Long-Term Observation of the Epidemiology and Survival of Osteosarcoma in a Rural Area of Japan

Objectives: No definitive risk factors for osteosarcoma have been identified. To assess regional differences, it is essential to minimize racial and other biases. However, few studies have examined this issue with minimal bias. This study aimed to evaluate regional variations in the incidence and characteristics of osteosarcoma in a rural prefecture with limited population mobility within ethnically homogeneous Japan. Subject and Methods: We retrospectively identified 40 patients with primary osteosarcoma who received treatment at our hospital from 2000 to 2024. Clinical data were collected. Akita City, the prefectural capital and most populous city in Akita Prefecture, was compared with other cities, towns, villages, and regions regarding incidence and prognosis. We also examined poor prognostic factors across all cases. Results: The incidence rate in Area 2 was significantly higher than that in Area 1 (P = 0.0269). Across municipalities, Oga City in Area 2 and Yuzawa City in Area 5 exhibited significantly higher incidence rates than Akita City (P = 0.0243 and P = 0.0477). Kaplan-Meier analysis comparing the prognosis of Area 1 with Areas 2 and 5 showed that only Area 2 had a significantly worse prognosis than Area 1. Univariate analysis of prognostic factors demonstrated that surgical treatment was the sole factor associated with improved prognosis. Conclusion: These findings suggest the existence of regional differences in the incidence and characteristics of osteosarcoma.