Adjuvant radiation therapy for colorectal cancer

Abstract

Despite apparently complete resection of cancers of the rectum or colon, many patients have recurrences in the area from which their primary cancer was excised and in more distant organs. Radiation therapy has been used either alone or in combination with chemotherapy as an adjuvant to surgery to reduce the risk of recurrence. The literature describing the results of adjuvant radiation treatment for colorectal cancer was reviewed. In randomized studies in patients with moderately advanced rectal cancers (T2-4 N0, M0 or N1-3, M0) adjuvant radiation therapy has often reduced the risk of pelvic recurrence, but has had little effect on survival rates or the risk of extrapelvic metastases. Recent reports show that combined radiation and chemotherapy can improve both disease-free survival and survival rates. Such treatment has caused only moderate toxicity in most studies. Nonrandomized studies in patients in whom small superficial rectal cancers are treated by local excision suggest that adjuvant radiation therapy reduces the risk of pelvic recurrence after this limited surgery and allows anorectal function to be preserved. Strategies similar to those developed for the treatment of rectal cancer are being studied in patients with colon cancer. In moderately advanced rectal cancers, the combination of chemotherapy and radiation is more effective than radiation alone in reducing local recurrence and increasing survival rates. Additional trials are needed to improve results and to refine drug and radiation schedules. Radiation alone may be sufficient as an adjuvant treatment when combined with local excision of small rectal cancers. The role of radiation in the adjuvant treatment of colon cancer is investigational. There is a need to more accurately delineate the patients with colorectal cancer most likely to benefit from adjuvant therapy.