BMC Cancer 2009, 9:205 http://www.biomedcentral.com/1471-2407/9/205 more prominent in low grade sarcomas than high grade tumors. Interestingly, the local control rate was consider- ably lower in the high grade tumor group when compared with low grade group following postoperative radiother- apy (local failure rate 22.7% vs 55.6%, P = 0.08). In sup- port of this, there were no differences in margin status between the two groups. In addition, to clarify the benefit of radiotherapy, we also analyzed significant prognostic factors for DFS and efficacy of adjuvant radiotherapy for patients with negative and microscopically positive mar- gins. The DFS was significantly different according to the histologic subtype, and patients with low grade liposar- coma demonstrated better DFS with postoperative adju- vant radiotherapy. The underlying mechanisms that cause these changes are uncertain. It is possible that patients with high grade tumor had slightly more retroperitoneal site and positive resection margins than those with low grade. Even though this is the retrospective study with rel- atively small sample size, we emphasize that these results should be cautiously interpreted and prompt future pro- spective studies. To improve risk-based stratification for therapy, we attempted to establish a prognostic model specifically devised for patients treated by surgical resection with cur- ative intent. At multivariate analyses, histologic variant (P = 0.001; HR, 5.1; 95% CI, 2.0–12.9), resection margin sta- tus (P = 0.005; HR, 4.1; 95% CI, 1.6–10.5) retained statis- tical significance. The prognostic grouping was based on scoring system of the adverse factors and yielded distinc- tive sets of two groups with different survival outcome (5- year OS rates for group 1, and 2 were 91.9%, and 45.5%, respectively.) Given a poor prognosis of patients with one or two adverse factors in the model, this subgroup of patients may potentially benefit from more aggressive postoperative treatment. Hence, the role of adjuvant chemotherapy with or without radiotherapy may be stud- ied in this subgroup of patients. Our prognostic model demonstrated two groups of patients with distinct prog- nostic discrimination. More aggressive postoperative treatment such as combined modalities with chemother- apy and radiotherapy should be offered in the context of clinical trials in this particular subgroup of liposarcoma patients. Nonetheless, prospective study is needed to vali- date the model on larger population. In this study, the frequency of retroperitoneal primary site was high accounting for half of the cohort. Previous stud- ies in western population demonstrated relatively lower incidence of retroperitoneal primary site ranging from 25–33.4% of all cases [4,13]. Retroperitoneal tumors usu- ally presented with large-sized mass and involvement of multiple contiguous organs and thus, a wide excision with adequate resection margin may not have been technically feasible. Its anatomic characteristics may render relatively poor survival outcome of this study compare to previous studies which have shown 75% to 83% of 5-year overall survival. Conclusion Histologic subtype, and margin status are independently associated with disease specific survival, and patients with low grade histology had benefit from adjuvant radiother- apy. Proposed model for primary liposarcoma demon- strated distinct groups of patients with good prognostic discrimination. The impact of adjuvant radiotherapy on OS and DFS were more prominent in low grade sarcomas than high grade tumors. We hope our study may facilitate further prospective study and alternatively clinical deci- sion making in liposarcoma, combined with reliable molecular markers. Competing interests The authors declare that they have no competing interests. Authors' contributions HSK drafted the manuscript. HSK, SYY, HJJ, YLC, GHA, SWS, DHL, YCA, SK collected the data and performed the statistical analysis. SWS, DHL, YCA, SK, JL and JOP fol- lowed the patients. SK, JOP, and JL designed the study and helped with the manuscript. All authors read and approved the final manuscript. References 1. Jemal A, Siegel R, Ward E, Hao Y, Xu J, Murray T, Thun MJ: Cancer statistics, 2008. CA Cancer J Clin 2008, 58(2):71-96. 2. ECDM Fletcher KU, Mertens F: World Health Organisation: classificationo of tumors: pathology and genetics of tumours of soft tissue and bone. IARC Press; 2002:35-46. 3. Miettinen M: Diagnostic soft tissue pathology. Oxford, Churchill Livingstone; 2003:1450-1408. 4. Linehan DC, Lewis JJ, Leung D, Brennan MF: Influence of biologic factors and anatomic site in completely resected liposar- coma. J Clin Oncol 2000, 18(8):1637-1643. 5. 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