Genetic Tests for Breast Cancer Detect More Mutations

A new study has demonstrated the ability of a commercial Hereditary Cancer test to detect 105% more mutations in cancer causing genes than conventional Breast Cancer (BRCA) testing alone.

The company also presented two key studies in triple negative breast cancer (TNBC) that show that another test accurately predicted response to platinum-based therapy in patients with early-stage TNBC and that their molecular diagnostic test significantly predicted response to platinum-based drugs in patients with metastatic TNBC.

An analysis of 17,142 patients with breast cancer showed 1,608 (9.5%) females were positive for at least one deleterious or suspected deleterious gene mutation. The myRisk Hereditary Cancer test (Myriad Genetics, Inc.; Salt Lake City, UT, USA) found BRCA1 and BRCA2 comprised 49% of the identified mutations, and 50% percent of the mutations were in other genes, representing a 105% increase in mutation detection over BRCA testing alone.

Scientists at the at Dana-Farber Cancer Institute (Boston, MA, USA) and several other leading cancer research institutions validated the use of Myriad’s myChoice HRD test in the neoadjuvant setting with TNBC. The myChoice HRD is the first and only comprehensive companion diagnostic test to detect a DNA scar in tumor that is indicative of a dysfunctional DNA repair pathway. The study results demonstrated that 52% of patients with a deficiency defined by myChoice HRD responded to platinum-based treatment compared to only 10% of patients with intact homologous recombination deficiency (HRD). Importantly, 28% of patients in the deficient HRD group had a pathologic complete response compared to none in the intact HRD group.

Scientists at the Institute for Cancer Research (Sutton, UK) evaluated the use of companion diagnostic assays to evaluate 310 patients with metastatic TNBC to identify which patients would respond to carboplatin or docetaxel. A key finding from this analysis is that another of Myriad’s tests, BRACAnalysis, showed that 68% of patients with a germline BRCA mutation had an objective response to treatment with carboplatin, compared to only 33% of patients who received docetaxel. Importantly, there was no difference between carboplatin and docetaxel in patients without a germline BRCA mutation.

Richard Wenstrup, MD, chief medical officer, Myriad Genetic Laboratories, said, “Our myRisk Hereditary Cancer test is making a major scientific contribution to our understanding of hereditary cancer risk and more importantly to patient care. We believe panel testing provides valuable information and guidance both for the management of the patient and the patient's family members.” The studies were presented at the 37th Annual San Antonio Breast Cancer Symposium (SABCS), held December 9–13, 2014, in San Antonio (TX, USA).

Related Links:
Myriad Genetics, Inc.
Dana-Farber Cancer Institute
Institute for Cancer Research