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Abstract

Purpose/objective

We propose a novel lattice deployment for spatially fractionated radiotherapy (SFRT) treatments. In this approach, a larger diameter high-dose sphere is centrally placed in the bulky tumor mass and surrounded by smaller diameter high-dose spheres.

Materials/methods

Thirty SFRT patients (10 head and neck [HN], 10 abdominal/pelvis, and 10 chest/lung cases) treated with an MLC-based crossfire method were retrospectively analyzed. Eleven differential hole-size lattice patterns were benchmarked against the clinically delivered SFRT plans (1 cm diameter cylinders, 2 cm spacing) and the standard uniform lattice pattern (1.5 cm diameter spheres, 3 cm spacing). These patterns varied in core diameter (C: 2–4 cm), spacing (S: 2–4 cm), and peripheral diameter (P: 1–2 cm). In addition to peak-to-valley-dose ratio (PVDR), tumor dose metrics (D50%, V50%, Dmean), Dmax to nearby critical organs, and ablative dose (V75%/V50% and V15Gy) were evaluated.

Results

10 out of 11 differential hole-size patterns showed increases in D50%, Dmean, and V50% compared to the standard lattice pattern. One pattern (C = 3 cm, S = 2 cm, P = 1.5 cm) outperformed the clinical SFRT plans in D50% (Δ = 1.8 Gy, p = 0.003; Δ = 2.0 Gy, p = 0.015; Δ = 0.9 Gy, p = 0.045), Dmean (Δ = 1.6 Gy, p = 0.003; Δ = 1.7 Gy, p = 0.021; Δ = 0.7 Gy, p = 0.042), and V50% (Δ = 20.4%, p <  0.001; Δ = 16.6%, p = 0.008; Δ = 10.3%, p = 0.079) for the HN, abdominal/pelvis, and chest/lung SFRT patients, respectively. This pattern also demonstrated average increases to D5% D10%, D90% across all 30 patients compared to both benchmarked patterns. However, this pattern showed reduced PVDR compared to the clinical and standard SFRT plans but still achieved a ratio > 3.0. All differential hole-size patterns demonstrated decreases in Dmax to critical organs compared to the clinical SFRT plans. Moreover, compared to the clinical SFRT and the standard lattice plans, 9 out of 11 differential hole-size patterns demonstrated increases in V75%/V50% and V15Gy.

Conclusion

All differential hole-size SFRT replans were clinically acceptable, with C = 3 cm, S = 2 cm, and P = 1.5 cm providing the optimal setting for select tumors. Differential lattice patterns enhanced the ablative dose to the bulky tumors while restricting the maximum dose to adjacent critical organs.

Document Type

Article

Publication Date

2025

Notes/Citation Information

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2025 The Author(s). Journal of Applied Clinical Medical Physics published by Wiley Periodicals, LLC on behalf of The American Association of Physicists in Medicine.

Digital Object Identifier (DOI)

https://doi.org/10.1002/acm2.70127

Funding Information

University of Kentucky, Markey Cancer Center’s Pilot Project, Grant/Award Number: P30 CA177558

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