KEY POINTS
- This consecutive retrospective feasibility series included 11 patients receiving 12 VMAT lattice radiotherapy courses between October 2024 and March 2026. Treatment was considered when HCC exceeded 300 cm³ or tumor-to-liver or tumor-to-organ-at-risk geometry made SBRT or homogeneous curative-dose RT impractical.
- These were genuinely bulky and advanced tumors: 73% of patients had BCLC stage C disease, median baseline target volume was 556.5 cm³, and individual tumors ranged from 300 to 2,150 cm³. Eligible patients had ECOG 0–2 and Child-Pugh A to B7.
- Each treatment used 6–24 intratumoral lattice spheres, generally 1.5 cm in diameter. Spheres received 18–20 Gy on day 1, followed by individualized peripheral tumor irradiation of 20–52.5 Gy in 5–15 fractions; 37.5 Gy in 15 fractions was the most common peripheral prescription. Median peak-to-valley dose ratio was 3.32.
- At approximately three months, the median relative target-volume reduction was 64.6%, equivalent to a median absolute reduction of 320 cm³. Objective response was reported after all 12 treatment courses, and four complete responses were subsequently observed.
- At a median follow-up of only 6.1 months, all 12 treated targets remained locally controlled with no documented in-field progression. Radiographic regression was frequently accompanied by marked necrotic change, although residual enhancing tumor could remain at tumor–organ-at-risk interfaces where peripheral dose had intentionally been constrained.
- Rapid anatomical change was clinically relevant during treatment itself: 4 of 12 courses required adaptive replanning after daily high-resolution CBCT demonstrated changes that could compromise target coverage or organ-at-risk safety. The authors propose early adaptation checkpoints when substantial tumor shrinkage or loss of tumor–OAR clearance occurs.
- Acute adverse events were limited to grade 0–2 and caused no treatment interruption. Among 11 evaluable courses, one grade 3 radiation-induced liver disease event occurred and 10 had grade 0 RILD; no late toxicity had been recorded at available follow-up. Median overall survival was 6.2 months and median progression-free survival 6.0 months, but these outcomes are heavily confounded by advanced disease and concurrent or sequential systemic treatment.
CLINICAL TAKEAWAY
A median 65% reduction in tumors averaging more than half a liter in volume is an impressive feasibility signal, especially when homogeneous ablative treatment was considered unsafe. But 12 courses, six months of median follow-up and extensive concurrent multimodality therapy make efficacy impossible to isolate; the strongest conclusion is that VMAT lattice treatment appears deliverable and can produce rapid cytoreduction in carefully selected bulky HCC.