The changing role of radiation in the post-TME ERA of rectal cancer

Total mesorectal excision (TME) for rectal cancer is now considered standard in the surgical treatment of rectal cancer. The application of this technique has resulted in a pooled pelvic recurrence rate of approximately 7%. Preoperative and postoperative radiation further decreases the local regional recurrence (LRR) rate in patients with rectal cancer but the reduction in risk is counterbalanced by increased short and long term toxicity. Lower LRR rates have not uniformly translated into more favorable overall survival. In addition, advances in imaging have resulted in more accurate pretreatment staging and have improved the ability to stratify patients based on risk of recurrence. Given low pelvic recurrence rates after TME-based surgery alone, the risks and toxicities of pelvic radiation, and superior imaging to select high risk patients, radiation may not be requisite in the treatment of all rectal cancer patients. In this review, we discuss the current status of radiation and LRR rates in rectal cancer after definitive surgical resection with respect to specific subsites and stages of disease, examine the impact of imaging in the selection of patients for radiation, and raise the possibility that predictive biomarkers may help to identify patients who may not require pelvic radiation.