Radiotherapy Planning and Contouring Protocol

For radiotherapy planning, CT was performed at slice thicknesses of 3 or 5 mm using a CT scanner (Hi-Speed Dxi; GE Healthcare, Buckinghamshire, UK) (Aquilion LB; TOSHIBA Medical Systems, Tochigi, JP). The clinical target volume (CTV) was contoured on the individual axial CT slices from each patient. The overall CTV included both the primary CTV and nodal CTV, including the pelvic and para-aortic lymph nodes. The pelvic lymph nodes were delineated on the planning CT in accordance with the Japan Clinical Oncology Group Gynecologic Cancer Study Group (JCOG-GCSG) consensus guidelines for the delineation of CTV for pelvic lymph nodes [13 (link)]. The CTV in the para-aortic region was contoured as the region between the psoas muscles, superiorly above the level of the renal artery (to the level of median T12/L1), and anteriorly encompassed the aorta and inferior vena cava with at least a 0.7-cm margin. The CTV was isotropically expanded by 7 mm to create the planning target volume (PTV). In addition, organs at risk (OARs), including the small bowel (contoured as a peritoneal space), rectum, bladder (both contoured as a whole organ), both kidneys, and spinal cord were delineated according to normal tissue contouring guidelines [14 (link),15 (link)]. No margin was added to the contoured OAR.