Phaco Training: Radioactive Plaque Brachytherapy

By | February 4, 2015
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Radioactive Plaque Brachytherapy for Ocular Tumors

 

About plaque brachytherapy

 

 
  How is radiation therapy used in the management of ocular tumors? For over 100 years or longer, the usual treatment of intraocular tumors has been enucleation. Since World War II, various forms of radiation treatment have been used in the management of retinoblastoma and melanoma, the most common malignant primary intraocular tumors in children and adults respectively. During the past 3-4 decades, the technique of radiotherapy has been refined to produce optimal results with minimal collateral damage.Radiation is intended to eliminate proliferating tumor cells without causing anatomical or functional damage to normal ocular structures. While using radiation to treat tumors of the eye, the goal is to destroy the tumor, save the eye, and maximise visual potential. To be able to do so, it is necessary to provide high dose of radiation to the tumor, while preventing exposure to rest of the normal ocular structures. Radioactive plaque brachytherapy does this with finesse and precision. 
 
 
  What is a radioactive plaque?

 

A radioactive plaque is a device that can be used to deliver therapeutic dose of radiation precisely and selectively to a tumor and negligible radiation to the surrounding normal structures.

 

It is constructed using radioactive Cobalt, Ruthenium, Iridium, Palladium or Iodine. Of these, Ruthenium (Ru106) and Iodine (I125) are most popular. Plaques come in several useful shapes and sizes. 
 
 
  How is radioactive plaque used?

 

The intraocular tumor is measured for its exact location, height and basal diameter by clinical evaluation and imaging. Radiation dose and exposure time are calculated by an automated dosimetry software. The process needs the expertise of a radiation oncologist and a physicist well-versed with brachytherapy.
 
 
  Is plaque brachytherapy available in India?

 

Dr Santosh G Honavar along with Dr Vijay Anand Reddy initiated plaque brachytherapy for the first time in India over 12 years ago and their team has the largest experience in this field.

 The Ocular Oncology Service at the Centre for Sight, Hyderabad is specifically approved by the Atomic Energy Regulatory Board, Government of India to procure radioactive isotopes and perform the procedure.

 The radioactive source Ruthenium-106 has been acquired from BEBIG Isotopen and Medizintechnik GmbH, Germany.
How is the surgery performed?
The surgery is performed under local or general anesthesia. Conjunctival  peritomy is performed  in the concerned quadrant. The tumor is localized by a combination of intraoperative indirect ophthalmoscopy and transillumunation and confirmed using transscleral laser. The exact location of the tumor is marked on the sclera, the plaque is centered on the tumor and sutured to the sclera. The conjunctiva is then reposited back. The patient stays in the hospital under strict radiation safety precautions for the duration of radiation exposure, following which the plaque is removed. The patient goes home later the same day. The effect of plaque brachytherapy on tumor regression is periodically assessed every 8-12 weeks until complete regression.

 
What are the results of plaque brachytherapy?
Plaque brachytherapy has excellent success in tumor control with >90% eye salvage in retinoblastoma, melanoma, metastasis and lymphoma. It has nearly 100% success in choroidal hemangioma. The recent application in managing ocular surface squamous neoplasia and melanoma with scleral infiltration has met with spectacular success in eye and vision salvage.

The following ocular conditions can be treated with this modality:

Retinoblastoma

Iridocilary Melanoma

Amelanotic Choroidal Melanoma

Diffuse Choroidal Hemangioma

OSSN with Scleral Invasion (including squamous cell carcinoma)

Conjunctival Melanoma with Scleral Invasion