VMAT-based lattice radiotherapy for advanced bulky hepatocellular carcinoma within multimodality treatment: a consecutive feasibility series

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Purpose Bulky advanced hepatocellular carcinoma (HCC) remains difficult to treat with conventional homogeneous ablative radiotherapy because safe dose escalation is limited by hepatic reserve, tumor-to-liver geometry, and adjacent organs at risk (OARs). This study evaluated local control, tumor response, toxicity, and treatment continuity after volumetric-modulated arc therapy (VMAT)-based lattice radiotherapy (VMAT-LRT) in patients with advanced HCC. Methods We retrospectively reviewed our initial consecutive VMAT-LRT cohort treated between October 2024 and March 2026. VMAT-LRT was considered for tumors >300 cm 3 or unfavorable tumor-to-liver or tumor-to-OAR geometry that rendered SBRT or homogeneous curative-dose radiotherapy unfeasible, while local treatment remained indicated. VMAT-LRT delivered high-dose intratumoral lattice spheres using VMAT-based planning, followed by lower-dose peripheral irradiation individualized according to clinical goals. Endpoints included local control, tumor response, RILD, CTCAE toxicity, and treatment continuity. Results Twelve VMAT-LRT courses in 11 patients were completed as planned. Median age was 70 years, median follow-up was 6.1 months, and median initial tumor volume was 557 cm 3 . Objective tumor response was observed in all treated courses. Median relative and absolute volume reductions were 65% and 320 cm 3 , respectively. Local control was achieved in all courses, with no documented local progression. Four patients achieved complete response. Systemic or subsequent anticancer therapy continued after radiotherapy in 8 of 11 patients without interruption attributable to acute radiotherapy-related toxicity. Acute toxicity was limited to Grade 0–2 events. RILD was Grade 0 in 10 evaluable courses and Grade 3 in one course. No late toxicity was recorded among 11 evaluable courses. Conclusion VMAT-LRT was feasible for advanced bulky HCC, achieving meaningful tumor regression and durable in-field local control with acceptable toxicity while allowing continuation of multimodality treatment in selected patients.