Allison W. Kurian, MD, MSc
Women with early-stage breast cancer who test positive for an inherited genetic variant are not always receiving cancer treatment that follows current treatment guidelines, according to findings from a new study published by Allison W. Kurian, MD, MSc, and colleagues in JAMA Oncology.
An inherited gene can increase risk of developing a second breast cancer, so strategies such as mastectomy or oophorectomy are intended to prevent a future cancer, but women who have already been diagnosed with breast cancer must also consider how best to treat the existing tumor.
“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,” explained senior study author Steven J. Katz, MD, MPH.
More women are receiving genetic testing when they're diagnosed with early-stage breast cancer, with increasingly more sophisticated tests that include a panel of at least 30 different genes, each carrying different risks for future cancers.
“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,” said lead study author Dr. Kurian. “It's challenging to integrate genetic testing into breast cancer care. The significance of the results and future impact on the patient's risk vary widely, and meanwhile, we must focus on eliminating the cancer the patient faces today.”
“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."— Steven J. Katz, MD, MPH
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Methodology
Researchers collected information from the Georgia and California Cancer Registries on 20,568 women diagnosed with early-stage breast cancer and matched it to genetic testing results. All data was linked through an objective third party and deidentified for researchers to analyze.
Researchers looked at the characteristics of patients' tumors to assess what the recommended treatment options would be based on standard guidelines. They then compared actual treatments for women who tested positive for BRCA1 or BRCA2 mutations, those 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.
Results
The researchers found distinct differences in surgery, radiation, and chemotherapy treatment among women who were positive for an inherited genetic mutation.
Sixty-six percent of BRCA-positive patients underwent double mastectomy, compared to 24% of BRCA-negative patients; 51% of BRCA-positive patients who were candidates for radiation received it, compared to 82% of patients without a BRCA mutation; and 38% of BRCA-positive patients who were candidates to forgo chemotherapy actually received it, compared to 30% of BRCA-negative patients.
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. However, 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 noted by the authors, 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 intend to have a mastectomy in the future. Another explanation could be concern about whether radiation would increase cancer risk for these patients.
“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."— Allison W. Kurian, MD, MSc
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“We need to understand this gap better, because it could have potential implications on patients' outcomes,” said Dr. Katz.
“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,” concluded Dr. Kurian.
Disclosure: For full disclosures of the study authors, visit jamanetwork.com.
