Stereotactic Body Radiation Therapy (SBRT) for Prostate Cancer in Men with a High International Prostate Symptom Score (IPSS > 15)

Abstract

Patients with a high pretreatment IPSS may have higher rates of late urinary morbidity after radiation therapy for prostate cancer. Stereotactic body radiation therapy (SBRT) delivers fewer high-dose fractions of radiation, which may be radiobiologically favorable to the conventional low-dose external beam fractions commonly used for prostate cancer radiotherapy. The urinary toxicity associated with SBRT, however, remains unclear in treated patients with a high IPSS. We report our early experience using SBRT for localized prostate cancer in patients with pretreatment IPSS > 15. Localized prostate cancer patients with pre-treatment IPSS > 15 and a minimum follow up of 3 years treated with SBRT from January 2009 to December 2012 were included in this retrospective review of prospectively collected data from our institutional database. These patients were treated to 35-36.25 Gy in 5 fractions. Urinary quality of life was assessed before and after treatment using the Expanded Prostate Cancer Index Composite (EPIC-26). The EPIC urinary domain is scored on a range from 0 to 100 with higher values representing more favorable urinary symptoms. Late urinary symptom flare was defined as having an IPSS score increase of ≥ 5 points above baseline 6 months after the completion of SBRT. Toxicities were scored using the CTCAE v4. 48 patients (18 low, 20 intermediate, and 10 high risk per the D’Amico criteria) at a median age of 71 years (range 53-90 years) received SBRT with a median follow up of 4.5 years. The median prostate size was 39.5 cm3 (range 13.5-108 cm3) and 31% patients received ADT. A mean baseline IPSS score of 19 significantly decreased to 16 at 1 month (p = 0.037) and 12 at 6 months (p < 0.001). A mean baseline EPIC-26 obstructive/irritative score of 71 significantly increased to 80 at 6 months (p < 0.001). There was no significant change from the mean baseline EPIC-26 urinary incontinence score at any point during follow up. The 3-year cumulative incidence rate of late urinary symptom flare was 19%. The 3-year rate of grade 2 GU toxicities was 35%; no grade 3 GU toxicities were observed. SBRT for clinically localized prostate cancer was well tolerated in men with baseline IPSS > 15. Surprisingly, urinary quality of life improved following treatment. Late urinary symptom flares were observed, but the majority resolved with conservative management. GU toxicity rates were comparable to men with normal baseline IPSS scores.