Tumour volume as a predictor of metastases in patients presenting with high-grade conventional osteosarcoma of the extremities

Background: The aim of this study was to compare the initial tumour volume in patients with and without pulmonary and/or skeletal metastases at time of presentation. The secondary aim was to compare the value of tumour volume in the prediction of metastases at time of presentation with known predictive factors, namely serum alkaline phosphatase (ALP) and lactate dehydrogenase (LDH). Materials and methods: A retrospective cross-sectional analysis was performed comparing the primary tumour volume in patients with and without metastases. All patients with histologically confirmed high-grade conventional osteosarcoma over a five-year period were included. Results: The study comprised 61 patients. The mean age was 21 years (SD: 11.9, range 5–56) with an equal distribution of males and females (51% vs 49%). There was no correlation between tumour volume and age at presentation (p=0.31). There was no evidence of metastases in only 20% (n=12) of patients. Skeletal metastases were present in 28% (n=16) of the patients and pulmonary metastases were present in 44 cases (72%). There was no significant difference in the tumour volume at presentation beteen patients with and without pulmonary metastases (p=0.11). However, tumour volume did appear to predict the presence of skeletal metastases (p=0.02). A tumour volume of 1 383 cm³ had a negative predictive value (NPV) of 92% and positive predictive value (PPV) of 55% for the presence of skeletal metastases (area under curve [AUC]=0.76; sensitivity 66%; specificity 87%). A tumour volume of 480 cm³ had a 100% NPV for the presence of skeletal metastases (AUC=0.74). A tumour volume ≥1 380 cm³ had an odds ratio (OR) of 13.6 (p<0.01; 95% CI 2.6–72.5) as an independent variable in relation to skeletal metastases. Multivariate analysis (with ALP and LDH) of tumour volume ≥1 380 cm³ yielded an OR of 8.6 (p=0.04; 95% CI 1.1–67) for presence of skeletal metastases. Conclusion: In this series of conventional high-grade osteosarcoma of the extremities, we found a very high rate of metastases at time of diagnosis. While there was no association with pulmonary metastases, increased tumour volume was associated with an increased risk for the presence of skeletal metastases. More studies in the developing world clinical setting are required to investigate this further; the high rate of metastases seen at time of diagnosis also requires further investigation. Level of evidence: Level 4