Improving chemoradiotherapy in rectal cancer

Abstract

The optimal management of rectal cancer remains a major challenge for oncologists. The treatment of stage II/III rectal cancer has historically been associated with a high risk of local recurrence and poor survival, which led to the development of adjuvant treatments in the hope of improving outcomes. The approach to adjuvant therapy for rectal cancer currently varies widely between Europe and the U.S. Postoperative adjuvant chemoradiation is the standard of care in the U.S. In contrast, in Europe, because there is a greater emphasis placed on preoperative imaging, meticulous surgical technique, and accurate pathologic reporting of the circumferential or radial margin, preoperative treatment (radiotherapy and chemoradiation) is used widely. The aims of preoperative radiotherapy and chemoradiation are to facilitate a curative resection (R0) and to increase the chance of performing sphincter-sparing procedures, and, therefore, to improve both survival and quality of life. This article reviews the clinical trials that led to these diverging standards of care. An interesting new approach in chemoradiation is the use of the oral fluoropyrimidine capecitabine as a combination partner for radiotherapy. Preclinical studies have demonstrated that the combination of capecitabine and radiotherapy has highly enhanced antitumor activity. This is most likely attributable to the upregulation of thymidine phosphorylase (the rate-limiting enzyme needed to convert capecitabine to 5-fluorouracil [5-FU]) in tumor cells following radiotherapy. A phase I study has consequently been performed to establish a feasible chemoradiotherapy combination. Capecitabine has the potential to replace bolus or continuous infusion 5-FU as the standard treatment for rectal cancer and offers a potentially enhanced therapeutic ratio. Oral chemotherapy has the additional advantage of simplifying chemoradiation and providing a treatment that is more appealing to patients.