Marieke van Son

130 CHAPTER 7 Table 2 – New-onset acute and late toxicity Domain Acute, number (%) Missing, number Late, number (%) Missing, number Genitourinary toxicity No toxicity Grade 1 Grade 2 Grade 3 48 (33.4%) 66 (45.8%) 30 (20.8%) 0 (0%) 6 46 (36.2%) 24 (18.9%) 52 (40.9%) 5 (3.9%) 23 Gastrointestinal toxicity No toxicity Grade 1 Grade 2 Grade 3 112 (77.8%) 29 (20.1%) 3 (2.1%) 0 (0%) 6 89 (70.1%) 32 (25.2%) 6 (4.7%) 0 (0%) 23 Erectile dysfunction No toxicity Grade 1 Grade 2 Grade 3 108 (75%) 4 (2.8%) 21 (14.6%) 11 (7.6%) 6 69 (54.8%) 6 (4.8%) 32 (25.4%) 19 (15%) 24 Legend: New-onset toxicity after ultrafocal salvage HDR-BT as graded by the Common Terminology Criteria for Adverse Events (CTCAE) 4.0. Any score above baseline in the acute (≤3 months) or late (>3 months) phase was considered new-onset toxicity. For the domains GU toxicity and ED, an explorative risk factor assessment was per- formed (Table 3). In both domains, baseline toxicity appeared to be the strongest pre- dictor of grade ≥2 toxicity (GU OR 14.8; ED OR 73.7). Within the GU domain, higher base- line IPSS (OR 1.11) and higher dose to the urethra (D10%) (OR 1.28) were also significant risk factors. Post-hoc cut-off analyses showed that the lowest contributive values to the model were IPSS ≥14 and urethra D10% ≥17 Gy. A baseline toxicity score of grade 2 or higher was a significant predictor for both GU toxicity and ED. To clarify the size of the relative risk of developing grade ≥2 GU toxicity or ED, figure 2 shows predicted probabilities at various levels of these risk factors.