3081 - Standardizing Lattice Radiotherapy for Prospective Clinical Translation

12:30pm - 01:45pm ET

Poster Hall - Exhibit Hall A

Screen: 29

POSTER

Presenter(s)

Jeremy Booth, PhD - Northern Sydney Cancer Centre, Marrickville, NSW

L. Moghaddasi¹, R. Bromley¹, S. Roderick², M. Back^1,3, S. Bergamin^2,3, S. Carroll^1,3, J. Chan¹, P. J. Horsley¹, G. Hruby¹, D. Jayamanne^1,3, A. Kneebone¹, G. M. Lamoury^1,3, G. Metz¹, M. L. Morgia¹, J. Booth^1,4, and T. N. Eade^2,3; ¹Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney, Australia, ²Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney, NSW, Australia, ³Sydney Medical School, University of Sydney, Sydney, NSW, Australia, ⁴Institute of Medical Physics, School of Physics, University of Sydney, Sydney, NSW, Australia

Purpose/Objective(s): Lattice radiotherapy (LRT) is supported by international trials but yet to be clinically implemented in Australia. We hypothesized that guideline-consistent LRT plans meeting institutional OAR constraints can be generated and delivered using existing clinical infrastructure. This study aimed to validate a standardized planning and QA framework in preparation for clinical translation.

Materials/Methods: To establish an institutional LRT planning and radiobiological framework in preparation for prospective clinical implementation, representative bulky (491–8235 cc), radioresistant tumors across thoracic (4), abdominal (7), and pelvic (4) sites were selected to test protocol robustness (11 patients, 15 plans). Planning followed published LRT guidance and trial-informed practice. Gross tumor volumes were contracted 5–10 mm to define lattice targets. Spherical vertices (1.5 cm diameter) were spaced 4–5.5 cm apart in alternating axial planes. VMAT plans using 6FFF or 10FFF beams were generated using a structured three-stage optimization strategy to achieve reproducible sharp vertex gradients. LRT-alone and LRT combined with conventional external radiotherapy (cERT) were developed to define protocol boundaries. Target plan quality metrics included equivalent uniform dose (EUD) and peak-to-valley dose ratio (PVDR). OAR evaluation required compliance with institutional clinical constraints. A radiobiological modeling framework was established and applied consistently to derive target and OAR EUD as biologically informed metrics for prospective outcome correlation. Accuracy of delivered dose was confirmed using EPID-based patient-specific QA with gamma analysis (3%/1mm).

Results: All plans achieved prescribed target coverage while demonstrating intended spatial modulation. Overall mean PVDR was 3.1±0.6. Site-specific analysis demonstrated mean PVDR values of 3.9 (thorax), 2.7 (abdomen), and 2.4 (pelvis).

Spatial modulation was consistently greater in LRT-alone plans, with PVDR values 34%–51% higher compared with LRT combined with cERT.

Institutional OAR dose constraints were met in all cases. Modeled OAR EUD averaged 1.3±0.5 Gy, corresponding to a mean survival fraction of 0.7±0.1, suggesting potential dosimetric advantage compared with GRID (0.3-0.5). Patient-specific QA confirmed accurate delivery of the heterogeneous dose distributions, with gamma pass rates >95% for all plans.

Conclusion: A structured institutional LRT planning and radiobiological modeling framework was successfully implemented across multiple bulky tumor sites. Reproducible spatial modulation, consistent derivation of target and OAR EUD, adherence to conventional OAR safety benchmarks, and verified deliverability demonstrate technical robustness within local infrastructure.

These findings establish quantitative dosimetric and biologically informed metrics to support prospective clinical trial participation and future evaluation of LRT outcomes.