Adjuvant radiation for rectal cancer: do we measure up to the standard of care? An epidemiologic analysis of trends over 25 years in the United States.

PURPOSE In the United States, adjuvant radiation therapy is currently recommended for most patients with rectal cancer. We conducted this population-based study to evaluate the rate of radiation therapy and the factors affecting its delivery. METHODS We used the Surveillance Epidemiology and End Results database to assess treatment of patients with nonmetastatic rectal cancer diagnosed over a 25-year period (1976 through 2000). We evaluated the rate of radiation therapy use and its timing (preoperative vs. postoperative) and the influence of factors such as tumor stage and grade; patient gender and race; and geographic location. RESULTS In this 25-year period, 45,627 patients met our selection criteria. The rate of radiation therapy use increased dramatically over time: from 17 percent of advanced-stage patients in 1976 to 65 percent in 2000 (P < 0.0001). Until 1996, the increase was due almost entirely to postoperative radiation therapy. Since 1996, the rate of preoperative radiation therapy use has increased (P < 0.0001) and the rate of postoperative radiation therapy use has begun to decline. We found, after controlling for the year of diagnosis, that female patients, African Americans, older patients, and patients with low-grade lesions were less likely to undergo radiation therapy (P < 0.0001). Geographic location was also an important predictor of radiation therapy use. CONCLUSIONS The use of radiation therapy for patients with rectal cancer has dramatically increased over the 25-year period studied, with a recent shift to the use of preoperative radiation therapy; however, in 2000, over 30 percent of patients with advanced-stage nonmetastatic rectal cancer did not undergo radiation therapy. Given the variation in radiation therapy use that we found to be due to demographic factors, access to adjuvant radiation therapy can be improved.