LAUSR

39 Background: Hydrogel spacers are a tool to improve dosimetry and overall quality of life with limited follow-up in men receiving radiotherapy for prostate cancer. This present study is a pooled analysis of a prospective cohorts with long-term follow-up quality of life (QOL) data with or without hydrogel spacers to minimize dose adjacent organs at risk. Methods: QOL was examined using the Expanded Prostate Cancer Index Composite (EPIC) to compare mean changes from baseline. A total of 215 patients from a randomized multi-institutional trial of radiation with or without hydrogel spacer with a QOL end-point were pooled with 165 non-randomized patients from a single institution with prospective QOL collection in both patients with or without hydrogel spacer. The proportions of men with minimally important differences (MIDs) relative to pre-treatment baseline in each domain were tested using repeated measures logistic models with pre-specified thresholds for clinically significant decline. Results: A total of 380 men were evaluated (64% with spacer and 36% without) with QOL data being available for 199 men beyond 24 months of follow-up (median: 39.5 months, range: 31-71.4 mo). Treatment with spacer was associated with less decline in average long-term bowel QOL (89.4 for control and 94.7 for experimental) with differences at > 2 years meeting the threshold of MID difference between cohorts (Bowel Score Difference from baseline: control = -5.1 spacer = 0.3 Diff = -5.4 p = 0.0003). When evaluated over time men without spacer were more likely to have 1xMID (5 points) declines in bowel QOL (p = 0.01). At long-term follow-up 1xMID was 36% without spacer vs 14% with spacer (p = 0.0006 OR = 3.5) while 2x MID was seen in 19% vs 6% (p = 0.008 OR = 3.6). The use of spacer was associated with improved bowel frequency (p = 0.002), reduced bleeding (p = 0.005) and less overall bowel problems (p = 0.007). Conclusions: In this pooled analysis of QOL after prostate radiotherapy with up to 5-years of follow-up utilization of a hydrogel spacer was associated with preservation of bowel QOL. This QOL benefit was preserved with long-term follow-up.