Hypofractionated radiotherapy an ‘acceptable practice standard’ after prostatectomy
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Men who underwent hypofractionated radiotherapy after prostatectomy achieved comparable safety and quality-of-life outcomes as men who received a conventional regimen, according to study results.
Men assigned the hypofractionated regimen reported more gastrointestinal toxicity upon completion of radiotherapy.
However, the hypofractionated regimen appeared noninferior to conventional radiotherapy with regard to patient-reported GI and genitourinary toxicity at 2 years, results of the phase 3 NRG Oncology GU003 trial presented at American Society for Radiation Oncology Annual Meeting showed.
Longer follow-up is necessary to assess disease control endpoints.
“Hypofractionated postprostatectomy radiotherapy is a new acceptable practice standard [for this patient population],” Mark K. Buyyounouski, MD, professor of radiation oncology and director of genitourinary cancers at Stanford University’s School of Medicine, said during the presentation.
Approximately 98% of men diagnosed with prostate cancer live at least a decade after treatment, according to study background. Consequently, long-term adverse effects and strategies to ensure quality of life are key considerations.
Hypofractionated radiation therapy — which consists of fewer fractions of radiation but higher doses per fraction — is “a well-accepted practice standard” for men who do not undergo prostatectomy, Buyyounouski said.
The NRG Oncology GU003 trial — conducted at more than 90 centers in North America — was the first to assess whether hypofractionated postprostatectomy could be a viable option for men who underwent prostatectomy and required radiotherapy due to rising PSA levels, indicating their cancer had returned.
Buyyounouski and colleagues aimed to determine if postprostatectomy hypofractionated radiotherapy — delivered over 5 weeks — resulted in increased patient-reported genitourinary or GI toxicity compared with conventionally fractionated postoperative radiotherapy, delivered over 7 weeks.
“Preserving quality of life was a major priority when testing the shorter treatment course,” Buyyounouski said in a press release. “It is important for patients to know that accepting a more convenient treatment doesn’t mean they have to compromise on quality of life.”
The trial — conducted between July 2017 and July 2018 — included 296 men who met one of two criteria: undetectable PSA (< 0.1 ng/mL) with either margin-negative pT3pN0/X or margin-positive pT2pN0/X adenocarcinoma of the prostate, or detectable PSA ( 0.1 ng/mL) and pT2/3pN0/X disease.
Researchers stratified men by baseline Expanded Prostate Cancer Index Composite (EPIC) scores and whether they had received androgen deprivation therapy within the prior 6 months.
They randomly assigned 144 men to hypofractionated radiotherapy, which consisted of 62.5 Gy to the prostate bed administered in 25 fractions of 2.5 Gy. The other 152 men received conventional radiotherapy, which consisted of 66.6 Gy administered in 37 fractions of 1.8 Gy.
Study protocol excluded men who had received lymph node radiotherapy.
Change scores — defined as 24-month score minus baseline score — in the EPIC genitourinary and GI domains served as co-primary endpoints.
Results showed no statistically significant or clinically meaningful difference in mean genitourinary change score from baseline to any of the four predetermined assessment points — end of radiotherapy, 6 months, 12 months or 24 months.
Results showed a statistically significant difference in mean GI change score from baseline to end of radiotherapy between the hypofractionated and conventional radiotherapy groups (mean, –15 vs. –6.8; P .01). However, results showed no significant differences in mean GI change scores between baseline and 6 months, 12 months or 24 months.
“Short-term side effects of radiation therapy are well-established, and patients understand that,” Buyyounouski said in the release. “What patients ultimately want to know is whether the side effects will go away, and that's what we saw in our study. There was some increase in bowel side effects — more so with the shorter treatment — but, after 6 months, these side effects resolved, and patients didn’t report any further or additional bowel or bladder side effects 1 and 2 years later.”
Based on the results, it may be possible to adjust treatment techniques to reduce the GI symptoms patients reported at the end of treatment, Buyyounouski said.
Median follow-up for censored patients was 2.1 years. At that time, researchers reported no difference between the hypofractionated and conventional radiotherapy groups with regard to local failure (2-year actuarial, 0.7% vs. 0.8%) or biochemical failure (2-year actuarial, 12% vs. 8%).
“Delivering postprostatectomy radiation therapy with fewer treatments is a win when it comes to reducing the burden of prostate cancer on society,” Buyyounouski said. “For patients, fewer treatments equate to a shorter time commitment that increases access to a potentially curative treatment, reduces expenses related to travel and co-pays, and involves less time away from work and other responsibilities. Additionally, providers can improve their facility’s productivity and increase the overall capacity for all patients. And for payors, fewer treatments mean fewer expenses.”
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Buyyounouski MK, et al. Abstract 3. Presented at ASTRO Annual Meeting; Oct. 24-27, 2021; Chicago.
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