Genetic analyses identify more mutations and help plan treatment for breast cancer

Genetic analyses identify more mutations and help plan treatment for breast cancer
Genetic analyses identify more mutations and help plan treatment for breast cancer

Three studies from Myriad Genetics Inc were presented at the 2014 San Antonio Breast Cancer Symposium (SABCS).

In the first study, the myRisk Hereditary Cancer test was able to detect 105% more mutations in cancer-causing genes than conventional BRCA testing alone.

An analysis of 17,142 patients with breast cancer showed that 9.5% of females (n=1,608) were positive for at least one deleterious or suspected deleterious gene mutation. The myRisk Hereditary Cancer test found BRCA1 and BRCA2 comprised 49% of the identified mutations, and 51% of the mutations were in other genes, representing a 105% increase in mutation detection over BRCA testing alone.

Many of these newly identified mutations were in other breast cancer genes such as: PALB2, CHEK2, ATM, and NBN. In addition, less than 1% of patients had a mutation in a gene not associated with breast cancer, reducing any concerns about unanticipated results.

Myriad also presented two key studies in triple negative breast cancer (TNBC) that show the myChoice HRD test accurately predicted response to platinum-based therapy in patients with early stage TNBC and that the BRACAnalysis molecular diagnostic test significantly predicted response to platinum-based drugs in patients with metastatic TNBC.

In the second study, researchers at Dana-Farber Cancer Institute in Boston, Massachusetts, and several other leading cancer research institutions validated the use of the myChoice HRD test in the neoadjuvant setting with TNBC. 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 HRD (P=.001). Importantly, 28% of patients in the deficient HRD group had a pathologic complete response compared to none in the intact HRD group.

myChoice HRD may assist in selecting the best chemotherapy for TNBC patients before they have surgery when there is the greatest opportunity to affect a positive outcome. Patients with a deficient HRD status are likely to respond to platinum-based therapies, while patients with an intact HRD state are unlikely to respond and could be spared the added toxicity associated with these medicines.

In the third study, researchers at the UK-based Institute for Cancer Research evaluated the use of companion diagnostic assays to evaluate 310 patients with metastatic TNBC. Their goal was to identify which patients would respond to carboplatin or docetaxel.

A key finding from this analysis is that BRACAnalysis showed that 68% of patients with a germline BRCA mutation had an objective response to treatment with carboplatin, compared with only 33% of patients who received docetaxel (P=.03). Importantly, there was no difference between carboplatin and docetaxel in patients without a germline BRCA mutation.

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