PO-0828: Analysis of the urethro-vesical region for urinary toxicity prediction after prostate radiotherapy

ESTRO 37 S432 patients treated with ADV or SALV intent at baseline (7.4 vs 4.6, p<0.0001, t-test) but not at 12 (7.8vs 7, p=0.26) or at 24 months (9 vs 7.3, p=0.07).The corresponding median values were 7 vs 4, 7 vs 6 and 8 vs 5.5, respectively.15%, 19% and 25% of pts experienced SUI at baseline and at 1 and 2 years, respectively.At MVA, the 3 variables independently predictive of SUI at 1 year were baseline ICIQ-SF score (OR 1.39), hypertension (OR 1.66) and TTRT (OR 0.97), (AUC 0.865, optimism1%), while baseline ICIQ-SF score (OR 1.35), ADT (OR 1.54 -2.24 when considering antiandrogens only) and EQD2 to PB (OR 1.15) emerged as the 3 variables independently predictive of SUI at 2 years (AUC 0.864, optimism 3%, Fig. 1). ConclusionOverall, UI in the first two years following ADV or SALV RT was mild, although a trend toward an increase of the fraction of pts experiencing SUI over time was observed.Slightly higher ICIQ-SF scores at 2 years were observed in the ADV subset.Baseline UI, higher EDQ2 RT doses, TTRT and ADT emerged as the strongest predictors of longterm SUI.