McGill-Led Study Reveals Universal Genetic Testing Could Help Identify Missed Candidates for Advanced Breast Cancer Therapies

A new study demonstrates how universal genetic testing for breast cancer can ensure no patient is missed for advanced therapies.

In a Canadian first, researchers led by William Foulkes, Distinguished James McGill Professor in McGill University’s Departments of Medicine, Oncology, and Human Genetics, tested over 700 women diagnosed with invasive breast cancer for genetic mutations associated with an increased risk for breast cancer, regardless of age or family history. The women were from diverse backgrounds.

About four per cent were found to carry gene mutations that make them strong candidates for targeted therapies such as PARP inhibitors, which block cancer cell growth and reduce the chance of cancer returning.

In Canada, genetic testing has been typically restricted to those with a strong family history of breast cancer or those diagnosed at a young age.

“By testing everyone, an approach known as universal testing, we bypassed the need for detailed risk assessments that can exclude patients who could benefit,” said Foulkes, a cancer geneticist at the Research Institute of the McGill University Health Centre and the Lady Davis Institute for Medical Research.

“Identifying mutations early allows us to customize treatment plans based on a patient’s unique genetic profile.”

More vs. meaningful testing

The findings published in JAMA Network Open shed light on the gaps in testing practices and their impact on patient care.

They also raise the question of whether universal genetic testing should be implemented in Canada.

The researchers caution that adopting universal genetic testing within Canada’s public health-care system would be a challenge, even as the cost of testing has dropped significantly.

“More isn’t always more,” Foulkes noted. “It’s about ensuring that the testing we do leads to tangible benefits for patients, without overburdening the system. The key question is not just who should be tested, but what genes we should focus on.”

As health-care policies evolve, the researchers say testing for BRCA1, BRCA2 and PALB2 should be prioritized, as mutations in these genes have the greatest impact on treatment decisions and patient outcomes.

The team’s next phase of research will explore genetic testing at the population level, starting with unaffected women over age 30. This study, conducted at Montreal’s Jewish General Hospital, McGill University Health Centre, and St. Mary’s Hospital, was made possible by the collaboration of a dedicated team, including Dr. Stephanie Wong and Dr. George Chong. It was funded by the Jewish General Hospital Foundation and Quebec Breast Cancer Foundation.