Prospective feasibility study of diagnostic CT-based simulation-free palliative radiotherapy

Conventional radiotherapy (RT) workflows require planning computed tomography (pCT) and treatment planning. However, these processes often take several days, leading to delays in RT initiation. Simulation-free radiotherapy (SFRT), which uses diagnostic CT (dCT) instead of pCT for treatment planning, may reduce the time from consultation-to-treatment delivery. However, the number of prospective studies conducted in Japan remains limited. This study prospectively evaluated the feasibility of SFRT in Japan. A single-center, single-arm prospective study (UMIN000054721) was performed in June 2024. This study included patients with vertebral metastases who were eligible for a single 8-Gy fraction. A dCT acquired within the last 56 days, without an immobilization device, and with an identifiable lesion, was required. The primary endpoint was the RT completion rate. The secondary endpoints included time in center (TIC), time from entering the consultation room to radiation beam-off, pain response and adverse events (AEs) at 4 and 12 weeks. Cone-beam CT (CBCT) verification was mandatory for patient setup. Five patients with six vertebral sites were enrolled. The RT completion rate was 100%. The mean TIC was 45 (range: 34-54) min. At 4 weeks, 25% of the patients presented with complete and partial pain responses. At 12 weeks, the complete response rate was 33%. None of the patients developed acute AEs. With appropriate patient selection and CBCT-guided verification, SFRT was feasible and safely implemented at a Japanese community hospital. Clinical trial registration: UMIN-CTR: UMIN000054721.