Feasibility planning study of lattice radiotherapy for palliation in bulky tumors.

Purpose: Lattice radiotherapy can potentially deliver high doses to the tumor core, while conventional doses to the periphery resulting in improved response rates in large tumors (> 5 cm). We assessed the feasibility of planning lattice radiotherapy and dosimetrically compared it with conventional radiotherapy.

Methods: This retrospective dosimetric study evaluated 10 patients with large tumors (> 5 cm) treated with palliative intent with a dose of 20Gy in five fractions. High-dose lattice points were created at doses of 50Gy in non-hepatic tumors and 35Gy in hepatic tumors. Lattice plans were compared with treatment plans regarding dose coverage and organ-at-risk dosimetry.

Results: Treated sites included soft tissue metastases to the neck, lungs, abdomen, pelvis, and liver. The mean lesion volume was 1103 cc (352-3173 cc). The maximum tumor size was 16 cm. The target volume coverage was > 95% in all but one case (88% to achieve organ constraints). Dosimetry and organ-at-risk doses were similar in both palliative treatment and simulated lattice plans.

Conclusion: Lattice radiotherapy is feasible in large tumors using volumetric-modulated arc therapy and achieves good coverage while meeting organ constraints. However, a prospective clinical evaluation is required to confirm its efficacy.