BOSTON – Men who receive proton beam radiotherapy for prostate cancer have modestly better bowel function in the short term than do those who receive conformal or intensity-modulated radiation, but the effect is transient, investigators found.
At 2-3 months follow-up, patients treated with proton beam therapy (PBT) reported minimal decrements in bowel function, compared with patients treated with either 3D conformal radiotherapy (3D-CRT) or intensity-modulated radiotherapy (IMRT), who reported modest yet clinically meaningful decrements in bowel function, lead author Dr. Phillip J. Gray reported at the annual meeting of the American Society for Radiation Oncology.
Neil Osterweil/IMNG Medical Media
Dr. Phillip J. Gray
All three patient groups also had significantly lower urinary quality-of-life (QoL) scores at early follow-up compared with baseline, but these changes were considered clinically meaningful only for IMRT, said Dr. Gray, a resident in the Harvard Radiation Oncology program in Boston.
"Though significant, these differences appear transient, with all three groups showing clinically meaningful decrements in bowel quality of life at 2 years following the start of treatment, and minimally lingering urinary symptoms," he said.
The retrospective study looked at three cohorts of men treated with the different modalities: 153 treated with IMRT monotherapy in the PROST-QA consortium, 94 patients treated with PBT at Massachusetts General Hospital (MGH), and 123 treated with 3D-CRT at MGH and other Harvard-affiliated hospitals.
Patients treated with IMRT and PBT were evaluated with the Expanded Prostate Cancer Index Composite (EPIC) instrument; patients treated with 3D-CRT were assessed using the Prostate Cancer Symptoms Index (PCSI); PCSI scores were inverted to match those of the EPIC scale.
Treatment dose ranges were 75.6-79.2 Gy for IMRT, 74-82 Gy relative biological effectiveness values for PBT, and 66.4-79.2 Gy for 3D-CRT.
Mean patient-reported bowel QoL scores in the immediate post-treatment period were 93.3 on a scale of 0-100 for PBT, 78.5 for IMRT, and 88.2 for 3D-CRT (P vs. PBT less than .001 for both comparisons). The differences from baseline in IMRT and 3D-CRT, but not in PBT, were considered clinically significant.
At 24 months, mean respective bowel QoL scores were 91.8, 87.6, and 90.2, respectively, with clinically significant differences between PBT and the other two modalities.