Plaque brachytherapy for choroidal melanoma: strategies and techniques to reduce risk and maximize outcomes

ABSTRACT

Introduction

Plaque brachytherapy has become the most common eye and vision sparing treatment for uveal melanoma. This review explores methods to maximize vision retention, local tumor destruction and metastasis-free survival. Revealed are how medical physics and radiation therapy techniques have been used to improve outcomes and minimize risk. Attention was given to plaque selection based on intraocular radiation distribution, tumor size and intraocular location. Pre-treatment dosimetry-based plaque selection (e.g. palladium-103, ruthenium-106, iodine-125, strontium-90) offers an effective way to maximize vision and improve local control.

Areas covered

Historical comparisons show how plaque size and isotope selection affect intraocular radiation distribution. Contrasts are made with respect to radiation plaque-source selection. Ocular anatomy-driven management strategies are reviewed for iris, ciliary body, choroid and peripapillary uveal tumors. Methods are described to optimize surgical plaque implantation. Finger’s slotted plaque design is shown to overcome epibulbar obstructions; thereby normalizing episcleral plaque position.

Expert opinion

Expert opinions include how knowledge of normal tissue tolerances, customized plaque construction and standardized outcome measures can be used to improve local control and vision outcomes. SORRT, an ongoing multicenter, international radiation side-effects registry will be mined to compare and contrast radiation sources, improve our knowledge about plaque selection and patient outcomes.

KEYWORDS:

• Radiation
• brachytherapy
• plaque
• physics
• guidelines
• palladium-103
• ruthenium-106
• iodine-125
• strontium-90
• anti-VEGF

Article highlights

• Radioactive ophthalmic plaques have evolved from solid encapsulated, high-energy cobalt-60 discs to beta sources and then to shielded, low energy, modulatable gold seeded devices.

• Plaque construction and design affects ocular radiation distribution. Knowledge of plaque design reduces risk of local treatment failure.

• Pre-treatment radiation dosimetry simulating all available sources should be used to guide plaque selection.

• The American Brachytherapy Society - American Association of Physicists in Medicine Consensus Plaque Guidelines define optimal plaque position as covering the entire tumor and free-margin within the targeted zone.

• Slotted, seeded eye plaques can be used to overcome the optic nerve sheath obstruction in treatment of tumors near, touching and covering the optic disc.

• The cornea and sclera are relatively radiation resistant, the lens is replaceable and radiation vasculopathy (though anti-VEGF suppressible) remains a leading cause of severe irreversible blindness after ophthalmic radiation therapy.

• Anti-VEGF therapy has been shown to suppress radiation maculopathy and optic neuropathy.

Acknowledgments

John J Munro III, Ph.D. performed a critical review of this manuscript. Dr. Ankit Singh Tomar helped analyze the plaque data. My first mentor, Samuel Packer MD started me on the path to learn about medical physics and radiation as it relates to ophthalmic oncology.

Declaration of interest

Paul Finger is Director of The New York Eye Cancer Center, CEO of The Eye Cancer Foundation, Inc. and LV Liberty Vision. The author has no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose

Additional information

Funding

Manuscript has been funded by The Eye Cancer Foundation, Inc. (http://eyecancercure.com)