Head and Neck Cancer

PV QA 2 - Poster Viewing Q&A 2

MO_26_2611 - Dosimetric Comparison of COMS and Circular Eye Physics Plaques to Treat Uveal Melanoma

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Dosimetric Comparison of COMS and Circular Eye Physics Plaques to Treat Uveal Melanoma
M. Dean1, M. Studenski1, M. Paez-Escamilla2, S. Walter2, A. M. Markoe1, J. W. Harbour2, and S. Samuels1; 1Department of Radiation Oncology, University of Miami Sylvester Comprehensive Cancer Center, Miami, FL, 2Department of Ophthalmology, University of Miami Bascom Palmer Eye Institute, Miami, FL

Purpose/Objective(s): Plaque brachytherapy is an effective treatment for medium-sized uveal melanomas. Multiple types of plaques are available to perform this procedure, and the most commonly used are the COMS (Collaborative Ocular Melanoma Study) plaques. EP (Eye Physics) plaques were developed with the goal of improving dose coverage of the tumor and reducing dose to surrounding normal structures. Since no formal comparison of the COMS and circular EP plaques has been reported, we dosimetrically compared them by examining both tumor coverage and critical structure doses.

Materials/Methods: The charts of patients with uveal melanoma treated with eye plaque brachytherapy at a single institution in 2016 and 2017 were reviewed. The size and location of the tumor relative to the fovea and optic disc were recorded. Both a COMS plan and an EP plan using circular shaped plaques (EP1821, EP2029N, EP2031, EP2340N, EP2342) were generated for each patient. The plans were optimized such that at least 90% of the tumor base + 2 mm margin was covered by 85 Gray (Gy). Dose statistics for the macula, optic disc, and fovea were recorded. We compared the means of each recorded structure with t-Tests to determine if there were any overall dosimetric differences between the two plaques.

Results: A total of 71 patients were used in the data analysis. The mean tumor volume was 0.41 mm3 (range 0.02-2.02 mm3). The mean distance to the fovea was 5.65 mm (range 0-20 mm), and the mean distance to the optic disc was 6.05 mm (range 0-20 mm). 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 macula (p = 0.37; mean difference (MD) = -1.32 Gy ± 12.4; 95% CI: 1.61 to -4.26), optic disc (p = 0.59; MD = 0.46 Gy ± 7.17; 95% CI: 2.15 to -1.24), or fovea (p = 0.92; MD = -0.17 Gy ± 13.8; 95% CI: 3.41 to -3.76) between the COMS and circular EP plaques.

Conclusion: Overall, neither the COMS plaques nor the circular EP plaques provided consistently superior dosimetry for the treatment of uveal melanoma.

Author Disclosure: M. Dean: None. M. Studenski: None. M. Paez-Escamilla: None. S. Walter: None. J. Harbour: None.

Mary Dean, MD

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