Testing positive for a high-risk breast cancer gene doesn’t always lead to the most appropriate care, a new study finds. Women who tested positive for such variants were more likely to receive bilateral mastectomy, which is in line with current guidelines. But they were also less likely to receive radiotherapy after lumpectomy, and more likely to receive chemotherapy for early-stage hormone receptor-positive disease, steps which don’t align with standard treatment guidelines.
Tracking these trends is especially important since more women are receiving genetic testing when they’re diagnosed with early stage breast cancer and treatment options are expanding.
“Cancer treatment options are increasingly more complex for patients. Patients must consider a myriad of treatment options for the cancer they have and the implications of genetic test results on cancer prevention strategies for themselves and their family members,” says Steven J. Katz, M.D., MPH, and senior author of a study led by the University of Michigan Rogel Cancer Center and Stanford University School of Medicine.
“We found that breast cancer treatment among women who test positive for an inherited genetic mutation is less in line with practice guidelines, in particular for radiation therapy and chemotherapy,” says lead study author Allison W. Kurian, M.D., M.Sc., associate professor of medicine and of health research and policy at Stanford.
Certain mutations substantially increase the risk of developing a second breast cancer. The most well studied heritable mutations that increase breast cancer risk are in the BRCA1 and BRCA2 genes. Most womenwho have a such mutations, are diagnosed with Hereditary Breast and Ovarian Cancer (HBOC) syndrome, which gives them up to an 87% chance of developing breast cancer. But there are a growing number of genetic tests for breast cancer that include other genes as well.
“It’s challenging to integrate genetic testing into breast cancer care,” says Kurian. The significance of the results and future impact on the patient’s risk vary widely while meanwhile we must focus on eliminating the cancer the patient faces today.”
For this study researchers collected information from the Georgia and California Cancer Registries for 20,568 women diagnosed with early stage breast cancer and matched it to genetic testing results. Next they looked at the characteristics of patients’ tumors to assess what the recommended treatment options would be based on standard guidelines. Then they compared actual treatments for women who tested positive for BRCA1 or BRCA2 mutations to those of women who tested positive for other genes associated with breast cancer, and those whose tests were negative or identified a variant not known to increase breast cancer risk. They found distinct differences in surgery, radiation and chemotherapy treatments among women who were positive for an inherited genetic mutation.
Specifically: 66% of BRCA-positive patients underwent double mastectomy, compared to 24% of patients with a negative genetic test. While 51% of BRCA-positive patients who were candidates for radiation received it, compared to 82% of patients with a negative genetic test Chemotherapy. Also, 38% of BRCA-positive patients who were candidates to forgo chemotherapy got it, compared to 30% of patients with a negative genetic test.
The observed relationship of surgical treatment to genetic test results are in line with guidelines supporting double mastectomy as an effective strategy to prevent future cancer risk. But guidelines do not recommend using genetic testing results to determine whether radiation or chemotherapy are needed to treat the diagnosed cancer.
The gaps in radiation were particularly striking, as radiation after lumpectomy is considered key to achieving the best outcome with breast conservation. The researchers propose that some patients may have skipped radiation because they intended to have a mastectomy in the future. Another explanation could be concern about whether radiation would increase cancer risk for these patients.
“We need to understand this gap better, because it could have potential implications on patients’ outcomes,” says Katz, professor of general medicine and of health management and policy at the University of Michigan.
“Our findings should reinforce that physicians who treat cancer need to be increasingly attentive to the clinical implications of genetic testing after diagnosis. Test results must be optimally integrated into the patient’s treatment to manage her cancer today and her risk in the future,” Kurian says.
