Recommendations for CTV definition:
The following areas are at the greatest risk for relapse after prostatectomy and should therefore be included (= prostate bed):
Centrally: the urethra-vesical anastomosis;
Cranially: the bladder neck;
Posteriorly: up to but not including the outer rectal wall, cranially including the most posterior part of the bladder neck;
Caudally: including the apex (15 mm cranially from the penile bulb)
Laterally: up to the neurovascular bundles (if removed up to the ilio-obturatic muscles);
Anteriorly: including the anastomosis and the urethral axis
The CTV will include the above mentioned high risk areas with the following proposed margins:
5 mm in all directions (except the rectal wall) to account for microscopical extension;
Supplementary 5 mm in the posterior and lateral directions in the presence of incompletely resected ECE, but excluding the rectal wall;
Supplementary 5 mm in the direction of microscopically involved tumour margins as reported by the pathologist (except the rectal wall).
In all cases, the original site of the base of the seminal vesicles should be included. In the case of involvement of the seminal vesicles, we propose to include their original position and/or the remnants (present in 20% of the cases), without a further margin and treated to a lower dose (unless the rare case of involved margins at that level).
· In figure 2, a contouring example for patients scheduled for postoperative radiotherapy based on ECE is shown. Only the prostate bed, including the apex and the base of the seminal vesicles is included and displayed.
· For patients with invasion of the seminal vesicles, figure 3 shows the inclusion of the prostate bed including the apex and the original location of the seminal vesicles.
Recommendations for PTV definition:
In general, the margin from CTV to PTV depends on the experience and procedures of each individual centre. This can be reduced by daily on line image guided treatment execution but even then a minimum of 5 mm seems to be appropriate to account for organ motion.