Radiation therapy in non-surgically-treated nonmetastatic prostate cancer:Geographic and demographic variation

Objectives. To examine the geographic variation in the use of radiation to treat nonmetastatic prostate cancer and to identify factors that explain th e variation in the United States. Methods. This study was based on data from the nine geographic regions of t he Surveillance, Epidemiology, and End Results Program for 1983 through 199 6. Patients with localized or regional prostate cancer who did not undergo surgical treatment were included in the analysis. Logistic regression analy sis was used to investigate the influence of geographic and demographic fac tors on the use of radiation. The squared multiple correlation coefficient R-2 was used to measure the proportion of variation in the selection of rad iation explained by each factor of interest. Results. Compared with San Francisco, the adjusted odds ratios for 6 of the 8 geographic areas had highly significant P values, suggesting the use of radiation therapy varies from region to region. However, geographic locatio n only explained less than 3% of the total variation in the use of radiatio n. The geographic location explained a much higher proportion of variation in the youngest (younger than 55 years) and the oldest (80 years old or old er) groups. Overall, age was the most important factor that influenced the use of radiation. Conclusions. The finding that geographic location explains a significant pr oportion of the variation in the use of radiation in the youngest and oldes t age groups demonstrates the outcome of longstanding controversies in the nonsurgical treatment of prostate cancer. Documenting the impact of the int eraction of age and geographic location on the treatment approaches provide s for better understanding of the impact of patients and physicians making clinical decisions in the management of nonmetastatic prostate cancer. UROL OGY 57: 510-517, 2001. (C) 2001, Elsevier Science Inc.