Patient-reported quality of life (QoL) was similar between proton beam therapy (PBT) and intensity-modulated radiation therapy (IMRT) among men with localized prostate cancer, the randomized PARTIQoL trial showed.

At 24 months, the mean change in bowel function scores was -2.4 in the PBT group versus -2.2 in the IMRT group (P=0.84), reported Jason A. Efstathiou, MD, of Massachusetts General Hospital in Boston, during a press briefing at the American Society for Radiation Oncology annual meeting in Washington, D.C.

QoL scores for urinary irritation (P=0.85) and urinary incontinence (P=0.99) were also similar between the two groups, and the mean change in sexual function score at 24 months was -10.6 with PBT and -6.0 with IMRT (P=0.05).

Furthermore, there was no statistically significant difference in progression-free survival rates between the PBT and IMRT groups: 98.1% versus 99% at 24 months and 93.4% versus 93.7% at 60 months.

“IMRT and proton therapy offer patients with localized prostate cancer equally excellent quality-of-life outcomes with highly effective tumor control, without measurable differences between the two approaches,” Efstathiou said.

Sameer Keole, MD, of the Mayo Clinic in Scottsdale, Arizona, who moderated the press briefing, noted that “for me, as a practicing radiation oncologist who does treatments for prostate cancer and has access to both protons and IMRT, I think this is a tremendous study. It really shows us that we have two great options.”

“The take-home point is that these control rates are phenomenal, and the complication rates were very, very low,” he added. “Men can go seek definitive treatment with a radiation oncologist and know that external radiation beam therapy, whether with proton beam therapy or IMRT, is an excellent treatment option when it is appropriate.”

PARTIQoL is a phase III trial that randomized 450 men with low- or intermediate-risk prostate cancer across 30 centers from June 2012 to November 2021. Of these men, 167 in the PBT group and 162 in the IMRT group completed a bowel QoL assessment at 24 months.

Median age was 68 years, 79-82% were white, and 12-13% were Black. Fifty-nine percent had intermediate-risk disease, 51% received hypofractionation, and 48% used a rectal spacer; 49% of PBT patients were treated with pencil beam scanning.

QoL was assessed with the 100-point Expanded Prostate Cancer Index Composite tool.

In subgroup analyses, there was no difference in bowel QoL scores by age group (≤65 years vs >65 years), disease risk (intermediate or low), rectal spacer use, or fractionation schedule (conventional or hypofractionation).

“Our study was limited to [patients with] localized low- and intermediate-risk prostate cancer receiving either conventionally or moderately hypofractionated therapy,” Efstathiou acknowledged. “Our study did not address higher-risk disease, nodal therapy, use of hormonal therapy or other systemic therapy, local recurrence, or retreatment scenarios. And both proton therapy and IMRT continue to evolve. There’s a lot of ongoing work to optimize delivery … and practice is evolving toward ultra-hypofractionation and other techniques.”

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