multi‐gene panels, including not only BRCA1/2, but also PALB2, TP53, ATM, and CHEK2, among others. Commensurate with improved capacity for testing, the cancer genetics community has ushered in the era of “mainstream genetic testing”, whereby people with newly diagnosed cancer are offered access to genetic testing as part of a program of initial investigations with both prognostic and predictive potential.