BOSTON—Patients undergoing treatment for prostate cancer (PCa) using proton beam therapy report a higher quality of life (QOL) in early follow-up compared with patients treated with other radiation modalities, according to a new study presented at the American Society for Radiation Oncology annual meeting.

The two-year non-randomized study of 370 patients evaluated the adverse effects of proton beam therapy, 3D conformal radiotherapy (3D-CRT), and intensity modulated radiotherapy (IMRT). Ninety-four patients received proton beam therapy, 123 were treated with 3D-CRT, and 153 underwent IMRT.

At the first follow-up visit (two to three months after the start of treatment), patients who had 3D-CRT and IMRT experienced modest yet significant problems with bowel function, but those in the proton group had only minimal bowel problems, reported the study’s first author Phillip Gray, MD, a resident in the Harvard Radiation Oncology Program in Boston. The 3D-CRT and IMRT patients also reported modest yet significant urinary problems at first follow-up, but patients treated with proton therapy did not report similar problems until 12 months after treatment. Two years after treatment, patients undergoing all three forms of radiotherapy reported no significant problems with urination and similar problems with bowel function. Patients in all three treatment groups reported steadily worsening sexual function during the study period.

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The median patient age was 64 years for those receiving proton therapy, 70 for those receiving 3D-CRT, and 69 for those receiving IMRT. The treatment dose range was 74-82 Gy RBE for proton therapy, 66.4-79.2 Gy for 3D-CRT, and 75.6-79.2 Gy for IMRT. Lower doses given to the 3D-CRT group were thought to possibly explain some of the lower reported toxicity in that group.

To evaluate QOL, the investigators used the Prostate Cancer Symptoms Indices (PCSI) for the proton beam and 3D-CRT patients and the Expanded Prostate Cancer Index Composite (EPIC) for the IMRT group.

Baseline mean QOL scores were compared to scores at the first follow-up (two to three months after treatment) and again at 24 months post-treatment. The researchers considered QOL scores exceeding half the standard deviation of the baseline mean score to be clinically meaningful differences.

“Our study provides a unique addition to existing research in this field and suggests that patients  treated with different radiation modalities may experience distinct patterns of side effects” Dr. Gray said. “Given the inherent limitations of any retrospective study, a prospective, randomized, controlled trial to investigate these differences will provide the most rigorous and valid comparison of these advanced technologies.” The Massachusetts General Hospital in Boston and the University of Pennsylvania in Philadelphia have partnered to launch just such a trial.

The findings are important because they reflect what patients are reporting. Previous studies of the three radiotherapy modalities have been based on clinician assessments of QOL. “Data from these studies showed that patients who undergo proton therapy may have worse adverse effects compared with IMRT, though there are limitations with these studies as there are with ours,” said Dr. Gray, who added that all radiotherapies are associated with a certain amount of toxicity.