Treatment
toxicity, small bowel, T4 disease
All of the patients underwent a CT simulation with a 5 mm slice thickness. The simulation was performed using a belly board apparatus and a full bladder protocol to reduce the toxicity to the small bowel and bladder. PET-CT images taken in the treatment position along with the CT simulation were combined for treatment planning.The gross target volume (GTV) was determined according to the PET-CT fusion images. The clinical target volume (CTV) included the pelvic lymphatic area (at the L5/S1 interspace), all the mesorectum, and the GTV. For T3 disease, the pelvic lymphatic area was defined to comprise the obturator, internal iliac, and presacral lymph nodes. The external iliac lymph nodes were also included in cases of T4 disease. The planning target volume (PTV) was delineated as a 1 cm margin in all directions beyond the CTV. The prescribed dose was 33 Gy/10 fr for the IC-CRT group. The biologically effective dose (BED3 and BED10) values were similar to a standard SC radiation dose (25 Gy/5 fr) (