Tumor BRCA Dx Could ID More Responders to PARP Inhibitors; Myriad Expects Initial Launch in Europe

The gist: Breast cancer patients with BRCA mutations could potentially be treated with new drugs called PARP inhibitors. In many cases, BRCA mutations are inherited, and are therefore found in all cells in the body. But a patient who did not inherit a BRCA mutation might still develop a mutation in a small number of cells, which might grow into a breast cancer tumor. Indeed, patients with ovarian and breast cancers have been identified who have BRCA mutations in their tumors only, but not in normal cells. Testing for BRCA mutations in tumor tissues could help identify more people who might benefit from treatment with PARP inhibitors.

“A comparison of germline BRCA mutation testing against a new diagnostic developed by Myriad Genetics that can gauge somatic mutations revealed that the latter was able to pick up 44 percent more deleterious markers in women with ovarian cancer.

“In identifying additional mutation carriers, Myriad hopes its so-called Tumor BRACAnalysis CDx will be able to identify more responders PARP inhibitors. The company has long-term plans to launch somatic BRCA mutation testing as a companion diagnostic first in Europe and then in the US.

“Germline mutations show up in all cells of the body, but a blood test that gauges just these mutations can miss some patients who acquire mutations only in their tumor. Gauging somatic mutations usually requires a test that analyzes markers in tumor tissue samples.

“At the European Society for Medical Oncology’s annual meeting in Madrid, Spain this week, researchers from Myriad and MD Anderson Cancer Center described a study analyzing approximately 130 previously untreated, high-grade ovarian cancer patients for germline BRCA mutations in blood samples and somatic mutations in tissue samples. In the study, the researchers also tested patients undergoing surgery for both of these types of mutations, and they performed germline testing using a custom amplicon assay and next-generation sequencing.”