BMC Cancer 2009, 9:205 http://www.biomedcentral.com/1471-2407/9/205 FOivgeurraell s3urvival of patients by prognostic model Overall survival of patients by prognostic model. Group 1 (n = 66), no adverse factors; Group 2, one or two adverse factors (n = 28). grossly positive margin, P < 0.001), primary site (retroper- itoneum or deep trunk, P = 0.009) and tumor burden (more than 10 cm, P = 0.013). The forward Cox regression model was used to establish independent prognostic fac- tors. Independent prognostic factors for survival were his- tologic variant (P = 0.001; HR, 5.1; 95% CI, 2.0 – 12.9), and margin status (P = 0.005; HR, 4.1; 95% CI, 1.6–10.5) as shown in Table 3. All the patients had complete infor- mation on the two parameters and included in the prog- nostication. The prognostic grouping was performed according to the following criteria: group 1 (n = 66), no adverse factors; group 2, one or two adverse factors (n = 28). The Kaplan-Meier survival curves according to the prognostic index are shown in Figure 3 (P < 0.001). The prognostic model separated patients into two risk groups with significantly different survival outcomes. The 5-year OS rate for group 1, and 2 were 91.9%, 45.5%, respec- tively. Table 3: Prognostic factors for survival in Multivariate Analysis Discussion Liposarcoma is the most common soft tissue sarcoma which accounts for about 20% of sarcoma in adults [14]. Histologic classification have been well established by the current World Health Organization, which is almost iden- tical to the paradigm implemented by Enzinger and Win- slow [15]. The 5 histologic subgroups of liposarcoma pursue different natural clinical course not only in terms of clinical features but also the survival outcome. Never- theless, current clinical practice is not optimized accord- ing to different histologic subtypes and clinical protocol often does not reflect such difference. In this study, we ret- rospectively analyzed a homogeneous cohort of primary liposarcoma patients. To improve the risk based stratifica- tion for treatment, we also attempted to establish a prog- nostic model for this subset of patients. In the present study, the most common subtype was well- differentiated liposarcoma which accounted for approxi- mately 50% of all cases. The overall survival was well strat- ified by histologic subtype, which was concordant with the results from previous studies [13,16]. Multivariate analyses further demonstrated that histologic subtype was an independent prognostic factor for survival. High grade tumors (dedifferentiated, round cell, pleomorphic tumors) were associated with approximately 5-fold increased risk of deaths compared with low grade tumors. The efficacy of radiation therapy to improve local control has been well reported in the previous randomized trials of extremity soft tissue sarcomas [17,18]. In contrast to extremity sarcoma, the role of adjuvant radiotherapy for patients with retroperitoneal sarcoma is not well clarified. Some studies revealed that adjuvant radiotherapy reduces the risk of local recurrence and improves local control [19,20]. Thereby some patient with negative resection margin had received adjuvant radiotherapy when primary tumors are large-sized or deep retroperitoneal origin. The addition of adjuvant radiotherapy seems to confer sur- vival benefit in low grade tumors although limited by ret- rospective nature of the analyses. As illustrated in Figure 2A, the impact of adjuvant radiotherapy on survival was Variables Univariate Multivariate Histologic variant (high vs Low) Margin status (positive vs negative) Primary site (trunk or retroperitoneum vs extremity) Tumor burden (> 10 cm vs ≤ 10 cm) P < 0.001 < 0.001 0.009 0.013 HR (95% CI) 5.1 (2.0–12.9) 4.1 (1.6–10.5) - - P 0.001 0.005 0.239 0.164 Survival (%) 5-year OS 48.6 vs 86.1 44.0 vs 83.0 61.1 vs 90.0 67.3 vs 100.0 Page 6 of 8 (page number not for citation purposes)