Marieke van Son

48 CHAPTER 3 Table 1 Continued Median / n IQR / % Unknown (%) Treatment characteristics Number of catheters 14 12-15 0 (0%) GTV(cc) 3.3 2.1-4.9 0 (0%) CTV(cc) 20.8 12.6-25.0 0 (0%) D90 CTV (Gy) 20.8 19.4-22.6 0 (0%) D95 CTV (Gy) 19.1 17.9-20.5 0 (0%) D10 urethra (Gy) 17.0 13.1-18.6 0 (0%) D1cc rectum (Gy) 11.5 8.2-12.3 0 (0%) D1cc bladder (Gy) 6.5 5.0-10.1 0 (0%) Abbreviations: HDR=high-dose-rate; IQR=interquartile range; TRUS=transrectal ultrasound; MRI=magnetic resonance imaging; AJCC=American Joint Committee on Cancer; iPSA=initial prostate specific antigen; PSADT=PSA doubling time. Treatment characteristics and dosimetry A median of 14 brachytherapy catheters were implanted. The GTV had a median volume of 3.3cc (2.1-4.9), which corresponded to a median CTV volume of 20.8cc (12.6-25). The median CTV D95% was 19.1Gy (17.9-20.5): in 14 patients, D95% was below 19Gy. Median CTV D90% was 20.8Gy (19.4-22.6), with 2 patients having a D90% below 17Gy. Reasons for suboptimal implant dosimetry were mainly transgression of organs at risk constraints, due to tumour position or size of the tumour volume. The urethral constraint was met in all patients. The rectal constraint was slightly exceeded in 10 patients (up to a maximum of 12.8Gy) and the bladder constraint in 2 patients (up to a maximum of 12.4Gy). Toxicity GU, GI toxicity and ED scores are depicted in figure 1 and table 2. In our previous report, we described one grade 3 GU toxicity: acute prostate haemorrhage resulting in gross haematuria and hospital admittance due to improper post-operative removal of an unfolded catheter. However, since this was not a direct side-effect of the radiation treatment itself, we consider this a perioperative complication in the current report. New grade 2 GU toxicity developed in 4 patients, including urinary frequency (n=3) and cystitis (n=1), all successfully treated with temporary medication. No grade 2 or higher GI toxicity occurred. New grade 2 ED after treatment was observed in 6 patients, new grade 3 ED occurred in 12 patients.