Treatment-Focused Rapid Genetic Testing in Breast Cancer

Background and purpose: Testing for breast cancer-associated genetic mutations has traditionally been performed in Australia after the patient's initial surgery, likely due to the lengthy period required to receive results. Recent advances in genetic testing now allows for 'rapid' testing where a result can be provided in 30 days or earlier, allowing for treatment-focused testing prior to initial surgery that can be used to guide management decisions, including the decision to perform mastectomy rather than breast conserving surgery, as well as prophylactic contralateral mastectomy. We reviewed our experience with treatment focused genetic testing to assess how often this was utilised and how frequently a mutation was identified. Methods: All patients with breast cancer referred to the St Vincent's Hospital Cancer Genetic Service from 2015 to 2020 where rapid genetic testing was requested and where the results of the testing were returned within 30 days were reviewed. Patient demographics, the time taken for a result to be known and the details of any pathogenic mutations or variants of uncertain significance were recorded. Results: From 2015 to 2020 there were 187 patients with breast cancer where genetic testing results were requested and returned within 30 days. Median age (IQR) was 57 (47-67). There were 184 females (98%) and 3 males (2%). Mean time (sd) to results was 20 (7.4) days, range 8-30. Pathogenic mutations were identified in 11 cases (5.8%) affecting BRCA1 in 5, BRCA2 in 4, TP53 in 1 and PALB2 in 1. Variants of uncertain significance were identified in a further 14 cases (7.5%). The annual number of cases where rapid testing was performed showed no trend, varying from 19 to 41 cases per year. Conclusion: Treatment focused 'rapid' genetic testing accounted for only a small proportion of cases referred for genetic testing at our institution, and the number has not been increasing since 2015. Genetic testing prior to initial surgery can guide decision making and may reveal a pathogenic mutation in almost 6% of cases. Clinicians should consider treatment focused testing prior to initial surgery in all patients at higher risk of carrying a genetic mutation.