Clinical to planning target volume margins in prostate cancer radiotherapy

The knowledge of inter- and intrafraction motion and deformations of the intrapelvic target volumes (prostate, seminal vesicles, prostatectomy bed and lymph nodes) as well as the main organs at risk (bladder and rectum) allow to define rational clinical to planning target volume margins, depending on the different radiotherapy techniques and their uncertainties. In case of image-guided radiotherapy, prostate margins and seminal vesicles margins can be between 5 and 10 mm. The margins around the prostatectomy bed vary from 10 to 15 mm and those around the lymph node clinical target volume between 7 and 10 mm. Stereotactic body radiotherapy allows lower margins, which are 3 to 5 mm around the prostate. Image-guided and stereotactic body radiotherapy with adequate margins allow finally moderate or extreme hypofractionation. (C) 2016 Societe francaise de radiotherapie oncologique (SFRO). Published by Elsevier Masson SAS. All rights reserved.