UNASSIGNED: 78 Background: While maximum @entity5 diameter (MTD), as identified on radical prostatectomy (RP) specimens, has been associated with @entity263 recurrence, the prognostic significance of this variable is unknown in the context of salvage external beam radiation therapy (EBRT) following a rising PSA after RP. Here, we investigate associations between MTD and outcomes in this setting. METHODS: From an IRB approved retrospective single-institutional cohort, 575 @entity1 treated with salvage radiation therapy (SRT) were identified, with MTD data available on 173. ANOVA and chi-square were utilized to compare prognostic variables with MTD. The impact of MTD on biochemical failure (BF), @entity3 ( @entity3 ), @entity263 -specific mortality (PCSM) and @entity1349 ( @entity1349 ) was assessed on univariate and multivariate analysis using Kaplan-Meier and Cox-proportional hazards regression. RESULTS: Median follow up was 76.5 months (IQR, 46.5-104.0) and median MTD was 18 mm (IQR, 13-22). Median RT dose was 68.4 Gy (IQR, 64.8-68.4). MTD size correlated with pT-stage, Gleason score, and presence of seminal vesicle invasion or lymph node invasion. Receiver operator characteristic (ROC) curve analysis was used to correlate MTD with clinical end-points and identified 14 mm as the most prognostic cut-point. A MTD >14 mm was associated with a 1.8, 4.0 and 8-fold increase in the risk of BF (p<0.02), @entity3 (p<0.002), and PCSM (p<0.02), respectively. As a continuous variable, on multivariate analysis, MTD was shown to be a marginally significant predictor of @entity1349 (p=0.056, HR [95%] 1.6 [1.0-2.5]), and a significant predictor of PCSM (p<0.03, HR [95%] 2.0 [1.1-3.8]) and @entity3 (p=0.01, HR [95%] 1.7 [1.1-2.6) but not BF. In this model, for every 10 mm increase in MTD, there is a 1.7, 2.0, and 1.6 fold risk of @entity3 , @entity263 death and overall death, respectively. CONCLUSIONS: As a categorical and continuous variable, MTD is a significant predictor of @entity263 outcomes following SRT and should be used in clinical decision making in this population and in future clinical risk assessment tools.

Maximum XXXX diameter as a predictor for outcome following salvage radiation for @entity263 .

@entity1 :: ('9606', 'Species') :: ['patients'] @entity263 :: ('MESH:D011471', 'Disease') :: ['prostate cancer'] @entity5 :: ('MESH:D009369', 'Disease') :: ['tumor'] @entity3 :: ('MESH:D009362', 'Disease') :: ['metastasis', 'Mets'] @entity1349 :: ('MESH:D011475', 'Disease') :: ['OS', 'overall survival']
@entity5 :: (MESH:D009369,Disease) :: ['tumor']
