Proton therapy, IMRT comparably effective for low-, intermediate-risk prostate cancer
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Key takeaways:
- Men with low- or intermediate-risk prostate cancer achieved similar quality-of-life outcomes whether they underwent proton therapy or IMRT.
- PFS results did not differ between treatments.
Photon and proton beam radiation therapies conferred similar outcomes for men with localized prostate cancer, according to results of a randomized phase 3 trial.
Researchers did not observe any differences in PFS or quality-of-life measurements between men who underwent proton therapy or intensity-modulated radiation therapy, findings presented at American Society for Radiation Oncology Annual Meeting showed.
“We can use either of these tools with comparably excellent outcomes,” Jason Efstathiou, MD, PhD, FASTRO, vice chair of faculty and academic affairs in the department of radiation oncology at Massachusetts General Hospital, as well as professor of radiation oncology at Harvard Medical School, said in a press release. “There have been so many advances in the delivery of contemporary radiation — such as the incorporation of scanned and modulated beams and in-room imaging — that I think the potential gaps between these technologies have narrowed over time.”
Background and methods
An estimated 299,010 new cases of prostate cancer will be diagnosed in the United States this year, according to American Cancer Society estimates.
Approximately 70% of prostate cancer cases are diagnosed as localized disease, according to study background.
Many men with prostate cancer undergo external beam radiation; however, there are different types.
Photon therapy — such as intensity-modulated radiation therapy — delivers X-ray dose radiation to the tumor, but it can affect nearby organs and cause adverse events.
Proton therapy provides more precise treatment of cancer cells, but it costs substantially more and fewer medical institutions offer it.
“Patients now have many options for how they might manage their prostate cancer, but trying to sift through all of the information to understand the consequences for their quality of life can be confusing,” Efstathiou said. “To aid them in making these decisions, we compared two of the most advanced forms of external beam radiation — IMRT and proton beam therapy — head to head.”
Efstathiou and colleagues randomly assigned 450 men with low- or intermediate-risk prostate cancer (median age, 68 years; range, 46-89; 59% intermediate risk) to receive IMRT or proton beam therapy. The men underwent treatment at one of 29 centers between June 2012 and November 2021.
Change in bowel quality of life at 24 months served as the primary endpoint. Urinary and sexual functions, toxicities and efficacy served as secondary endpoints.
Results and next steps
After median follow-up of 60.3 months, results showed comparable quality-of-life outcomes in both treatment groups.
Mean bowel function scores decreased approximately 2% in both groups after 2 years, a decline researchers characterized as not clinically meaningful. Bowel function scores remained similar at various time points throughout the study.
Investigators observed no difference in urinary incontinence, urinary irritation or sexual function between groups.
Results also showed similar rates of 60-month PFS in the proton therapy and IMRT cohorts (93.4% vs. 93.7%; HR = 1.16; 95% CI, 0.53-2.57).
Results appeared comparable in subgroups based on age, low-risk or intermediate-risk disease, fractional schedule and rectal spacer use.
“There may be subgroups that benefit from one technology over another, and we’re actively continuing analyses of that,” Efstathiou said.
During a press briefing, Efstathiou acknowledged study limitations. Researchers did not evaluate men with higher-risk prostate cancer, nor did they examine effects of nodal therapy, or use of hormonal or systemic therapies.
Future studies could compare proton beam therapy and IMRT based on those factors.
“This is a tremendous study. I think it really shows us we have two great options,” ASTRO President-elect Sameer R. Keole, MD, FASTRO, radiation oncologist at Mayo Clinic, said during a press briefing. “These control rates are phenomenal, and the complication rates were very, very low. I think men can go seek definitive treatment when it's appropriate with a radiation oncologist and know that external beam radiation, whether it’s proton therapy or IMRT, is an excellent treatment option.”
References:
- ASTRO. IMRT and proton therapy offer equally high quality of life and tumor control for people with prostate cancer (press release). Published Sept. 30, 2024. Accessed Sept. 30, 2024.
- Efstathiou JA, et al. Abstract LBA 01. Presented at: ASTRO Annual Meeting; Sept. 29-Oct. 2, 2024; Washington, D.C.
Perspective
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Steven J. Frank, MD
The authors should be congratulated for running this phase 3 trial and providing level one evidence on the excellent outcomes of radiation therapy with proton therapy for men diagnosed with early-stage prostate cancer. Patients with early-stage prostate cancer have high cure rates with excellent urinary, bowel and sexual function. Men with early-stage prostate cancer have multiple radiation therapy options that will provide them high cure rates with excellent quality of life. The role of proton therapy for patients with more advanced disease in combination with androgen deprivation therapy, brachytherapy and metastatic disease to the lymph nodes are exciting areas of further study with intensity-modulated proton therapy and stereotactic body proton therapy. At MD Anderson, we are utilizing the most advanced technologies in proton therapy to continue to address these exciting questions to improve the outcomes for people with cancer.
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Efstathiou JA, et al. Abstract LBA 01. Presented at: ASTRO Annual Meeting; Sept. 29-Oct. 2, 2024; Washington, D.C.
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