Radical treatment of extraskeletal myxoid chondrosarcoma: A retrospective analysis of long-term outcomes and inflammatory prognostic factors.

e23561 Background: Extraskeletal myxoid chondrosarcoma (EMC) is an ultra-rare soft tissue sarcoma characterised by recurrent NR4A3 gene rearrangements. Real-world data on survival and prognostic biomarkers is limited. Therefore, we evaluated long-term oncological outcomes and inflammatory prognostic factors in a cohort of patients (pts) treated with curative intent at a national reference centre. Methods: We retrospectively analysed institutional records to identify consecutive pts with histologically confirmed EMC who underwent a curative-intent surgery over the last 25 years. Kaplan–Meier analysis was used to calculate the survival outcomes including overall survival (OS), relapse-free survival (RFS) and distant metastasis-free survival (DMFS). Log-rank test was used to determine the prognostic impact of pre-treatment peripheral blood biomarkers (neutrophil-to-lymphocyte ratio [NLR], platelet-to-lymphocyte ratio [PLR], lymphocyte-to-monocyte ratio [LMR], systemic immune-inflammation index [SII]). Results: 37 pts were included (median age 57.6 years; range 24.9–80.3; 51.4% female). Low-grade tumours accounted for 67.6%, while 24.3% were high-grade. Surgical resection margins were R0 in 24 (64.9%) pts, and R1/R2 in 11 (29.7%) pts. Metastasis were present at diagnosis in 5 (13.5%). Pre-operative radiotherapy was used in 24 cases, mostly 5 x 5 Gy. For the entire cohort median OS, RFS, and DMFS were 162.76, 46.88, and 58.87 months, respectively. Low values (below median) of PLR, LMR, MLR and SII were reported in pts with prolonged OS (216–276 months), whereas high values were associated with shorter survival curves. Also, high (above median or median) NLR tended to be associated with shorter OS than low NLR. However, statistical significance was not reached. Conclusions: In EMC pts treated with radical intent, long-term survival is favourable, although characterised by substantial recurrence and metastatic risk. Systemic inflammatory indices, derived from routine blood tests, identify prognostically distinct subgroups and may complement established clinicopathological factors. However, further research on a larger group is needed.