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Vasileios Petousis, Kimberly J. Chin, Paul T. Finger; Palladium-103 Plaque Radiation Therapy of the Anterior Segment of the Eye: Treatment for Diffuse Iris Melanoma. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3408.
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To describe our methods and preliminary results of anterior segment palladium-103 (103Pd) radiation therapy for diffuse iris melanoma.
Interventional case series describing 3 eyes with FIT-biopsy proven multifocal iris melanoma. Each was treated with 103Pd plaques that included the entire anterior segment within the targeted zone. The cornea was protected with amniotic membranes during irradiation. Pre-operative comparative dosimetry was used to choose which radionuclide (125I versus 103Pd) would be included within each plaque. Assessed clinical outcomes included: visual acuity, secondary cataract and glaucoma, hemorrhage and recurrence. Clinical testing included EDTRS visual acuities, slit lamp and goniophotography as well as high frequency ultrasound (UBM) imaging. Data was obtained through chart review.
Pre-operative comparative dosimetry favored the use of 103Pd in all three cases. For example, for an equivalent tumor dose (mean 83.2 Gy to an average 2.5 mm from inner sclera, the use of 103Pd resulted in a % dose difference of 98% to the macula, 88% to the optic nerve, and 2% to the natural lens. The first patient has lost 3 lines of visual acuity due to cataract formation. However, the other two are pseudophakic. With a mean 6 months follow up, there have been no failures of local control, secondary neovascular glaucomas nor radiation keratopathy. There has been no radiation maculopathy nor optic neuropathy in this series. One patient developed neovascular glaucoma as a manifestation of his disease, found prior to anterior segment plaque radiation therapy. High frequency ultrasound imaging revealed a mean 9% reduction in tumor thickness. Serial abdominal imaging has revealed no metastatic uveal melanoma.
Plaque radiation therapy can be used as an alternative to enucleation for diffuse iris melanoma. We have shown that comparative dosimetry favors the use of 103Pd seeds compared to 125I for this purpose. When the treatment includes the entire anterior chamber within the target zone, complications such as secondary glaucoma, cataract formation and iris visualization must be considered. However, with relatively short follow up, we have noted no complications that might preclude the use of anterior segment plaque radiation therapy for diffuse iris melanomas.
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