Two types of contemporary radiation therapy—proton-beam therapy or intensity-modulated radiation therapy—may provide comparable rates of tumor control with no differences in patient-reported quality of life among patients with low- and intermediate-risk prostate cancer, according to new findings presented by Efstathiou et al at the 2024 American Society for Radiation Oncology (ASTRO) Annual Meeting (Abstract LBA01) and simultaneously published in the International Journal of Radiation Oncology • Biology • Physics.
Background
About 70% of new prostate cancer diagnoses, representing over 200,000 U.S. patients per year, are localized disease. Patients diagnosed with localized prostate cancer typically have many treatment options, and since many of them will survive and live many years posttreatment, their quality of life becomes particularly important when making treatment decisions.
External-beam radiation therapy is a common treatment option in patients with localized prostate cancer. Most types of this therapy use photon beams, the same radiation used in lower doses for x-rays. Photon beams can reach tumors deep inside the body but scatter bits of radiation along the way, potentially leading to side effects in the area treated. Intensity-modulated radiation therapy is an advanced type of photon-based radiation that allows oncologists to shape and modulate the radiation beams to conform to the three-dimensional shape of the tumor.
Proton therapy is another external-beam option that uses protons rather than photon beams. These charged particles are designed to cancer by producing a sudden burst of energy once they stop inside the tumor. Because this release happens directly at the tumor site, protons deliver less radiation along their path and are potentially less likely to harm surrounding healthy tissue. However, this increased precision often comes with significantly higher costs, and the specialized equipment and facilities required for proton therapy are less widely available compared with those required for intensity-modulated radiation therapy.
Jason Efstathiou, MD, PhD, FASTRO
“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,” explained lead study author Jason Efstathiou, MD, PhD, FASTRO, Professor of Radiation Oncology at Harvard Medical School and Vice Chair of Faculty and Academic Affairs in the Department of Radiation Oncology at Massachusetts General Hospital. “To aid them in making these decisions, we compared two of the most advanced [types] of external-beam radiation, [intensity-modulated radiation therapy] and proton-beam therapy, head to head,” he added.
Study Methods and Results
In the new phase III PARTIQoL clinical trial, researchers randomly assigned 450 patients with a median age of 68 years who had low- or intermediate-risk localized prostate cancer to receive either proton-beam therapy or intensity-modulated radiation therapy without hormonal therapy. Between June 2012 and November 2021. The median age was 68 years old. The patients were asked to self-report bowel, urinary, and sexual functions via questionnaires at baseline and at multiple time points following treatment.
After a median follow-up of 60.3 months, the researchers found no statistically significant differences for any of the quality-of-life domains at any time point between the proton beam therapy and intensity-modulated radiation therapy groups. The patients treated with either technique reported just small, clinically insignificant declines from baseline levels. For instance, compared with those in the proton-beam therapy group, the patients in the intensity-modulated radiation therapy group reported average bowel function scores of 93.7 vs 93.5/100 at baseline and 91.8 vs 91.9 after 2 years—showing a decrease of roughly 2% for each treatment group (P = .836).
Further, 5 years posttreatment, 93.7% of the patients who received intensity-modulated radiation therapy and 93.4% of those who received proton-beam therapy experienced progression-free survival (P = .706).
“We can use either of these tools with comparably excellent outcomes. 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,” suggested Dr. Efstathiou.
The researchers also discovered no sustained differences in quality of life or survival between both treatment groups for any predefined subgroups: low- vs intermediate-risk disease, older vs younger than 65 years, rectal spacer use vs no rectal spacer use, and shortened vs conventional fractionation schedule.
Conclusions
“We tested two contemporary, advanced forms of external-beam radiation for a very common cancer, and we demonstrated that both are very safe, effective treatments that give patients excellent outcomes in terms of quality of life and cancer control,” Dr. Efstathiou highlighted.
The completion of the trial was considered significant for the field, which relies on advanced technologies that can be difficult to assess in a randomized controlled trial. Despite the findings, the researchers are continuing to analyze the data set and hope to examine outcomes in patients with more advanced prostate cancer.
“There may be subgroups that benefit from one technology over another, and we’re actively continuing analyses of that,” Dr. Efstathiou noted. “Providing the best evidence-based care calls for rigorously testing the tools we use for that care. We commonly use randomized controlled trials to evaluate new drugs, for example, but not necessarily for new technologies. I hope that our work shows that randomized, controlled trials are critical in technology assessment,” he concluded.
Disclosure: The research in this study was funded in part by the Prostate Cancer Foundation. For full disclosures of the study authors, visit astro2024.eventscribe.net and redjournal.org.
