Top Line: Does ultra-hypofractionated prostate radiation cause more toxicity than moderate hypofractionation?
The Study: This British Columbian phase 2 trial randomized 78 evaluable men with intermediate (n=53) or high (n=25) risk prostate cancer to moderate (70 Gy in 28 daily fractions) versus ultra (36.25 Gy in 5 weekly fractions) hypofractionation (UHF). The 70/28 technique was analogous to RTOG 0415. In both arms, the CTV consisted of the prostate and proximal 1cm of the seminal vesicles (1-2cm for high risk). In the UHF arm, a uniform 4mm PTV margin was used, and treatment was delivered using VMAT with 1 or 2 arcs. The max dose in the PTV was limited to 105% and 95% of the PTV received at least 99% of the prescribed dose. The primary outcome of incidence of grade 3+ toxicity at 6 months was no worse—and, in fact, was numerically better—with ultra (2%) than with moderate (8%) hypofractionation. Same goes for grade 2+ toxicity which was 24% v 36%. Similarly, there were no significant differences in measured quality of life outcomes. What’s unique about this trial is the enrollees were particularly elder (median age 74) with notable bladder outlet symptoms (median IPSS 9), yet ultra-hypofractionation still appears quite safe even in this vulnerable population. Finally, we applaud the authors for not stopping here but following up “with a province-wide registry so that ultra-hypofractionation can be prescribed in a relatively uniform manner and toxicity and disease control outcomes can be captured systematically.”
TBL: Ultra-hypofractionation, this time delivered over five weekly fractions, for definitive treatment of intermediate to high risk prostate cancer appears yet again to be exceedingly well tolerated. | Kwan, Int J Radiat Oncol Biol Phys 2022