Hypofractionated prostate RT does not increase toxicity vs conventional RT

Hypofractionated postoperative prostate bed radiotherapy (HYPORT) did not increase patient-reported genitourinary (GU) or gastrointestinal toxicity (GI) compared with conventional postprostatectomy radiotherapy (COPORT), according to findings of a phase 3 clinical trial.^1,2

The results were reported at the 2021 American Society for Radiation Oncology Annual Meeting in Chicago, Illinois.

Mark Buyyounouski, MD

“NRG-GU003 is the first trial comparing a short course [of radiotherapy] to a well-established practice standard of 7 weeks. After 2 years, patients reported no increase in urinary or bowel side effects with the shorter course and its effectiveness was comparable,” said lead investigator Mark Buyyounouski, MD, of Stanford University, Palo Alto, California, in a news release.

The phase 3 trial included men with undetectable prostate-specific antigen (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.

HYPORT was administered to the prostate bed in 25 fractions of 2.5 Gy (62.25 Gy), and COPORT was administered in 37 fractions of 1.8 Gy (66.6 Gy). The GU and GI domains of the Expanded Prostate Cancer Index Composite (EPIC) were used to assess inferiority or noninferiority at 2 years after treatment. Secondary end points included patient-reported GI and GU symptoms at 6, 12, 24, and 60 months from the end of treatment, time to progression, freedom from biochemical failure, local failure, regional failure, salvage therapy, distant metastasis, death from prostate cancer, and overall survival rates, and adverse events, according to the news release.

A total of 296 men were randomized for the trial; 144 received HYPORT and 152 received COPORT. The investigators reported that compliance with EPIC was 100% at baseline, 83% at the end of radiotherapy, 77% at 6 months, 78% at 12 months, and 73% at 24 months.

At the end of radiotherapy treatment, HYPORT and COPORT mean GU change scores were neither clinically significant nor statistically significantly different. They remained this way at 6 and 12 months after treatment. Mean GI change scores were both clinically significant and statistically significantly different at the end of treatment (HYPORT mean GI = -15.0 vs COPORT mean GI = -6.8, P ≤ .01); however, these differences were resolved by 6 and 12 months after treatment. The 24-month mean GU and GI change scores for both forms of radiotherapy were neither clinically nor statistically significant (HYPORT mean GU= -5.2 vs COPORT mean GU= -3.0, P = 0.81; HYPORT mean GI= -2.2 vs COPORT mean GI= -1.5, P = 0.12). At 2.1-year median follow-up for censored patients, there was no difference between the treatment groups for biochemical failure defined as PSA ≥ 0.4 ng/mL followed by a value higher than the first by any amount (2-yr rate, 12% vs 8%, P =.29) or local failure (2-yr rate, 0.7% vs 0.8%, P = .35).

“Radiotherapy is a highly effective treatment after surgery if an elevated PSA indicates recurrence of disease. However, a small minority of men receive treatment. We hope these results will better allow patients access to treatment and ultimately reduce the burden of prostate cancer because a safe and shorter treatment is available,” Buyyounouski said in the news release.

References

1. Buyyounouski MK, Pugh SL, Chen RC, et al. Primary endpoint analysis of a randomized phase iii trial hypofractionated versus conventional post-prostatectomy radiotherapy NRG Oncology GU003. Paper presented at: 2021 American Society for Radiation Oncology Annual Meeting; October 24-27; Chicago, Illinois. Abstract 3

2. Hypofractionated post-operative prostate bed radiotherapy does not increase patient-reported toxicity for men with prostate cancer. News release. NRG Oncology. October 25, 2021. Accessed October 28, 2021. https://www.nrgoncology.org/Home/News/Post/hypofractionated-post-operative-prostate-bed-radiotherapy-does-not-increase-patient-reported-toxicity-for-men-with-prostate-cancer