Variation in Clinical Target Volumes for Post-prostatectomy Patients and Effect on Normal Tissue Complication Probability

摘要

Background: Modern radiotherapy requires accurate contouring which may suffer in the post-surgical setting. We estimated post-prostatectomy inter- and intra-rater contouring reliability and assessed the effect on bladder and rectal normal tissue complication probability (NTCP). Methods: Four physicians each contoured two different treatment plans, separated by at least seven days, on 15 patients receiving post-prostatectomy four-field 3D-conformal?radiotherapy. The Pinnacle 8.0 system determined CTV volume, shape, and center-of-volume coordinates. Inter- and intra-rater reliability was estimated using Gilder’s method. NTCP were estimated using parameters TDsub50/sub=8190 cGy, n=0.23, m=0.19 for rectum and TDsub50/sub=8000 cGy, n=0.5, m=0.11 for bladder. Results: Reliability estimates for center-of-volume were ≥0.993. Inter-rater reliability was ≤0.290 and intra-rater reliability between 0.375-0.729 for shape and volume. Inter-rater reliability estimates of NTCP were 0.398 for bladder and 0.0936 for rectum with highest inter-rater variation 4% and 8%, respectively. Intra-rater reliability NTCP estimates were 0.650 for bladder and 0.186 for rectum, with highest intra-rater NTCP variation 3% and 7%, respectively. Conclusions: Center-of-volume coordinates showed excellent agreement while volume and shape showed poor inter-rater, but moderate intra-rater, agreement. NTCP estimates showed generally poor agreement, but these differences were clinically significant only for rectum (not bladder), based on an a priori definition.