Two-Decade Trends in Radiotherapy Patterns and Clinical Outcomes for Soft Tissue Sarcoma: A Nationwide Study in South Korea (2005-2023).

BACKGROUND: Soft tissue sarcoma (STS) is a rare malignancy with increasing utilization of advanced radiotherapy (RT). We evaluated nationwide transitions in RT patterns and clinical outcomes for STS in South Korea, focusing on the impact of national healthcare policies. METHODS: Utilizing the National Health Insurance Service database (2005-2023), we identified 52,245 patients with STS. Temporal trends in RT modalities (3D-conformal RT [3D-CRT] vs. intensity-modulated RT [IMRT]) and fractions per course were analyzed using joinpoint regression with a pre-specified breakpoint at 2014. Survival analysis was performed for 45,465 patients using Cox proportional hazards models. RESULTS: The annual incidence of STS increased from 2338 to 3066 cases. A definitive shift toward IMRT occurred following the 2015 insurance expansion; by 2023, IMRT utilization reached 17.5%, while 3D-CRT declined to 0.3%. A sharp increase in mean fraction count was identified in 2012, with mean fractions rising from < 8 to > 16, indicating a marked shift in fractionation practice. In survival analysis, RT groups showed higher hazard ratios (HRs) for mortality (3D-CRT: 1.24; IMRT: 1.32), reflecting confounding by indication where RT was reserved for high-risk patients. However, in the non-surgery subgroup, IMRT was associated with a lower mortality risk than 3D-CRT (HR 1.20 vs. 1.25). Similarly, in pediatric patients, IMRT demonstrated a lower HR compared with 3D-CRT (3.35 vs. 4.19). CONCLUSION: RT for STS in Korea has transitioned to an IMRT-centered paradigm, catalyzed by supportive insurance policies. In non-surgery and pediatric cases, IMRT showed a lower HR than 3D-CRT, though this hypothesis-generating finding does not establish a survival benefit.