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Comment & Response
August 5, 2021

Single-Dose Radiotherapy for Prostate Cancer—Lessons Learned From Single-Fraction High-Dose-Rate Brachytherapy—Reply

Author Affiliations
  • 1Champalimaud Centre for the Unknown, Lisbon, Portugal
  • 2Memorial Sloan Kettering Cancer Center, New York, New York
JAMA Oncol. 2021;7(10):1573. doi:10.1001/jamaoncol.2021.2694

In Reply Squires and Krauss provide a critique of our proof-of-principle phase 2 randomized PROSINT study,1 cautioning against early conclusions relative to the use of 24-Gy single-dose radiotherapy (SDRT) as a possible standard of care in prostate cancer radiotherapy. They argue that the 4-year biochemical control rate of the PROSINT 24-Gy SDRT (77%) is similar to the 73.5% 5-year rate reported after 19-Gy high-dose-rate (HDR) single-fraction brachytherapy (SFBT).2 They also suggest that the dose inhomogeneity and mean dose with 19-Gy SFBT and 24-Gy SDRT are similar. However, dose painting was used meticulously in SDRT to conformally avoid normal organs at risk, unlike with HDR brachytherapy. Furthermore, the PROSINT study exclusively accrued patients with National Comprehensive Cancer Network intermediate-risk disease, unlike the SFBT study,2 which also included patients with low-risk disease (24%) and had a remarkably low component of unfavorable intermediate-risk phenotypes (30%, vs 68% in PROSINT).1 Importantly, while relapses occurred with similar rates in all risk categories following SFBT,2 none of the patients with favorable intermediate-risk disease in the PROSINT trial1 had a biochemical relapse in either arm of the study, whose prostate-specific antigen kinetics were strikingly similar, corroborating the notion of similar biological equivalence. Furthermore, gallium 68 prostate-specific membrane antigen scans in all prostate-specific antigen–relapsing patients post-SDRT detected only 1 intraprostatic tracer-avid lesion, biopsy proven as local recurrence.

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