Focal Boost to the Intraprostatic Tumor in External Beam Radiotherapy for Patients With Localized Prostate Cancer: 10-Year Outcomes of the FLAME Trial

The FLAME trial hypothesized that focal boosting of intraprostatic tumor lesion(s) in addition to standard external beam radiotherapy (EBRT) improves biochemical disease-free survival (bDFS). In this multicenter randomized phase III trial, patients with intermediate- and high-risk prostate cancer (PCa) were assigned to the standard (EBRT of 77 Gy in 35 fractions to the whole prostate gland) or focal boost arm (standard EBRT with a focal boost of up to 95 Gy to magnetic resonance imaging-visible lesion(s)). Initial 5-year results showed a significant improvement in the focal boost arm for bDFS without additional toxicity. Here, we report bDFS, disease-free survival (DFS), local DFS, regional lymph node DFS, distant metastasis-free survival (DMFS), and overall survival (OS) after a 10-year follow-up. Dose-response curves were created using the dose heterogeneity in the study arm. Between 2009 and 2015, 571 patients were randomly assigned. The 10-year bDFS was 71% in the standard arm versus 86% in the focal boost arm. A significant improvement was also observed for other end points, except DMFS and OS. However, the dose-response curve suggests an association between dose and distant metastatic failure. The 10-year results demonstrated the sustained benefit of focal boosting on bDFS. By preventing biochemical failure, men are spared the potential burden of PCa recurrence.