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Jonathan Lu, Ellen Redenbo, Susanna S Park; Ultrasonography versus Transillumination to Localize Choroidal Melanomas in Preparation for Proton Beam Irradiation. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5342.
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© ARVO (1962-2015); The Authors (2016-present)
Proton beam therapy is a highly effective, globe saving local treatment for ocular melanoma, but efficacy of treatment is dependent on proper localization and placement of tantalum rings in preparation for irradiation. The ring placement currently relies on tumor localization intraoperatively using transillumination of the globe. The goal of this study was to evaluate the relative accuracy of this localization method compared to ultrasonography, and to identify tumor characteristics that would affect the relative accuracy of these two methods.
This study is a retrospective chart review of all eyes with ocular melanoma from 2006 to 2014 who had tantalum rings placed in preparation for proton beam therapy where the placement of the rings were localized using both transillumination and ultrasonography. All tantalum rings were placed under general anesthesia by the same surgeon. Each eye had four rings placed at the edges of the tumor. Transillumination through the globe was performed intraoperatively to determine the distance between the rings to tumor edge. The distance between the ring and tumor edge was reconfirmed by ultrasonography postoperatively among the identified patients.
Among 53 patients with ocular melanoma treated with proton beam irradiation, we identified 18 patients (18 eyes) who had tumor localization performed using both ultrasonography and transillumination. The mean age was 63 years (range 22 to 89 years) and 44% were female. Among 71 rings placed around 18 tumors, 30 rings (42%) had tumor to ring distance of 1mm or greater difference between the two methods (range 0 to 4 mm difference, mean 1.1 mm + 0.3 mm). The tumor feature associated with a greater difference in tumor localization between the two imaging techniques was increasing tumor height (p value = 0.04). Tumor pigmentation (p value = 0.77) and tumor location (p value = 0.16) did not significantly affect the difference in tumor localization using the two imaging methods in this study.
Tumor localization with tantalum rings in preparation for proton irradiation for treatment of choroidal melanoma may have some limitation in accuracy when using transillumination method alone. Postoperative ultrasonography may be a useful supplemental method of reconfirming the accuracy of tumor localization especially in tumors of increasing thickness.
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