Controlled burn.

The FLAME trial found that an MR-guided simultaneous integrated boost (SIB) of 95 Gy in 35 fractions improved biochemical control without increasing toxicity in men treated for intermediate and high risk prostate cancer. While there was no difference in rectal toxicity between arms, this secondary analysis of FLAME sought to determine if the minimum dose to 2cc and to 50% of the anorectum were associated with late grade 2+ toxicity. The short answer is yes. Increasing D2cc and D50% are associated with increased risk of toxicity. But, because constraints to organs at risk were prioritized over SIB coverage, there was basically no difference in either D2cc (73 Gy) or D50% (36Gy) between arms. In other words, focal dose-escalation that strictly respects anorectal constraints should indeed increase biochemical control rates without increasing toxicity. | Groen, Radiother Oncol 2021