Harmonizing spatially fractionated radiation therapy: consensus and roadmap from an ESTRO workshop.

BACKGROUND AND PURPOSE: Spatially fractionated radiation therapy (SFRT) intentionally delivers nonuniform dose distributions characterized by alternating high-dose peaks and low-dose valleys, with therapeutic potential for complex, inoperable bulky tumors. Although clinical adoption is expanding, clinical implementation and practices remain heterogeneous across institutions. This consensus aims to identify system-level barriers to harmonized clinical implementation of SFRT and formulate consensus-based recommendations to enable reproducible multi-institutional integration.

METHODS

The 2025 ESTRO Physics Workshop convened multidisciplinary international experts to evaluate current implementation practices and develop harmonization priorities through structured consensus discussions. Twenty-eight delegates participated, representing centers across Europe, the United States, China, and Australia. Core domains included dose recording and reporting specifications, commissioning and quality assurance (QA), motion management, registry infrastructure, and governance.

RESULTS

Five principal domains were identified as barriers to harmonized implementation: (1) inconsistent dose recording and reporting conventions; (2) variability in commissioning and QA practices for heterogeneous small-field dose distributions; (3) uncertainty in motion management and geometric robustness evaluation in the presence of anatomical changes; (4) fragmented data infrastructure limiting multi-institutional outcome analysis; and (5) limited coordinated governance and standardization infrastructure. Consensus recommendations and a phased roadmap with measurable milestones were formulated to address these domains.

CONCLUSION

Harmonization of clinical implementation is essential to ensure reproducibility, support prospective multi-institutional trials, and safeguard consistent patient care across institutions. Coordinated international collaboration will be critical to establish standardized definitions, QA benchmarks, registry infrastructure, and governance frameworks for safe and effective clinical integration.