Introduction. Chondrosarcoma (ChSa) is the second most common primary malignant bone tumour, after osteosarcoma. The aim of this study is to analyse the prognostic factors in patients operated on ChSa of the pelvic bone with limb sparing on the basis of a large retrospective group of patients. Aspects of the surgical technique are also presented, taking into account the location of the tumour within the pelvis. An attempt was also made to define the criteria for selecting patients for whom

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... al and limb-sparing surgery is possible. Material and methods. We analysed 53 consecutive patients with chondrosarcoma of the pelvic and sacral bones after surgery performed at the Department of Soft Tissue/Bone Sarcoma and Melanoma in Maria Sklodowska-Curie National Research Institute of Oncology in Warsaw, Poland, between 1998 and 2020. Patients had surgery with sparing of the lower limb with the intention of cure. Results. There were 34 patients with G1 grade, G2 -16, and G3 -3. The R0 resection margin was achieved in 36 cases, the R1 margin in 11, and the R2 margin in 5 cases. The 5-and 10-year overall survival rates for the entire group were 84% and 65%, respectively. The 5-year and 10-year disease-free survival (DFS) probabilities were 65% and 43%, respectively. Conclusions. Multivariate analysis of the studied group of patients showed that the resection margin was a statistically significant factor determining prognosis (patients after R0 surgery margin have about 5 times lower death risk compared to patients after non-radical surgery with R1 or R2 margin).