Comparing Patient-Reported Outcomes in Patients With and Without Late Urinary Flare Following Stereotactic Body Radiation Therapy (SBRT) for Localized Prostate Cancer

Abstract

Stereotactic body radiation therapy (SBRT) is a newer treatment option for clinically localized prostate cancer. Late urinary symptom flare occurs transiently in a minority of patients 6 to 18 months following completion of treatment. Here, we compare patient-reported outcomes among patients with and without late urinary symptom flare following SBRT. At an academic medical center, 216 patients were treated for localized prostate cancer using the SBRT monotherapy protocol from June 2008-May 2010. Treatment was delivered using robotic SBRT at doses of 35-36.25 Gy in 5 fractions. Late urinary symptom flare was defined as an American Urological Association (AUA) symptom score ≥ 15 with an increase of ≥ 5 points above baseline six months after the completion of SBRT. Patient-reported outcomes and alpha-antagonist usage were assessed pretreatment at each follow-up visit. Patient-reported urinary symptoms were measured using the Expanded Prostate Cancer Index Composite (EPIC) short form. Of the 216 patients treated, 29 met criteria for late urinary symptom flare. Among patients with flare, the median age was 66 years (range 48-77) compared to 70 (range 49-90) for those without flare (p = 0.007). Use of alpha-antagonists was more common in patients without flare during the first 6 months following treatment, but was more common in patients with flare at and beyond 9 months. Among all patients, AUA symptom scores spiked transiently at 1 month post-treatment; a second transient increase was observed only among flare patients at 12 months. The EPIC urinary incontinence, irritative/obstructive, and bother domain scores declined at 1 month for all patients. Among flare patients only, a second transient nadir in these domains was observed at 12 months before returning to baseline at 24 months. Differences in patient-reported quality-of-life outcomes are observed between patients with and without late urinary symptom flare following SBRT. Specifically, declines in quality of life domains appear to parallel increases in urinary symptom scores among patients with flare. Notably, early toxicity does not appear to predict late toxicity in our cohort. Younger age appears to be a predictive factor associated with flare. Further studies are needed to determine which treatment variables confer greater risk of late urinary symptom flare.