Dosimetric comparison of circular Eye Physics and Collaborative Ocular Melanoma Study plaques to treat uveal melanoma

We sought to formally compare Collaborative Ocular Melanoma Study (COMS) and similar-shaped (circular) eye physics (EP) plaques dosimetrically by examining both tumor coverage and critical structure doses.

The plans of patients with uveal melanoma treated consecutively with eye plaque brachytherapy at a single institution from January 2016 to December 2017 were reviewed. Both a COMS plan and an EP plan using plaques of the same shape were generated for each patient using the Isoaid Plaque Simulator software such that >90% of the tumor + 2 mm margin received 85 Gy over 72 hours from iodine-125 sources. Dose statistics were recorded and analyzed using standard statistical methods.

Plans from a total of 62 patients were analyzed. The mean tumor volume was 0.46 cm³ (range: 0.02-2.02), and tumors were located on average 5.89 mm (range: 0-15.0) from the macula and 6.25 mm (range: 0-16.0) from the optic disc. All plans met the treatment planning criteria for tumor coverage and were optimized to reduce dose to the adjacent organs at risk. There were no significant differences in the mean doses to the fovea (mean difference [MD] = -0.87 Gy; 95% confidence interval [CI]: -4.90 to 3.16; p = 0.80), macula (MD = -1.02 Gy; 95% CI: -4.15 to 2.11; p = 0.65), or optic disc (MD = 1.07 Gy; 95% CI: -0.77 to 2.91; p = 0.34) between the COMS and circular EP plaques.

Overall, neither the COMS plaques nor the circular EP plaques provided consistently superior dosimetry for the treatment of uveal melanoma. The choice of plaque may be based on other considerations such as cost and surgeon preference.