# PTCOG Ocular Survey – Perspective on Ocular Particle Therapy: Current Practices and Emerging Trends

## TL;DR

This survey provides an overview of current practices and future trends in ocular particle therapy, highlighting the need for standardization and technological updates.

## Contribution

The paper presents the first international survey on ocular particle therapy practices and trends, emphasizing standardization and technological challenges.

## Key findings

- Twenty facilities worldwide offer ocular particle therapy, primarily using dedicated horizontal beamlines.
- Adoption of high-energy general-purpose beamlines is increasing, but requires evaluation of dosimetric and clinical impacts.
- Common dosimetry protocols exist, but variability in planning and quality assurance remains a challenge.

## Abstract

To overview the status and trends in the current rapidly evolving field of ocular particle therapy (OPT).

The Particle Therapy Co-Operative Group Ocular Subcommittee developed an online survey, including 127 questions, made available to treatment centers worldwide, between April 2022 and January 2024. The survey covered a broad range of topics from general program organization and beamline description, to diagnoses and patient numbers treated, treatment planning and set-up, quality assurance techniques, as well as insights into anticipated future developments.

Twenty facilities offered OPT by the end of 2023: 3 in Asia, 9 in Europe, and 8 in the USA. Combined, they treated, on average, 1800 patients per year, with uveal melanoma being the most common indication. The vast majority of treatments continue to be delivered on dedicated horizontal beamlines, both high (>120 Mev) and low (<75 MeV) energy. Five of the 7 recently established programs (n = 7, since 2015) use high-energy general-purpose beamlines, where some beam characteristics, including penumbrae size and dose delivery rate, differ from those typically achieved on dedicated beamlines. The evolution of the ocular treatment framework is ongoing as 9 centers reported the intent to upgrade their systems within five years, to engage state-of-the-art developments in beam delivery, imaging, and planning tools.

Common protocols in dosimetry, dose, and fractionation have largely been adopted worldwide, while variability persists in planning, quality assurance, and delivery workflows. The obsolescence of dedicated ocular proton systems and key planning tools, and a lack of standardization, remain as pressing challenges. The adoption of non-dedicated high-energy systems on gantries and integration into multipurpose treatment environments enhances OPT accessibility, but this transition requires ongoing critical evaluation of dosimetric trade-offs and clinical outcomes. Multicenter collaboration, technological innovation, and clinical validation are essential to continued assurance of the safe and effective delivery of OPT worldwide.

•International survey results on ocular particle therapy (OPT) are presented.•Variability in planning and quality assurance highlights a need for standardization.•Adaptation of high-energy systems broadens access but requires clinical follow-up.•The obsolescence of beam generation and planning systems remain pressing challenge.•Collaboration and technical advances are essential to OPT sustainability and growth.

International survey results on ocular particle therapy (OPT) are presented.

Variability in planning and quality assurance highlights a need for standardization.

Adaptation of high-energy systems broadens access but requires clinical follow-up.

The obsolescence of beam generation and planning systems remain pressing challenge.

Collaboration and technical advances are essential to OPT sustainability and growth.