Experts Disagree on Value of A Genetic Test for Breast-Cancer Patients

By Jane Farrell

The American Society of Clinical Oncology (ASCO) recently updated its guideline on biomarkers with regard to the MammaPrint genetic test, concluding that in certain groups of breast-cancer patients, MammaPrint can better identify those who don’t require chemotherapy.

The update was published in the Journal of Clinical Oncology (JCO).

ASCO based its conclusion on results of a research project called the MINDACT study. The project is a collaboration among the Agendia medical-research company, which developed the MammaPrint test; the European Organization for Research and Treatment of Cancer (EORTC); and another research organization, the Breast International Group (BIG). Its results were published in 2016.

The MammaPrint test evaluates the activity of some genes during the early stages of breast cancer and is designed to predict the likelihood of recurrence in the ten years after diagnosis. The test results can be used in helping physicians and patients make decisions about treatment.

However, a group of authors from the German Institute for Quality and Efficiency in Health Care (IQWiG) has contradicted ASCO’s conclusion in a letter to the editor of the JCO: As the first prospective randomized controlled trial, they said, MINDACT provides valuable findings on biomarker tests. But the IQWiG authors believe that the conclusion drawn by the ASCO authors is incorrect.

The MINDACT study primarily aimed to answer the question of whether patients with a high recurrence risk according to conventional clinical criteria, but a low recurrence risk according to MammaPrint, could omit chemotherapy. However, in these patients an analysis showed a statistically significant disadvantage of the test for the outcome “disease-free survival.” Moreover, with an absolute risk difference of 3 percent after only five years, this difference reached a magnitude that had been defined as clinically relevant for other questions of MINDACT.

In addition, the IQWiG authors presented their own analysis of the published MINDACT data, which indicates that the MammaPrint test does not provide more information than conventional clinical criteria. However, original data from MINDACT would be required to verify this finding. In their response to IQWiG’s letter to the editor, the ASCO authors noted that IQWiG’s additional analysis was interesting and agreed that a more complete analysis of the MINDACT data would be useful if the original data could be obtained.