Background: Liposarcoma (LPS) represents the most common soft-tissue sarcoma.The aim of this prospective and exhaustive population-based study is to explore the impact of medical practices conformed to CPG's on survival of patients with localized LPS in a region of 6 million inhabitants. Methods: Between 2005 and 2007, 133 patients out of 141 with an initial diagnosis of localized LPS and residing in the RA region (France), were enrolled. The prognostic impact of adherence to CPGs on progression-free survival (PFS) and overall survival (OS) was assessed with a multivariate Cox model analysis including all potential prognostic factors (PF). Results: The median age was 61 years (range 26-89). Sex ratio: M/F was 1.5; the histological subtypes were: well differentiated LPS (n=86, 64.5%), dedifferenciated LPS (n=29, 22%), myxoid (n=12, 9%) and pleiomorphic (n= 6, 4.5 %). Histological grade was low in 96 patients (73%), intermediate in 16 (17%) high in 12 (9%) and unknown in 2 (1%), 48.8% of tumors were localized in limbs (n=65), 44.3% in retroperitoneum (n=59) and 6.8% in other sites (n=9). The adherence to CPGs for patients with localized LPS was 53%, for initial surgery. In multivariate analysis, adherence of surgery to CPGs was the strongest independent prognostic factor (PF) of PFS (HR: 0·32; 95% CI [0·16-0·61]), along with age at diagnosis ≤60 years (HR: 0·42; 95% CI [0·21-0·83]), grade (low vs. high, HR: 0.16, 95% CI [0.07-0.37]; intermediate vs. high, HR: 0.8, 95% CI [0.34-1.85]) and tumor site (limbs vs. retroperitoneal tumors HR: 0·49, 95% CI [0·24-1·01]; head, neck and thoracic vs. retroperitoneal tumors HR: 0·12, 95% CI [0·02-0·93]). For OS, independent PF were adherence to CPGs for surgery (HR: 0.36 95% CI [0.15, 0.84]), age at diagnosis ≤60 years (HR: 0·34; 95% CI [0·14-0·85]) and grade (low vs. high, HR: 0.05, 95% CI [0.02-0.15]; intermediate vs. high, HR: 0.53, 95% CI [0.22-1.29]). Conclusions: In this exhaustive population-based study, adherence to CPGs is one of the major significant PF of survival for localized LPS patients. Organization of rare cancer care and physician's education are urgently needed.