Palladium-103 Radiation Effective for Small Choroidal Melanoma

June 25, 2013

By Will Boggs, MD

NEW YORK (Reuters Health) Jun 25 - Palladium-103 plaque radiation therapy was effective for treating small choroidal melanomas in a retrospective study.

Based on the results, early intervention with palladium-103 plaque therapy may be associated with "excellent local control, more acceptable vision retention, and a very low risk of metastatic disease," Dr. Paul T. Finger from The New York Eye Cancer Center, New York told Reuters Health.

It's time, Dr. Finger said, to "reassess our methods of radiation source selection away from the dogmatic use of iodine-125 seeds or ruthenium-106 plaques to that based on comparative dosimetry, local control, and vision retention data. Such has been the recommendation of the American Association for Physicists in Medicine."

Dr. Finger and Dr. Ekaterina Semenova used palladium-103 plaque radiation therapy in 72 patients with stage T1a choroidal melanomas between 1.5 and 2.4 mm in apical height and up to 10 mm in largest basal dimension. All pretreatment metastatic surveys were negative.

The mean follow-up was 54 months, as reported June 17th online in Ophthalmology.

Mean tumor thickness gradually regressed over time, even beyond three years after irradiation, and local tumor control was achieved in all patients. No one developed metastatic disease.

As of the last examination, final vision was improved in 15 patients (20.8%), unchanged in 35 (48.6%), and decreased in 22 (30.6%). Visual acuity of 20/200 or better was preserved in 68 of 72 patients (94.4%).

Long-term complications included radiation maculopathy (31/72, 43.1%) and radiation optic neuropathy (15/72, 20.8%). Twelve patients (16.7%) had both complications, but 38 patients (52.8%) were complication-free.

After the advent of anti-VEGF therapy for radiation retinopathy, 20 patients with radiation-related maculopathy or optic neuropathy received periodic intravitreal anti-VEGF therapy. Six of these improved by a mean of one line, and 10 maintained their pretreatment visual acuity after a mean combined duration of anti-VEGF treatment of 22 months (range, 4-62 months).

There were no cases of anterior segment neovascularization or secondary glaucoma, and no eyes were enucleated for radiation complications.

At The New York Eye Center, palladium-103 is preferred for most cases, independent of tumor size, but particularly for small uveal melanomas, Dr. Finger said.

"However, it is my hope that when treatment is considered warranted, each center should perform comparative dosimetry (palladium-103, iodine-125, ruthenium-106)," Dr. Finger said. "That is, a comparison of radiation dose to tumor, fovea, optic nerve, lens and opposite eye wall. Then pick the 'best' radionuclide source for each patient (based on those comparisons)."

"Of note," Dr. Finger added, "increased radiation dose to fovea and optic nerve has been shown to be most closely related to long-term vision loss. Unfortunately, a comparison to protons (charged particles) is not that simple due to high dose rate and entry dose effects."

SOURCE: http://bit.ly/1abHefK

Ophthalmology 2013.

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