Breast cancer: Multigene sequencing replaces BRCA tests

May 15, 2018 –An increasing number of women who are diagnosed with breast cancer are opting for multigene sequencing instead of the more limited testing for only BRCA1/ BRCA2 mutations, according to a new report.

The findings come from the ICanCAre study, published online May 10 in JAMA Oncology, which followed about 5000 women who had been diagnosed with stage 0-II breast cancer from 2013 to 2015.

About one quarter of these women underwent genetic testing of any kind. This number remained relatively constant throughout the 2-year study period. Among those who were tested, the proportion who underwent multigene testing steadily rose at a considerable rate.

About 26% of patients underwent multigene testing in 2013, but this percentage jumped to 66% within 2 years. In contrast, the percentage of women opting for BRCA-only testing declined from about 74% to 34% during the same period.

In general, multigene panel tests yield more clinically useful results and are rapidly becoming the norm, according to the lead author of this study, Dr. Kurian, associate professor of medicine and of health research and policy at Stanford University School of Medicine in California.

Thus, newly diagnosed women should ask their doctors whether they may be appropriate candidates for genetic testing. They should also advocate for the opportunity to discuss genetic testing and its implications with an experienced clinician, such as a genetic counselor, in a timely manner.

Whereas previously, the only cancer-related genes that were routinely sequenced were BRCA1 / BRCA2, panels are now available that can sequence up to 90 genes. But multigene sequencing is still quite new, and not much is known about the implications of such sequencing.

The ICanCare study had the goal of evaluating the uptake and outcomes of multigene sequencing in a large, contemporary cohort of breast cancer patients. Thus, women from the Surveillance, Epidemiology, and End Results Program (SEER) registries across Georgia and in Los Angeles, California, were surveyed, and the SEER data and results of clinical genetic testing (provided by four laboratories) were merged. The analysis included a racially diverse cohort of 5026 women. Of those patients, results of any kind of genetic testing were available for 1316 (26.2%); results of multigene sequencing were available for 588 patients; and results of BRCA1 / BRCA2 testing were available for 728 patients.

The authors of the study noted that there was a substantial change in the type of test that was selected, with multigene sequencing increasingly replacing BRCA1 / BRCA2-only testing. During the 2-year study period, the rate of multigene sequencing rose from 4.8% to 19.6%, while BRCA1 / BRCA2-only testing dropped from 22.6% to 10.0%.

Participants were asked about their experiences with testing. Genetic counselors were more likely to order multigene sequencing (25.5% vs 15.3%; P< .001), whereas surgeons frequently ordered both types of tests. Most testing was conducted prior to surgery, but women who underwent multigene sequencing were more likely to report that testing was delayed until after surgery (32.5% vs 19.9% for BRCA1 / BRCA2-only testing; P < .001).

Overall, according to Dr. Kurian, more genetic counselors are needed, and they should be integrated into routine cancer care. Interpretation of multigene panels is more complex and requires the expertise of genetic counselors, who are not always readily available, which could be partly responsible for the observed delay.

For the apomediary and daring patient, see here the study design and a list of 51 genes tested in the present panel, including the breast cancer susceptibility genes ATM,BRCA1, BRCA2, CDH1, CHEK2, NBN, NP1, PALP2, PTN, STK11, and TP53, as previously specified in the 2017 National Comprehensive Cancer Network (NCCN) Guidelines.

Note that this post has been adapted from an article in Medscape by Rosanne Nelson on May 14, 2018. All rights remain with Medscape.

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About the Author
thassodotcom Ph.D.; Professor in Pharmacology and Toxicology. Senior expert in theragenomic and personalized medicine and individualized drug safety. Senior expert in pharmaco- and toxicogenetics. Senior expert in human safety of drugs, chemicals, environmental pollutants, and dietary ingredients.

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