Retroperitoneal sarcoma: A population-based analysis of epidemiology, surgery, and radiotherapy

BACKGROUND. No population-based studies of retroperitoneal sarcoma (RPS) have been conducted, and the use and timing of adjuvant radiotherapy for RPS is controversial. The objective of this study was to examine the incidence and treatment of RPS, specifically regarding the use of adjuvant radiotherapy. METHODS. The Surveillance, Epidemiology, and End Results (SEER) database was used to evaluate the incidence of RPS over a 29-year period (1973-2001). The rate of surgery, the rate and timing of adjuvant radiotherapy, and the influence of demographic factors on treatment were evaluated. RESULTS. A total of 2348 cases of RPS were identified. The mean annual incidence of RPS was 2.7 cases per 10⁶ persons and did not change significantly over time (2.6 in 1973 vs. 2.8 in 2001; P = .92). Most patients (1654; 70.4%) underwent surgical resection. Radiotherapy was used in 428 patients (25.9%) who underwent surgery; radiation was given postoperatively in 366 (85.5%), preoperatively in 20 (4.7%), and intraoperatively or unknown in 42 (9.8%). Patients who received any adjuvant radiotherapy were on average 5 years younger than those who underwent surgery alone (P < .0001). Radiotherapy was more commonly used among whites than African Americans (25.8% vs. 16.7%; P = .02) and there was significant variation in the use of adjuvant radiotherapy by geographic location (P = .003). On multivariate analysis, race (P = 0.004), age (P < .0001), and geographic location (P = .006) were independently associated with the use of adjuvant radiotherapy. CONCLUSION. The incidence of RPS, a rare disease, appears stable. Most patients who undergo surgery do not receive any adjuvant radiotherapy, and very few receive preoperative radiotherapy. Differences in adjuvant radiotherapy use related to demographic and geographic factors suggest that at least some treatment variations reflect differences in individual and institutional practice patterns.