Plaque radiotherapy (brachytherapy) for choroidal melanoma – pro
Plaque radiotherapy is a different procedure than photocoagulation. Plaque brachytherapy is a widely accepted alternative to enucleation for medium-sized posterior uveal melanomas (<10 mm in height and <15 mm in diameter). The most common material used in modern plaques is iodine 125, because of its lower energy emission (lack of alpha and beta rays), its good tissue penetration, and its commercial availability. Radiation from this source causes tumor destruction through damage of DNA in cancerous cells and tumor vessels, with consequent tumor necrosis and regression. However, it is not devoid of complications. Plaque brachytherapy can cause complications, including cataract, rubeosis, scleral necrosis, keratopathy, radiation retinopathy, and optic neuropathy, but at a reduced rate compared with external beam irradiation.
Usually 10 mm or smaller is the appropriate sze of melanomas for this procedure. However, the American Brachytherapy Society’s guidelines state: “..some patients with large melanomas (>10 mm height or >16 mm basal diameter) may also be candidates.”
Previous publications have found several tumor features to correlate with increased mortality, including larger size, anterior location, transscleral extension, growth through the Bruch membrane, optic nerve extension, lack of pigmentation, and histologic characteristics (eg, mitotic activity and cell type). Although metastases from the primary intraocular melanoma can first be detected years later, their highest incidence is in the first year after diagnosis. There are no studies showing effectiveness of any kind of followup. As yet, no effective treatment exists for metastatic uveal melanoma and it is not certain that eraly diagnosis affects ultimate prognosis. As such, surveillacne cannot be recommended.
Eye plaques are individually designed and constructed for each patient. The precise distribution of radiation throughout the eye is calculated and used to determine the risks of secondary radiation complications. Because there si potential radiation exposure to others, laws regulate length of stay. Depending on the radiation laws of the state in which treatment is given, a patient may be required to stay in the hospital for the entire length of treatment(around 5 days). In any case, it is reasonable precaution.
REFERENCES:
Boldt HC, Melia BM, Liu JC, Reynolds SM; Collaborative Ocular Melanoma Study Group.
I-125 brachytherapy for choroidal melanoma photographic and angiographic abnormalities: the Collaborative Ocular Melanoma Study: COMS Report No. 30.Ophthalmology. 2009 Jan;116(1):106-115.e1.
Thomas Riley O.D. et al, Treatment options for choroidal malignant melanoma: a case report featuring transpupillary thermotherapy Optometry – Journal of the American Optometric Association
Volume 75, Issue 2, February 2004, Pages 103-114
American Brachytherapy Society recommendations for brachytherapy of uveal melanomas.Int J Radiat Oncol Biol Phys. 2003 Jun 1;56(2):544-55. .
I-125 brachytherapy for choroidal melanoma photographic and angiographic abnormalities: the Collaborative Ocular Melanoma Study: COMS Report No. 30.Boldt HC, Melia BM, Liu JC, Reynolds SM; Collaborative Ocular Melanoma Study Group.Ophthalmology. 2009 Jan;116(1):106-115.
Thomas Riley O.D. et al, Treatment options for choroidal malignant melanoma: a case report featuring transpupillary thermotherapy Optometry – Journal of the American Optometric Association
Volume 75, Issue 2, February 2004, Pages 103-114