Abstract 88P
Background
Primary malignant (PM) bone sarcomas (BS) account for 0.2% of all cancers. More than 90% of BS are osteosarcomas (OTS), Ewing sarcomas (ES) or chondrosarcomas (CS). Other extremely rare BS can also occur, contributing to their heterogeneity. The rarity of PM BS limits current knowledge on these tumors. Therefore, we aimed to assess the characteristics, outcomes and predictive factors of patients with PM BS.
Methods
Retrospective study on adult patients with diagnosis of PM BS, between 2013 and 2021, at our institution. Progression-free survival (PFS) and overall survival (OS) were analyzed by Kaplan-Meier method and predictors of mortality by Cox regression.
Results
81 patients were enrolled. 57% (n=46) were men. 42% (n=34) of cases were CS, 26% (n=21) OTS and 17% (n=14) ES. Less frequently we observed giant bone cell tumors (GCT) in 10% (n=8) of patients, chordomas (CM) in 4% (n=3) and perivascular epithelioid cell tumors (PEComa) in 1% (n=1). The median age was 60 for CS, 31 for OTS, 28 for ES, 36 for GCT and 73 for CM. The most common affected site was the appendicular skeleton (femur), with the exception of CM. Initial metastatic disease was noted in 3% of CS, 5% of OTS and 43% of ES; lung was the main site of metastasis. Upfront surgery (SGR) was performed in 97% of CS, 43% of OTS, 38% of GCT, all cases of PEComa and CM. Perioperative chemotherapy (pChT) + SGR was performed in 57% of OTS and 57% of ES. 50% of GCT received perioperative denosumab + SGR. 43% of ES received palliative ChT, 12% of GCT denosumab and 3% of CS best supportive care. Median time of follow-up was 58 months. 2-year PFS was 63% and 2-year OS was 84%. BS subtype was associated with the OS: GCT and CS had improved OS compared to other subtypes (p=0.038 and p=0.046, respectively). Elevated lactate dehydrogenase (LDH) at diagnosis and mitotic count (> 19 mitoses/high power field [HPF], excluding GCT) were both predictors of mortality (HR=2.952, 95% CI=1.231-7.076, p=0.015 and HR=1.873, 95% CI=1.528-6.642, p=0.018, respectively).
Conclusions
In this study CS, OTS and ES were the most common subtypes of PM BS, as expected according to literature. 2-year PFS was 63% and 2-year OS was 84%. GCT and OTS had improved OS compared to other subtypes. Elevated LDH at diagnosis and mitotic count (> 19 mitoses/HPF) were both predictors of mortality.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.