Gaps in Incorporating Germline Genetic Testing Into Treatment Decision-Making for Early-Stage Breast Cancer

Abstract

Purpose Genetic testing for breast cancer risk is evolving rapidly, with growing use of multiple-gene panels that can yield uncertain results. However, little is known about the context of such testing or its impact on treatment. Methods A population-based sample of patients with breast cancer diagnosed in 2014 to 2015 and identified by two SEER registries (Georgia and Los Angeles) were surveyed about genetic testing experiences (N = 3,672; response rate, 68%). Responses were merged with SEER data. A patient subgroup at higher pretest risk of pathogenic mutation carriage was defined according to genetic testing guidelines. Patients' attending surgeons were surveyed about genetic testing and results management. We examined patterns and correlates of genetic counseling and testing and the impact of results on bilateral mastectomy (BLM) use. Results Six hundred sixty-six patients reported genetic testing. Although two thirds of patients were tested before surgical treatment, patients without private insurance more often experienced delays. Approximately half of patients (57% at higher pretest risk, 42% at average risk) discussed results with a genetic counselor. Patients with pathogenic mutations in BRCA1/2 or another gene had the highest rates of BLM (higher risk, 80%; average risk, 85%); however, BLM was also common among patients with genetic variants of uncertain significance (VUS; higher risk, 43%; average risk, 51%). Surgeons' confidence in discussing testing increased with volume of patients with breast cancer, but many surgeons (higher volume, 24%; lower volume, 50%) managed patients with BRCA1/2 VUS the same as patients with BRCA1/2 pathogenic mutations. Conclusion Many patients with breast cancer are tested without ever seeing a genetic counselor. Half of average-risk patients with VUS undergo BLM, suggesting a limited understanding of results that some surgeons share. These findings emphasize the need to address challenges in personalized communication about genetic testing.

Fig 1.

Results from logistic regression model on the likelihood of receiving bilateral mastectomy (BLM). The model also controlled for geographic site as a potential confounder.

Fig 2.

Adjusted probability of receiving bilateral mastectomy and its 95% CI according to genetic testing results and patient pretest risk for genetic mutation carriage. This figure depicts adjusted probability of receiving bilateral mastectomy by the genetic testing results and pretesting risk levels, based on results from a logistic regression model on the likelihood of receiving bilateral mastectomy, controlling for the significant confounders of age, race, insurance type, and site. The adjusted probability is calculated for a typical patient who is non-Hispanic white, is older than age 50 years, and has private insurance.

Fig 3.

Attending surgeons’ perspectives on referral to genetic counseling, ordering genetic tests, and managing test results, according to surgeons’ volume of newly diagnosed patients with breast cancer seen in the past year. BCS, breast-conserving surgery; VUS, variant of uncertain significance.

Fig A1.

Patient flow diagram depicting the flow of patients into the study from those initially identified to the final analytic sample.