Abstract
BACKGROUND: Disease progression (DP) of osteosarcomas, albeit with aggressive treatments, hinders improving survival. The DP patterns are unique in low- and middle-income countries like South Africa. We determine the prognostic factors associated with disease progression (DP) of the appendicular skeleton's central high-grade conventional osteosarcoma (COS). METHODS: This is a retrospective study of 77 patients, with a minimum 3-year follow-up period diagnosed with histological biopsy-confirmed COS. Descriptive statistics, Cox proportional regression modelling, and the Kaplan-Meier method were employed for the analysis. RESULTS: DP occurred in 75 % of patients (58/77), either as a local progression - LP 32 % (25/77), systemic progression - SP 61 % (47/77) or both 32 % (24/77). In the univariate analysis, the factors associated with DP were proximal humerus tumor site (hazard ratio [HR] 2.48; 95 % confidence interval [CI], 1.02 to 6.04; p < 0.046), metastasis at diagnosis (HR 1.91; 95 % CI, 1.10 to 3.32; p < 0.022), multiple metastatic lesions (HR 2.58; 95 % CI, 1.13 to 5.88; p < 0.024), curative treatment (HR 0.33; 95 % CI 0.17 to 0.62; p < 0.001), palliative treatment (HR 2.17; 95 % CI 1.24 to 3.78; p < 0.007), and wide surgical resection (HR 0.48, 95 % CI 0.27 to 0.86; p < 0.013). On multivariate analysis, only age >19 years was an independent risk factor (HR 1.04; 95 % CI 1.00 to 1.08; p < 0.034). The median survival time was 24 months, with an overall survival (OS) of 57.1 % at 3 years. The projected Kaplan- Meier 5-year OS rate was 29.78 %, with a progression-free survival (PFS) rate of 10.28 % (HR 0.76; 95 % CI 0.52 to 1.112; p < 0.128). CONCLUSION: In this series of central high-grade conventional osteosarcoma of the appendicular skeleton from South Africa, we observed a uniquely high proportion of disease progression (DP). Age >19, metastatic disease, and no chemotherapy response yielded poor outcomes; in contrast, wide surgical resection is beneficial. Further elucidation is needed at a larger scale in this region. STUDY EVIDENCE LEVEL: IV.