The abstract, titled “Utility of the 70-gene MammaPrint assay for prediction of benefit from extended letrozole therapy (ELT) in the NRG Oncology/NSABP B-42 trial” and presented by Dr. Priya Rastogi of the NSABP, detailed a retrospective evaluation of 1,866 samples, almost half of the original trial’s tissue samples, which were representative of the entire cohort. The data showed that genomic testing with MammaPrint could identify a subset of patients in the NSABP B-42 cohort who were most likely to benefit from ELT. Patients with a MammaPrint Low Risk profile had significantly better rates of distant recurrence (DR), disease-free survival (DFS) and breast cancer free interval (BCFI) when treated with extended endocrine therapy. Conversely, genomically High Risk patients did not see this same benefit and likely could have been spared extended endocrine therapy.

Patients with a genomic Low Risk result were stratified into Ultra Low Risk and Low Risk groups. The benefit of extended endocrine therapy was primarily observed in the Low Risk (non-Ultra Low) group. The benefit of extended endocrine therapy in these MammaPrint Low Risk patients ranged from a 4.0% improvement in DR rate to a 9.5% increase in DFS. MammaPrint was the only test that predicted a 52% relative benefit reduction in BCFI events (7.9% absolute benefit) and a 36% relative benefit reduction in DFS events (9.5% absolute benefit) with ELT. Another genomic test, the BCI-H/I ratio, evaluated samples from the NSABP B-42 trial and did not confirm the predictive value of BCI for the efficacy of extended endocrine therapy; further study is needed to evaluate the test’s predictive ability.

“By stratifying patients beyond High or Low Risk, we are able to see a larger breadth of difference in genomic signatures,” said Adam Brufsky, MD, PhD, Co-Director of the Women’s Cancer Center at Magee Women’s Hospital of UPMC Hillman Cancer Center. “More granular information such as this allows us to better understand the biology of a tumor, and gets us closer to ensuring that each patient receives the data she needs to have informed discussions with her physician to decide on the best treatment path, even years after her initial treatment.”

The original NSABP B-42 trial, designed to determine whether ELT improves DFS after a standard 5 years of aromatase inhibitor-based therapy, enrolled nearly 4,000 postmenopausal women with stage I-IIIA hormone receptor-positive breast cancer, who were disease-free after about 5 years of treatment with an aromatase inhibitor or tamoxifen followed by an aromatase inhibitor. The trial arms were randomly assigned to either receive 5 years of letrozole – an endocrine therapy used commonly in adjuvant settings – or a placebo. The trial showed a numerical DFS benefit of 3.3% at 10 years from ELT for the entire study cohort; however, no clinical features that indicated which women would achieve this benefit were identified in the trial. This led to the search for genomic biomarkers which could predict the benefit of ELT, and was the basis for this translational study.

“We are pleased to have contributed to the NSABP B-42 trial findings, with the important observation that genomic profiling with MammaPrint identifies the cohort most likely to benefit from ELT, and those who are unlikely to benefit,” said William Audeh, MD, Chief Medical Officer at Agendia. “These data will be of value to clinicians, and women with breast cancer, as they make the challenging decision as to whether to undertake an additional five years of endocrine therapy, a decision for which clinical features offered little guidance.”

At ASCO 2021, Agendia also presented additional data about the Ultra Low Risk threshold from the MINDACT study as well as a larger suite of data from the company’s groundbreaking FLEX registry, a large-scale, prospective, observational breast cancer study using whole transcriptome sequencing. FLEX enables true precision oncology by recruiting patients from various ethnicities, ages and genders representative of the total breast cancer population as part of an ongoing effort to increase representation of diverse populations and data in clinical trials.

About Agendia

Agendia is a precision oncology company headquartered in Irvine, California, committed to bringing patients with early stage breast cancer and their physicians the information they need to make the best decisions for the full treatment journey. The company currently offers two commercially-available genomic profiling tests, supported by the highest levels of clinical and real world evidence, that provide comprehensive genomic information that can be used to identify the most effective breast cancer treatment possible for each patient.

MammaPrint®, the 70-gene breast cancer recurrence assay, is the only FDA-cleared risk of recurrence test backed by peer-reviewed, prospective outcome data and inclusion in both national and international treatment guidelines. BluePrint®, the 80-gene molecular subtyping assay, is the only commercially-available test that evaluates the underlying biology of a tumor to determine what is driving its growth. Together, MammaPrint® and BluePrint® provide a comprehensive genomic profile to help physicians make more informed decisions in the pre- and post-operative treatment settings.

Agendia develops evidence-based novel genomic tests and forges partnerships with groundbreaking companies to develop next-generation digital treatment tools. The ongoing research builds an arsenal of data that improve patient outcomes and support the evolving clinical needs of patients with breast cancer and their physicians every step of the way, from initial diagnosis to cancer-free.

Agendia’s assays can be ordered on core biopsies or surgical specimens to inform pre- and post-operative treatment decisions. For more information on Agendia’s assays and ongoing trials, please visit www.agendia.com.