A recent phase III clinical trial, known as PARTIQoL, has demonstrated that proton beam therapy (PBT) and intensity modulated radiation therapy (IMRT) achieve equally high rates of tumor control in patients with low- and intermediate-risk prostate cancer. The study, presented at the American Society for Radiation Oncology (ASTRO) Annual Meeting, indicates no significant differences in patient-reported quality of life between the two advanced radiation therapies.
PARTIQoL Trial Details
The PARTIQoL trial, conducted between June 2012 and November 2021, involved 450 patients with localized prostate cancer across 29 recruiting centers. Patients were randomly assigned to receive either proton therapy or IMRT, without hormonal therapy. The median age of participants was 68 years, and the median follow-up period was 60.3 months. The primary endpoint focused on changes in bowel-related quality of life, while secondary endpoints included assessments of sexual and urinary functions, toxicity, and efficacy.
Key Findings on Quality of Life
Patient-reported outcomes regarding bowel, urinary, and sexual functions were collected via questionnaires at baseline and at multiple time points post-treatment. The results indicated no significant differences between the IMRT and proton therapy arms in any of the quality-of-life domains assessed. For instance, baseline bowel function scores were 93.7 for IMRT and 93.5 for proton therapy, with only minor, clinically insignificant declines observed after two years (91.8 and 91.9, respectively; p=0.836).
Progression-Free Survival
In terms of efficacy, the study found no statistically significant difference in progression-free survival between the two treatment groups. At five years post-treatment, 93.7% of patients treated with IMRT and 93.4% of those treated with protons had not experienced tumor progression (p=0.706). This suggests that both therapies are equally effective in controlling localized prostate cancer.
Expert Commentary
Dr. Jason Efstathiou, MD, PhD, FASTRO, principal investigator of the trial and vice chair of faculty and academic affairs in the department of radiation oncology at Massachusetts General Hospital, noted, "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."
He further added, "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."
Implications for Treatment Decisions
With approximately 70% of new prostate cancer cases diagnosed as localized disease, the findings from the PARTIQoL trial offer valuable insights for treatment planning. The study suggests that either IMRT or proton therapy can be considered as viable options, allowing clinicians to tailor treatment decisions based on factors such as cost, availability, and individual patient preferences. While proton therapy offers the theoretical advantage of reduced radiation exposure to surrounding healthy tissue, it is also associated with higher costs and limited availability compared to IMRT.
Ongoing Research
Dr. Efstathiou mentioned that further analyses are underway to identify potential subgroups of patients who may benefit more from one technology over the other. The study authors also emphasized that the trial focused exclusively on patients with localized prostate cancer, and the findings may not be generalizable to those with more advanced stages of the disease.
