Since the advent of radiation therapy for rectal cancer, there has been continual investigation of advancing technologies and techniques that allow for improved dose conformality to target structures while limiting irradiation of surrounding normal tissue. For locally advanced disease, intensity modulated and proton beam radiation therapy both provide more highly conformal treatment volumes that reduce dose to organs at risk, though the clinical benefit in terms of toxicity reduction is unclear. For early stage disease, endorectal contact therapy and high-dose rate brachytherapy may be a definitive treatment option for patients who are poor operative candidates or those with low-lying tumors that desire sphincter-preservation. Finally, there has been growing evidence that supports stereotactic body radiotherapy as a safe and effective salvage treatment for the minority of patients that locally recur following trimodality therapy for locally advanced disease. This review addresses these topics that remain areas of active clinical investigation. (C) 2016 Elsevier Inc. All rights reserved.
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