Rectal cancer radiotherapy

Abstract

Adjuvant therapy for rectal cancer has undergone significant modifications over the past 30 years, including the addition of radiation therapy, significant improvements in surgical technique, and the administration of systemic therapy. Historically, curative resection commonly required an abdominoperineal resection and permanent colostomy. Adjuvant radiation therapy not only improved local control and overall survival, but allowed the opportunity for sphincter-preserving resections in patients with adequate sphincter function and tumors located approximately 1-2 cm from the dentate line. Local recurrence, a primary mode of failure in rectal cancer, has been improved by the development of the total mesorectal excision, with en-bloc resection of the rectum and its lymphovascular mesentery, the mesorectum. Removing micrometastatic disease within the mesorectum has also enhanced sphincter preservation without compromising local control or survival. Locoregional recurrence has remained a significant issue for patients with locally advanced disease (node positive or high T stage). Multiple studies have shown that the addition of chemotherapy further improves outcomes versus surgery alone or combined surgery and radiation, due both to the radiosensitizing properties of certain systemic agents as well as to the direct cytotoxic effect of the chemotherapy on micrometastatic disease. Adjuvant concurrent chemoirradiation in locally advanced rectal cancer confers a significant improvement in local control and overall survival compared with either modality alone. The future direction of treatment for rectal cancer will certainly consist of improved imaging and other diagnostic techniques to determine more accurately the need for adjuvant therapy. Multimodality therapy with radiotherapy administered in combination with systemic and biologic agents as radiation sensitizers is currently under investigation and may allow for improved local control and perhaps allow for minimizing the extent of surgery in selected situations.