Outcomes of choroidal melanomas treated with eye physics plaques: A 25-year review

Abstract

Purpose: To review long-term outcomes of the University of Southern California Plaque Simulator (PS) software and Eye Physics (EP) plaques. We hypothesize that the PS/EP system delivers lower doses to critical ocular structures, resulting in lower rates of radiation toxicity and favorable visual outcomes compared to Collaborative Ocular Melanoma Study plaques, while maintaining adequate local tumor control.

Methods and materials: Retrospective review of 133 patients treated for choroidal melanoma with ¹²⁵I brachytherapy, using PS software and EP plaques, from 1990 through 2015. A dose of 85 Gy at a rate of 0.6 Gy/h was prescribed to the tumor apex (with a typical margin of 2 mm) over 7 days. Primary outcomes were local tumor recurrence, globe salvage, and metastasis. Secondary outcomes were changes in visual acuity and radiation complications.

Results: With median followup of 42 months, 5-year Kaplan-Meier estimated rates for tumor control, globe salvage, and metastatic-free survival were 98.3%, 96.4%, and 88.2%, respectively. Median doses to the macula and optic nerve were 39.9 Gy and 30.0 Gy, respectively. Forty-three percent of patients developed radiation retinopathy, and 20% developed optic neuropathy; 39% lost ≥6 Snellen lines of vision.

Conclusions: The PS/EP system is designed to improve the accuracy and conformality of the radiation dose, creating a steep dose gradient outside the melanoma to decrease radiation to surrounding ocular structures. We report favorable rates of local tumor control, globe salvage, metastases, and radiation complications when compared to the Collaborative Ocular Melanoma Study and other studies. Overall, the PS/EP system results in excellent tumor control and appears to optimize long-term visual and radiation-related outcomes after brachytherapy.

Keywords: Brachytherapy; Choroidal melanoma; Eye physics; Plaque simulator; Radiation retinopathy; Uveal melanoma.

Fig. 1.

Kaplan–Meier curves demonstrating postbrachytherapy (a) local tumor control rate of 98.29% (95% CI, 95.94–100%) at 5 years and (b) globe salvage rate of 96.41% (95% CI, 92.94–99.88%) at 5 years.

Fig. 2.

Ven diagram demonstrating (a) overlap between patients who received >40Gy to the fovea and >55Gy to the disc. (b) Of patients with dose >40Gy to the fovea, the overlap of those who developed radiation retinopathy and lost >6 lines of vision. (c) Of patients with dose >55Gy to the optic disc, the overlap of those that developed radiation optic neuropathy and lost >6 lines of vision.

Fig. 3.

Percentage of patients with radiation optic neuropathy with tumors within 1, 1–2, 2–3, and 3 + disc diameters (DDs) of the optic nerve. There was a significant correlation between tumors located closer to the optic nerve and the development of optic neuropathy (p = 0.0049).

Fig. 4.

(a) Sample retina dose–area histogram from Plaque Simulator (PS) demonstrating sharp drop-off of relative doses to the macula and optic disc. In this case, <45% of the macular area and <10% of the optic disc area received >45 Gy. (b) Sample diagram from PS showing tumor fundus photography overlaid with dose distributions.