Comparison of the clinical outcomes and prognostic factors of dedifferentiated chondrosarcoma and chondroblastic osteosarcoma: a population-based analysis

Background Dedifferentiated chondrosarcoma (DDC) and chondroblastic osteosarcoma (COS) have some common morphological characteristics by pathology and involve the same surgical methods and chemotherapy regimen. We explored the prognostic differences and factors of patients with DDC and COS with similar pathological features to analyze the prognostic factors and effect of chemotherapy on the prognosis of each type. Methods From the SEER database, we included 228 patients with DDC and 631 patients with COS who underwent surgery from 1975 to 2016. Patient age was stratified with X-tile, and prognosis was analyzed by the Kaplan-Meier method and Cox proportional hazard regression. Results The 3- and 5-year overall survival (OS) rates for DDC were 33.3% and 26.5%, respectively, and the 3- and 5-year OS rates for COS were 71.5% and 63.8%, respectively. Compared with COS, DDC had an older onset age, a higher proportion of white patients, an increased likelihood of occurrence in soft tissue, a higher pathological grade, a larger tumor volume, more patients with M1-stage, a higher AJCC stage and a lower chemotherapy utilization rate. Univariate analysis showed that age, M1 stage and high tumor stage were negatively correlated with DDC patient prognosis, with a worse prognosis for patients with lung metastasis. In the multivariate analysis, higher tumor stage was an independent factor for reducing OS in DDC. Univariate analysis showed that COS patients were older and male; had tumors located in the pelvis; had high T-, M-, and AJCC-stage tumors; and had lung metastasis. Moreover, no chemotherapy was negatively correlated with patient prognosis. Furthermore, age, male sex and high tumor stage were independent factors for reducing OS in COS. Conclusion The OS of DDC patients is worse than that of COS patients. Chemotherapy cannot benefit patients with DDC. For COS patients, further exploration of the survival benefits of chemotherapy is needed.