Radiation Therapy for Rectal Cancer: Current Status and Future Directions

Background: Treatment for rectal cancer has evolved over the past 70 years from surgery alone to the selective use of trimodality therapy for high-risk patients. Radiotherapy (RT) has improved the potential for tumor downstaging, thus enhancing sphincter preservation and local control. Methods: This article reviews the evolution of strategies that incorporate pelvic RT, intraoperative RT, and high-dose-rate endorectal brachytherapy (HDRBT). By tracing the arc of the pendulum that has swung from postoperative RT to preoperative RT, we address the current standard of care and explore the potential of novel radiation techniques and radiosensitizing agents to improve outcomes. Results: With randomized trial data confirming that preoperative RT in addition to chemotherapy improves local control and decreases acute and late morbidity, neoadjuvant programs have now demonstrated the prognostic significance of downstaging as well. Patients with tumors that have a good response to preoperative treatment have superior survival. Conclusions: Future studies will determine the optimal regimen to enhance the pathologic complete or near complete response rates for locally advanced disease. Advances in radiation technology are being investigated to determine whether efficacy can be increased and toxicity decreased so that more aggressive chemotherapeutic agents can be combined. With the growing improvements in combined modality therapy, a future of better rectal cancer outcomes looms brighter than ever before.