Top Line: What is the risk of late toxicity following hypofractionated post-prostatectomy radiation?
The Study: Early outcomes from RTOG GU003 showed slightly more GI toxicity with hypofractionation at the end of treatment, but no difference in toxicity at 6 months and out to 2 years. However, there has been caution in widely adopting the 62.5 Gy in 25 fractions regimen without longer follow up. Some of the data supporting the GU003 regimen was from the University of Wisconsin. Between 2003 and 2013, 161 patients with biochemical recurrence of prostate cancer were treated with mostly 65 Gy in 26 fractions (95.6%) to the prostate fossa. The other 4.4% received higher total doses (67.5-70 Gy), and 12.4% received elective nodal irradiation. Here, the authors report long-term toxicity outcomes for this cohort. The rate of late grade 3+ toxicity was 27.3%, and the median time to developing grade 3+ toxicity was a whopping 106 months. Most of the late toxicity events were GU in origin. While the rate of grade 3+ toxicity was just 2% at 2 years, it steadily rose to 9% at 5 years, 21% at 10 years, and 34% at 15 years.
TBL: “With 161 patients analyzed and over 13 years of follow-up, HYPORT employing 26 fractions of 2.5 Gy resulted in a higher-than-anticipated rate of severe late GU toxicities at very late time points.” | Ranta, Int J Radiat Oncol Biol Phys 2025
The Study: Early outcomes from RTOG GU003 showed slightly more GI toxicity with hypofractionation at the end of treatment, but no difference in toxicity at 6 months and out to 2 years. However, there has been caution in widely adopting the 62.5 Gy in 25 fractions regimen without longer follow up. Some of the data supporting the GU003 regimen was from the University of Wisconsin. Between 2003 and 2013, 161 patients with biochemical recurrence of prostate cancer were treated with mostly 65 Gy in 26 fractions (95.6%) to the prostate fossa. The other 4.4% received higher total doses (67.5-70 Gy), and 12.4% received elective nodal irradiation. Here, the authors report long-term toxicity outcomes for this cohort. The rate of late grade 3+ toxicity was 27.3%, and the median time to developing grade 3+ toxicity was a whopping 106 months. Most of the late toxicity events were GU in origin. While the rate of grade 3+ toxicity was just 2% at 2 years, it steadily rose to 9% at 5 years, 21% at 10 years, and 34% at 15 years.
TBL: “With 161 patients analyzed and over 13 years of follow-up, HYPORT employing 26 fractions of 2.5 Gy resulted in a higher-than-anticipated rate of severe late GU toxicities at very late time points.” | Ranta, Int J Radiat Oncol Biol Phys 2025