Long-term quality of life outcome after proton beam monotherapy for localized prostate cancer

High-dose external radiation for localized prostate cancer results in favorable clinical outcomes and low toxicity rates. Here, we report long-term quality of life (QOL) outcome for men treated with conformal protons.

QOL questionnaires were sent at specified intervals to 95 men who received proton radiation. Of these, 87 men reported 3- and/or 12-month outcomes, whereas 73 also reported long-term outcomes (minimum 2 years). Symptom scores were calculated at baseline, 3 months, 12 months, and long-term follow-up. Generalized estimating equation models were constructed to assess longitudinal outcomes while accounting for correlation among repeated measures in an individual patient. Men were stratified into functional groups from their baseline questionnaires (normal, intermediate, or poor function) for each symptom domain. Long-term QOL changes were assessed overall and within functional groups using the Wilcoxon signed-rank test.

Statistically significant changes in all four symptom scores were observed in the longitudinal analysis. For the 73 men reporting long-term outcomes, there were significant change scores for incontinence (ID), bowel (BD) and sexual dysfunction (SD), but not obstructive/irritative voiding dysfunction (OID). When stratified by baseline functional category, only men with normal function had increased scores for ID and BD. For SD, there were significant changes in men with both normal and intermediate function, but not poor function.

Patient reported outcomes are sensitive indicators of treatment-related morbidity. These results quantitate the long-term consequences of proton monotherapy for prostate cancer. Analysis by baseline functional category provides an individualized prediction of long-term QOL scores. High dose proton radiation was associated with small increases in bowel dysfunction and incontinence, with more pronounced changes in sexual dysfunction.