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With our ever-growing understanding of mutations that increase cancer risk and the rise of targeted treatments such as poly (ADP-ribose) polymerase (PARP) inhibitors that are indicated for specific mutations, the use of germline genetic testing for patients with breast cancer has increased significantly in recent years. How are these test results affecting patients' treatment? In a population-based cohort study published recently published in JAMA Oncology, Allison W. Kurian, MD, MSc, and colleagues found that patients with breast cancer whose germline genetic testing reveals pathogenic mutations often receive treatment that deviates from the guidelines. In this interview with i3 Health, Dr. Kurian, Director of the Stanford Women's Clinical Cancer Genetics Program, discusses the importance of these results and shares advice for oncologists seeking to determine the appropriate treatment for patients with breast cancer who are carriers of pathogenic mutations.
What prompted you to pursue this investigation?
Allison W. Kurian, MD, MSc: As an oncologist and cancer genetics physician, I know there has been rapid change in the use of genetic testing after a cancer diagnosis. Our research team thought it would be important to understand more about how genetic testing results are affecting cancer treatment.
Can you explain the significance of your findings?
Dr. Kurian: We used a very large, population-based dataset encompassing two diverse states, with cancer registries that do not leave anyone out. We obtained genetic results directly from the testing laboratories and linked them to cancer registry data. Using this rigorous study design, we learned that women with inherited pathogenic variants in cancer risk genes have distinct patterns of breast cancer treatment: specifically, they have more use of bilateral mastectomy and chemotherapy and less use of radiotherapy after breast-conserving surgery. This may have implications for the health outcomes of these breast cancer patients.
You mention in your study that the treatment pattern in pathogenic variant carriers appears to be less guideline concordant, especially regarding practices for radiotherapy and chemotherapy. How might this departure from guidelines be impacting patient outcomes?
Dr. Kurian: Practice guidelines are based on randomized clinical trials that demonstrate a treatment's efficacy. However, most of the trials that inform current guidelines did not include genetic testing of participants to identify carriers of inherited pathogenic variants. We do not know whether the observed departure from guidelines is associated with worse patient outcomes among pathogenic variant carriers. We will investigate this question in our future work.
What advice can you share with community oncologists as they make decisions regarding which patients with breast cancer should undergo genetic testing and as they determine the appropriate course of treatment for patients with pathogenic variants?
Dr. Kurian: I would advise following practice guidelines about which breast cancer patients to test, with the understanding that these guidelines are evolving rapidly. I think we should be cautious about treating pathogenic variant carriers differently from other breast cancer patients, unless evidence emerges to support doing so.
About Dr. Kurian
Allison W. Kurian, MD, MSc, a medical oncologist and epidemiologist, is an Associate Professor of Medicine and of Health Research and Policy at Stanford University School of Medicine, where she is the Director of the Stanford Women's Clinical Cancer Genetics Program. Dr. Kurian's research focuses on identifying women with elevated breast and gynecologic cancer risk and on developing and evaluating techniques for early cancer detection and risk reduction.
For More Information
Kurian AW, Ward KC, Abrahamse P, et al (2020). Association of germline genetic testing results with locoregional and systemic therapy in patients with breast cancer. JAMA Oncol. [Epub ahead of print] DOI:10.1001/jamanetworkopen.2019.20471
Transcript edited for clarity. Any views expressed above are the speaker's own and do not necessarily reflect those of i3 Health.