The Role of Invasive Disease-Free Survival in Breast Cancer Research

In an interview with Targeted Oncology, Stephanie L. Graff, MD, FACP, FASCO, director of the Breast Oncology Program at Brown University Health Cancer Institute, and co-leader of the Breast Cancer Translational Research Disease Group, discusses the feasability of invasive disease-free survival (iDFS) as a surrogate end point in breast cancer trials.

In the complex world of clinical trials for breast cancer, choosing the right metric to measure success is critical. While overall survival—the length of time a patient lives after diagnosis—is often considered the gold standard, it presents a unique challenge, especially for patients with hormone receptor-positive (HR+) metastatic breast cancer. This particular form of breast cancer is known for being a "long game." Patients with an HR+ diagnosis frequently undergo multiple lines of therapy and can live for many years with their disease. Relying solely on overall survival as a primary endpoint would mean that clinical trials would have to extend for many years, delaying the approval of potentially life-saving drugs for patients who need them now.

This is where a different metric, iDFS, becomes a reasonable and powerful surrogate endpoint. iDFS measures the length of time a patient lives without the disease returning after treatment. By using iDFS as the primary endpoint in clinical trials, researchers can get a much faster read on the effectiveness of a new therapy. This accelerated process allows promising treatments to be delivered to higher-risk patients much earlier, potentially making a meaningful difference in their quality of life and health during those critical intervening years.

The push for using these surrogate end points is not just a scientific preference; it's a movement with deep roots in patient advocacy. For decades, patient advocates have fought in courts and at hearings for earlier access to new therapies. They understand that waiting years for overall survival data can mean the difference between life and death for someone currently battling the disease. While regulators require long-term follow-up to be included as a secondary end point in these trials, the use of iDFS as a primary measure respects the urgency felt by the patient community. The hope is that successful outcomes in iDFS will eventually translate into a significant improvement in overall survival. If they don't, the enthusiasm for a particular therapy will naturally wane, but for now, this approach offers a faster, more effective way to bring much-needed innovation to the forefront of breast cancer care.