Myriad’s myChoice HRD test is the first and only companion diagnostic to measure three modes of homologous recombination deficiency (HRD) including loss of heterozygosity, telomeric allelic imbalance and large-scale state transitions in cancer cells.

The myChoice HRD score is a biomarker that indicates the inability of cancer cells to repair DNA damage and reflects a tumor’s sensitivity to DNA-damaging medicines such as PARP (poly-ADP ribose polymerase) inhibitors and platinum-based therapies.

"The myChoice HRD companion diagnostic test stems from Myriad’s pioneering research and is a real step forward in realizing the goal of personalized medicine for patients with ovarian, breast and pancreatic cancers and possibly other solid tumors," said Jerry Lanchbury, Ph.D., chief scientific officer, Myriad.

Melinda Telli, M.D. (Stanford University School of Medicine) will present new clinical data that established a homologous recombination (HR) deficiency threshold that can identify 95% of patients with mutations in BRCA1/2 and other homologous recombination genes and who have a higher likelihood of responding to treatment with DNA-damaging agents.

Specifically, the study validated an HRD threshold score of >=42 (on a scale of 0-100) using a training cohort of 497 breast and 561 ovarian cancer patients. A myChoice HRD test score >=42 represents a positive score or a loss of DNA repair function, while a myChoice HRD score <42 reflects a negative score or an intact DNA repair function.

Using this threshold, the myChoice HRD test was then evaluated to predict response to neoadjuvant platinum-based chemotherapy in patients with TNBC or BRCA1/2 mutation-associated breast cancer. The endpoints of this analysis were residual cancer burden (RCB) and pathological complete response (pCR).

The results showed that a positive myChoice HRD score and/or a BRCA1/2 mutation were statistically significantly associated with treatment response (Table 1), and importantly, the myChoice HRD test identified responders lacking a deleterious BRCA1/2 mutation. In this study, myChoice HRD predicted nearly double the number of patients who would likely respond to neoadjuvant platinum-based chemotherapy compared to BRCA1/2 mutations alone or other clinical features.