Prostate Radiotherapy
MRI-Guided Focal Boost for Prostate Cancer: 10-Year FLAME Results
The randomized FLAME trial found durable improvement in biochemical disease-free survival when MRI-visible prostate tumors received a focused radiation boost.
Short answer: In the randomized FLAME trial, adding a focused radiation boost to the MRI-visible prostate tumor improved long-term PSA-based disease control. At 10 years, biochemical disease-free survival was 86% with the boost and 71% with standard treatment. The study did not show that the boost lengthened overall survival.
What did FLAME test?
FLAME enrolled 571 people with intermediate- or predominantly high-risk localized prostate cancer. Everyone received external-beam radiation to the whole prostate. Half were assigned an additional simultaneous boost of up to 95 Gy to the tumor visible on multiparametric MRI.
The plan was isotoxic: protecting the rectum, bladder, and other normal tissue took priority over delivering the maximum boost. That safety principle is central to applying the result.
What changed after 10 years?
The focal-boost group continued to have fewer biochemical failures:
- 86% were free from biochemical disease failure at 10 years with focal boost.
- 71% were free from biochemical disease failure with standard treatment.
Other disease-control endpoints improved, but distant-metastasis-free survival and overall survival did not differ significantly. Better PSA control can reduce the burden of recurrence testing and treatment, yet it should not be described as a proven survival benefit.
How does MRI guide treatment?
Multiparametric MRI helps identify a dominant lesion inside the prostate. The radiation plan then shapes a higher dose around that target while respecting normal-tissue limits. Image guidance is still needed at each treatment because the prostate and nearby organs can move.
MRI visibility is not perfect. Some cancers are multifocal, difficult to define, or close to sensitive structures. A focal boost supplements whole-gland treatment; it does not treat only the visible spot.
What do newer recommendations add?
In 2026, ESTRO published practical consensus recommendations for implementing focal boost with external-beam radiation or brachytherapy. The guidance addresses imaging, contouring, dose, quality assurance, and prioritization of organs at risk.
The phase 2 hypo-FLAME study also reported encouraging five-year control using five weekly SBRT treatments with a focal boost. Because it was not randomized, it supports feasibility rather than proving that boosted SBRT is superior.
Questions to discuss
Ask whether your risk group resembles the FLAME population, whether MRI shows a boostable lesion, how hormone therapy fits the plan, and which normal-tissue constraints could limit the boost. A focal boost is a planning strategy for selected patients—not a separate cure or a reason to compromise safety.
Questions patients often ask
What is a focal boost?
It is an additional radiation dose directed to the dominant tumor visible inside the prostate while the whole prostate still receives treatment.
Did focal boost improve survival?
It improved biochemical disease-free survival, but the reported 10-year analysis did not show a significant overall-survival or distant-metastasis-free-survival improvement.
Can every prostate tumor receive a focal boost?
No. The tumor must be defined reliably, and bladder, rectum, urethra, and other normal-tissue limits may prevent delivery of the full intended boost.
Sources and further reading
- Focal Boost to the Intraprostatic Tumor: 10-Year Outcomes of the FLAME Trial. Journal of Clinical Oncology (2025).
- How to focal boost in prostate cancer radiotherapy: ESTRO clinical practice consensus recommendations. Radiotherapy and Oncology (2026).
- Five-year efficacy and toxicity in the hypo-FLAME trial. Radiotherapy and Oncology (2024).
