Accurate target definition is critical for the appropriate application of radiation therapy. In 2008, the YYYY (YYYY) published an international collaborative atlas to define the clinical target volume (CTV) for intensity modulated pelvic radiation therapy in the post-operative treatment of endometrial and cervical cancer. The current project is an updated consensus of CTV definitions, with removal of all references to bony landmarks and inclusion of the para-aortic and inferior obturator nodal regions.

An international consensus guideline working group discussed modifications of the current atlas and areas of controversy. A document was prepared to assist in contouring definitions. A sample case abdominal/pelvic CT was made available, on which experts contoured targets. Targets were analyzed for consistency of delineation using an expectation-maximization algorithm for simultaneous truth and performance level estimation (STAPLE) with kappa statistics as a measure of agreement between observers.

Sixteen participants provided thirteen sets of contours. Participants were asked to provide separate contours of the following areas: vaginal cuff, obturator, internal iliac, external iliac, pre-sacral, common iliac, and para-aortic regions. There was substantial agreement for the common iliac region (sensitivity 0.71, specificity 0.981, kappa 0.64), moderate agreement in the external iliac, para-aortic, internal iliac and vaginal cuff regions (sensitivity 0.66, 0.74, 0.62, 0.59 specificity 0.989, 0.966, 0.986, 0.976, kappa 0.60, 0.58, 0.52, 0.47 respectively), and fair agreement in the pre-sacral and obturator regions (sensitivity 0.55, 0.35 specificity 0.986, 0.988; kappa 0.36, 0.21 respectively). A 95% agreement contour was smoothed and a final contour atlas was produced based on consensus.

Agreement among the participants was most consistent in the common iliac region and least in the pre-sacral and obturator nodal regions. The consensus volumes formed the basis of the updated XXXX/YYYY Oncology post-operative atlas. Continued patterns of recurrence research are encouraged to refine these volumes.