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

Abstract

9025 Background: There are no population-based studies of retroperitoneal sarcoma (RPS), and the use and timing of adjuvant radiotherapy (RT) in its treatment is controversial. The goal of our study was to examine the incidence and treatment of RPS, specifically regarding the use of adjuvant RT. Methods: We used the Surveillance, Epidemiology, and End Results (SEER) database to evaluate the incidence of RPS over a 29-year period (1973–2001). We evaluated the rate of surgery as well as the rate and timing of adjuvant RT. We then assessed the influence on treatment of factors including patient age, sex, race, marital status, year of diagnosis, and geographic location. 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=0.92). Most patients (1654; 70.4%) underwent surgical resection. RT was used in 428 patients (25.9%) who underwent surgery; RT was given postoperatively in 366 (85.5%), preoperatively in 20 (4.7%), and intraoperatively or unknown in 42 (9.8%). Patients who received adjuvant RT were on average 5 years younger than those who underwent surgery alone (p<0.0001). RT was more commonly used among whites than African Americans (25.8% vs. 16.7%; p=0.02) and there was significant variation in the use of adjuvant RT by geographic location (p=0.003). No associations were identified between the use of adjuvant RT and sex, marital status, or year of diagnosis. On multivariate analysis using logistic regression, race (p=0.01), age (p<0.0001), and geographic location (p=0.02) were independently associated with the use of adjuvant RT. Conclusions: The incidence of RPS, a rare disease, appears stable. Most patients who undergo surgery do not receive any adjuvant RT, and very few receive preoperative RT. Differences in adjuvant RT use found on the basis of demographic and geographic factors suggest that at least some treatment variations reflect individual and institutional practice patterns. These data, representing current practice, are important in considering how to implement future results of an ongoing randomized trial (ACOSOG 9031) comparing preoperative RT and surgery to surgery alone. No significant financial relationships to disclose.