BMC Cancer 2009, 9:205 http://www.biomedcentral.com/1471-2407/9/205 Background Liposarcoma is the most common histology of soft tissue sarcoma and accounts for 20% to 30% of all sarcoma in adults [1-3]. Despite the skeletal and soft tissue are the most abundant tissue in the human body, soft tissue sar- coma consists of only 1% of neoplasms. Due to this low incidence of the soft tissue sarcoma, only a few studies reported some prognostic factors for liposarcoma, and optimal treatment strategies and thereby prognoses have not been fully defined yet [4-8]. Clinical behavior and prognostic features of soft tissue sarcoma are known to be associated with histology, and anatomic distribution. Conventionally, low grade lesions have higher incidence of local recurrence, and high grade tumors present with higher incidence of local recurrence and distant metastasis. Although surgical resection also remains as the primary treatment of all soft tissue sarcoma [7,9], radiotherapy has been extensively used in the treat- ment of sarcomas to improve cure rate and patients' qual- ity of life [10]. However, there are no confirmatory studies which directly compared preoperative with postoperative radiotherapy. Among them, ongoing Toronto study group's trial demonstrated preoperative radiotherapy had slightly better outcome in terms of morbidity and survival benefit even the study was underpowered [11]. There is still much controversy about the indications and appro- priate dose/timing for perioperative radiotherapy. Patients with high risk features for recurrence should be offered of pre- or postoperative treatment to further improve treatment outcome. In this study, we analyzed clinicopathologic features and prognostic factors for the histologically confirmed liposa- rcoma patients. We further attempted to devise a prognos- tic model specific for the disease in order to facilitate decision making in liposarcoma. Methods Patients Between January 1995 and May 2008, a total of 105 patients were diagnosed as liposarcoma by histologic exams at Samsung Medical Center. This retrospective study was reviewed and approved by the Samsung Medi- cal Center institutional review board (Seoul, Korea). Among them, 94 patients were treated by surgical resec- tion with curative intent. The other 11 patients were not available for further analyses along with complete clinical data due to patients' refusal for surgical resections or refer- rals after the relapses. Descriptive characteristics for all the 94 patients are listed in Table 1. Liposarcoma was classi- fied into 5 histologic subgroups based on Evans Classifi- cation [12]; well-differentiated, myxoid, dedifferentiated, round, and pleomorphic. No patient had distant metasta- sis at the time of surgical resection. Primary sites were categorized into lower extremity, upper extremity, trunk, retroperitoneum with or without contig- uous organ resection. A primary site was considered as upper extremity when it was at or beyond the shoulder joint, and as lower extremity when it was located in the groin, thigh, or leg. Retroperitoneal tumors were catego- rized as with or without contiguous organ resection (whether any of the following resections were performed: colon, small bowel, pancreas, spleen, bladder, uterus) according to the surgical record. Tumor burden was deter- mined by the maximum diameter of the primary tumor at the time of surgical resection. The type of surgery was reviewed from the surgeons' assessment as documented on the operative report. We analyzed specimen margins by gross and microscopic examinations in terms of six dimensions (superior, inferior, medial, lateral, anterior, and posterior). We defined a clear margin when there was no tumor at least 1 mm or more from the edge of the inked specimen. In addition, microscopically positive margin was defined when there was a tumor within ≤ 1 mm of the edge. Specimen margins were categorized as clear, microscopically positive, or grossly positive. None of the patient had received adjuvant chemotherapy. Thirty-one (33.0%) patients underwent postoperative external beam radiation therapy. Follow-up data included recurrence (local or distant metastasis), and vital status (alive without disease, alive with diseases, dead of other cause, dead as a result of sarcoma or sarcoma treatment). Statistics The primary end point was overall survival (OS), which was calculated using Kaplan-Meier method. OS was defined from the date of surgery to date of death related to the dis- ease or complication. Survival rates were compared for sta- tistical differences using log-rank test. OS was assessed with respect to following factors: age (both as a continuous var- iable and divided at the median), sex, histologic subtype, presentation status, primary site, tumor burden (both as a continous variable and divided into two groups), and resec- tion margin (negative, microscopically positive, grossly positive). We also analyzed 5- and 10-year OS. Multivariate analysis was performed using stepwise Cox proportional hazards regression modeling. P values less than 0.05 were considered statistically significant and all P values corre- sponded to two-sided significance tests. The disease free survival was defined as time from date of surgery to date of first recurrence for patients with negative or microscopi- cally positive resection margin. Results Patient characteristics Ninety-four liposarcoma patients who underwent surgical resection with curative intent were included in the analy- sis (Tab 1). There were 41 females and 53 males with median age of 56 years. The median tumor burden was 14 Page 2 of 8 (page number not for citation purposes)