A study modeling outcomes for women with estrogen receptor–positive, HER2-negative breast cancer indicates that those with the highest score on a clinicomolecular test would be most likely to benefit from chemotherapy to reduce the risk of distant recurrence.
The model, created by William Gradishar, MD, from the Robert H. Lurie Comprehensive Cancer Center in Chicago, and colleagues, uses validated 10-year risk of distant breast recurrences as a function of the EndoPredict (EPclin) 12-gene clinicomolecular assay score.
The model suggests that for patients with a low EPclin score, chemotherapy would offer no additional benefit over endocrine therapy, whereas those with high scores would have an increase in recurrence-free survival with chemotherapy.
“Overall, this demonstrates that EndoPredict provides guidance on the expected absolute benefit from adjuvant chemotherapy in addition to prognostic information for patients with ER-positive, HER2-negative early-stage breast cancer. Therefore, EndoPredict can identify patients likely to benefit sufficiently from adjuvant chemotherapy to justify associated toxicities,” Dr. Gradishar and associates wrote in.
The assay has previously been shown to accurately predict the risk of distant metastases in patients with estrogen receptor–positive, human epidermal growth factor receptor–2 negative (ER+/HER2–) breast cancer, but the ability to predict absolute benefit of chemotherapy is less clear, and it would be unethical to conduct a randomized trial with a no-chemotherapy arm, the investigators noted.
Instead, the investigators created a mathematical model to try to answer the question. They determined the average relative benefit of chemotherapy for reducing distant recurrence using a published meta-analysis from the Early Breast Cancer Trialists’ Collaborative Group, and they estimated absolute chemotherapy benefit differences across a range of interaction strengths between relative chemotherapy benefit and the EPclin score. Finally, they calculated average absolute benefit for patients with high and low EPclin scores using the distribution of scores in 2,185 samples tested by Myriad Genetics, maker of the assay.
They found that the average expected absolute benefit of chemotherapy treatment for patients with a low EPclin score was 1.8% assuming no interaction between prognostic factors and chemotherapy benefit, and 1.5% for maximal interaction, suggesting no significant added benefit from chemotherapy.
In contrast, for patients with a high EPclin score, the absolute benefit assuming no interaction was 5.3% and the benefit assuming maximal interaction was 7.3%.
“Overall, these data demonstrate that high EPclin scores are associated with maximal predicted chemotherapy benefit, and low EPclin scores are associated with no clinically meaningful benefit. This association is irrespective of interaction strength between EPclin and predicted chemotherapy benefit, and the impact of any interaction on absolute benefit is much smaller than the ability to accurately estimate absolute risk,” they wrote.
The study was supported by Myriad Genetics. Dr. Gradishar disclosed consulting or advisory roles with Genentech and Roche. Five of the coauthors are employees of Myriad Genetics or Myriad International.
SOURCE: Gradishar W et al. Precision Oncology. 2016 Aug. 6.