Underlying anatomy for CTV contouring and lymphatic drainage in rectal cancer radiation therapy

Despite the low local recurrence rate that can be achieved by adequate surgery (total mesorectal excision--TME), radiation therapy was shown to play a significant role in reducing this risk. The widespread use of TME in many European Centers has introduced a new terminology and the need to identify the area at major risk for local failure using this surgical procedure. In the surgical series where extended extra-mesorectal surgery was performed, the role of lymphatic spread was evidenced, especially for low rectal cancer, through the pelvic parietal fascia and lateral pelvic spaces. The aim of this study was to better define some anatomic concepts and the main risk factors which impact on CTV contouring and field conformation in rectal cancer treatment. This information helps formulating guidelines for CTV contouring in daily radiotherapy practice, in order to define the best therapy, according to the tumor stage and location.