Rare as it is, uveal melanoma–or cancer in the eye involving the iris, cilliary body, or choroid–is the most common primary cancer of the eye, according to the National Cancer Institute. Treatment of uveal melanoma is achieved with radiation therapy, although a variety of regimens and techniques have been applied successfully. A new retrospective study performed by researchers at Duke University, “Uveal Melanoma Treated with Iodine-125 Episcleral Plaque: An Analysis of Dose on Disease Control and Visual Outcomes,” identified 69 Gy of radiation applied at the tumor apex to be sufficient to control tumor growth and enhance distant metastasis-free survival.
Due to the efficacy of the variety of regimens used to treat uveal melanoma, the authors wanted to understand how treatment outcomes can be maximized and side effects, such as radiation toxicity, can be minimized. To do so, the team identified 199 patients who had uveal melanoma between the years 1988 and 2010 and analyzed the prescribed course of treatment for associated benefits. Overall, five-year distant metastases rate was 10% and five-year overall survival rate was 84%.
Looking at patients stratified into radiation dose, there was no difference in beneficial outcomes following treatment. However, dose had a significant impact on side effects, with a greater dose associated with greater visual acuity loss, worse final visual acuity, and radiation complications. This was true when radiation was applied either to the apex of the tumor or to a depth of five millimeters.
As a result, the authors stated, “Doses at least as low as 69 Gy prescribed to tumor apex achieved [beneficial outcomes] that are similar to radiation doses of 85 Gy to the tumor apex, but with improved visual outcomes.” This suggests a lower radiation burden can be applied without sacrificing cancer fighting ability.
The radiation used in the studies analyzed by the authors is known as Iodine-125. It has been used consistently to treat ocular melanoma, including patients enrolled in the Collaborative Ocular Melanoma Study from the National Eye Institute. It can be a more preferable option for patients to undergo radiation brachytherapy rather than enucleation, as enucleation involves loss of the afflicted eye. A previous study showed no difference in survival when radiation brachytherapy or enucleation was used for treatment.
Combined, this information suggests Iodine-125 brachtherapy with a dose of 69 Gy may be an optimal treatment option for patients with uveal melanoma.