Final fossa.

Top Line: What is the ideal dose to the prostate fossa when delivering salvage radiation?

The Study: In SAKK 09/10, 350 men with biochemical recurrence after radical prostatectomy were randomized to receive 64 Gy in 32 fractions or 70 Gy in 35 fractions to the prostate fossa. To be included, they had to have a lowest post-RP PSA < 0.4 with two subsequent rises to a level > 0.1 but ≤ 2. The median PSA was 0.3, and 75% had PSA ≤ 0.5. The target was the fossa only with no nodal coverage as all patients had to be node negative using either CT (65%) or MRI (35%) before treatment. PTV dose was prescribed to median (D50%) with +7%/-5% heterogeneity. The full bladder wall and empty rectal wall were used as OARs with objectives of rectal wall V70<20% and V60<50%, bladder wall V65<50%, and femoral head V50<10%. The primary outcome, freedom from biochemical progression (FFBP) was defined as any PSA after treatment of 0.4 or higher and rising. This is important to note as there is great variation in how to define second biochemical progression after salvage RT. As previously reported in abstract form, there was no difference in median FFBP (8.2y @ 64 Gy, 7.6y @ 70 Gy) or the rate of FFBP at 6 years (62% vs 61%). There was no difference in the rate of late grade 2+ GU toxicity, but there was a significant increase in late grade 2+ GI toxicity with 70 Gy (22.3% vs 11.5%). Patient-reported quality of life metrics were no different between arms.

TBL: When delivering salvage prostate fossa radiation with no visible gross disease, SAKK 09/10 found that dose escalation from 64 to 70 Gy does not reduce the rate of subsequent biochemical progression and increases the rate of late grade 2 GI toxicity. | Ghadjar, Eur Urol 2021