Temporal and Regional Variations in the Use of Preoperative Radiation Therapy for Rectal Cancer

Objective: Preoperative (preop) chemoradiation therapy improves local control and reduces toxicity for stage II/III rectal cancer better than postoperative (postop) chemoradiation therapy. We examined the temporal and regional variations in the use of preop radiotherapy (RT) across the United States. Methods: Patients with stage II/III rectal cancer diagnosed between 1998 and 2005 who had a primary site resection were identified from the SEER database. The rate of preop RT use over time was plotted. Regression models were used to analyze regional variations. Results: From 1998 to 2005, an increase of 1.7 in the ratio of preop RT/postoperative RT was noted, whereas the ratio of RT/no RT increased only by 0.7. The ratio of preop RT/postop RT increased from 0.5 to 1 in 5 years (1998-2003) but from 1 to 1.5 in 2 years (2003-2005). Multivariate regression analysis showed: patients with stage II disease were more likely than those with stage III disease, younger patients were more likely than older patients, and males were more likely than females to receive preop RT. Whites were more likely to receive preop RT than nonwhites for stage III disease only. Patients treated in the San Francisco region, Hawaii, New Mexico, Seattle, and Los Angeles were more likely to receive preop RT than were patients in the Connecticut, Detroit, Iowa, Utah, Atlanta, and San Jose/Monterey regions. Conclusions: The increasing use of preop RT varies across US regions and patient subgroups. Further studies should evaluate potentially modifiable factors contributing to these variations.