Bone and soft tissue sarcoma mortality in 19 811 patients diagnosed in Japan, 2006-2020

BACKGROUND: Sarcomas are rare malignant tumors with heterogeneous histologies and limited population-based evidence. Although new treatments have been introduced in recent years, their effect on real-world survival outcomes remains unclear. This study aimed to evaluate recent trends in mortality for bone and soft tissue sarcomas in Japan. METHODS: We conducted a cohort study using data from the Bone and Soft Tissue Tumor Registry, a nationwide database maintained by the Japanese Orthopaedic Association. Patients diagnosed with primary sarcomas between 2006 and 2020 were included and grouped by diagnostic period (2006-2010, 2011-2015, 2016-2020). The primary outcome was cumulative mortality risk, estimated using Poisson regression. Subgroup analyses were conducted by age, sex, tumor origin, metastasis status, treatment modality, and histological subtype. Sensitivity analyses included multiple imputation, Kaplan-Meier estimates, and competing risk models. RESULTS: A total of 19 811 patients were analyzed. No statistically significant change in overall mortality risk was observed across diagnostic periods. Ewing sarcoma showed a consistent decline in mortality, whereas other subtypes did not. Mortality risk was lower in patients who received surgery and higher in those who received radiotherapy or chemotherapy. Results were robust across sensitivity analyses. CONCLUSIONS: Survival outcomes for sarcoma patients in Japan have remained largely unchanged over the past 15 years, except for Ewing sarcoma. Novel therapeutic approaches are needed to achieve meaningful improvements in prognosis.