Radioactive Plaque Brachytherapy for Ocular Tumours
- How is radiation therapy used in the management of intraocular tumours?
- What is a Radioactive Plaque?
- What are the current indications for Plaque Brachytherapy?
- How is a radioactive plaque used?
- How is the surgery performed?
- Is Plaque Brachytherapy available in India?
- What is the procedure for patient referral?
How is radiation therapy used in the management of intraocular tumours?
For over 100 years or longer, the usual treatment for intraocular tumours has been enucleation. Since World War II, various forms of radiation have been used in the management of Retinoblastoma and Melanoma, the more common intraocular tumours. During the past three decades, this treatment has been refined to produce optimal results.
Radiation at the appropriate dose rates and in proper physical forms is intended to eliminate tumour cells without causing anatomical or functional damage to the normal ocular tissues.
External beam Radiation therapy has the disadvantage of delivering radiation to the surrounding structures as well, resulting in short term and long term morbidity. The most successful method for irradiating medium-sized tumours involves the use of a radioactive plaque.
What is a Radioactive Plaque?
A radioactive plaque is a device that can be used to give a high dose of radiation precisely and selectively to a tumour and a negligible dose to the surrounding structures. It is constructed using Radioactive Cobalt, Ruthenium, Iridium, Palladium or Iodine sealed within. Plaques come in various shapes and sizes ranging from 10m to 25mm in diameter.
What are the current indications for Plaque Brachytherapy?
- Retinoblastoma measuring <16mm in basal diameter and <8mm in thickness as primary treatment, as an adjunct to chemoreduction, and for failure of focal therapy.
- Primary treatment for most medium-sized and some large choroidal and ciliary body melanomas in an eye with salvageable vision.
- Choroidal Hemangioma
- Choroidal Metastasis
- Extensive retinal capillary Hemangioma
How is a radioactive plaque used?
The intraocular tumour is assessed for its location, height and diameter by a clinical examination and imaging. The radiation dose and exposure time are calculated by an automated dosimetry software and an appropriate plaque is selected. This process needs the expertise of a radiation therapist and a radiation physicist well versed in Brachytherapy.
How is the surgery performed?
The surgery is performed under general anesthesia in children and local anesthesia in adults. The patient stays in the hospital under strict radiation safety precautions for the duration of the radiation exposure, after which the plaque is removed. The surgery for plaque removal is a short, simple procedure and often the patient can go home later the same day.
The effects are periodically assessed every 6 weeks to 3 months until there is complete regression. The results of plaque brachytherapy have generally been favorable. The rate of tumour control is 80-90% in Retinoblastoma and 60-80% in Melanoma. Complications include Dry-eye, cataract, radiation retinopathy, radiation paillopathy, and rarely, visual loss.
Is Plaque Brachytherapy available in India?
The Ocular Oncology Service at the LV Prasad Eye Institute is the first facility in India to be approved by the Radiological Safety Division of the Atomic Energy Regulatory Board, and the Bhabha Atomic Research Centre, Government of India, to use to plaque brachytherapy in the management of intraocular tumours.
The radioactive source Ruthenium-106 (a beta-emitter with a half-life of 368 days) has been acquired from the BEBIG Isotopen und Medizintechnik GmbH, Germany.
A workstation running plaque stimulator dosimetry software has been installed and the radioactive plaque brachytherapy facility at the LV Prasad Eye Institute is now operational for patient treatment.
What is the procedure for patient referral?
The Ocular Oncology Service evaluates patients for plaque brachytherapy every Tuesday and Friday.
Considering the need for expeditious diagnosis and management of ocular tumour, we do not require new patients referred to the Ocular Oncology Service to have a prior appointment. Where possible, an appointment maybe taken in advance by contacting the Patient Care Services.