University of Minnesota Radiation Oncology Clinic University Campus Minneapolis, MN
S. Mishra1, A. Gao2, L. Kollitz2, G. Sodhi3, P. Tang4, Y. Watanabe1, A. Venteicher5, D. Koozekanani6, C. Ferreira1, E. Domingo-Musibay7, J. Yuan8, M. A. Reynolds1, and K. E. Dusenbery1; 1University of Minnesota: Department of Radiation Oncology, Minneapolis, MN, 2University of Minnesota, Minneapolis, MN, 3Retina Consultants of Minnesota, Minneapolis, MN, 4Storm Eye Institute, Charleston, SC, 5University of Minnesota: Department of Neurosurgery, Minneapolis, MN, 6University of Minnesota: Department of Ophthalmology and Visual Neurosciences, Minneapolis, MN, 7Allina Health, Minneapolis, MN, 8Department of Radiation Oncology, University of Minnesota Medical School, Minneapolis, MN
Purpose/Objective(s): Uveal melanoma (UM), the leading primary intraocular malignancy in adults, often falls outside the treatable scope of plaque brachytherapy for large or juxta-papillary tumors. This study evaluates a dose-reduced non-invasive Stereotactic Radiosurgery (SRS) protocol amidst varied SRS practices and doses (18-45 Gy) and aims to standardize treatment and assess its effectiveness and safety for comparable local control to plaque brachytherapy. Materials/
Methods: In this IRB-approved, retrospective non-comparative case series, we evaluated clinical and radiosurgical data from 17 UM patients treated with GK SRS and surgical fixation of extraocular muscles from 2020 to 2023. Treatment parameters included tumor volume, peripheral dose, tumor coverage, gradient index, and maximum doses to the lens and optic nerve. Treatment efficacy was assessed through changes in primary UM apical height pre- and post-SRS to quantify local control. Safety outcomes include visual acuity, cataract progression, and the incidence of radiation retinopathy, glaucoma, neovascularization, and enucleation. Results: 17 UM patients (65% male, 59% left-sided) underwent GK SRS. Mean tumor volume was 0.964 cm³ (± 0.446 cm³), with 35.3% large and 64.7% medium in size, per COMS classification. A median peripheral dose of 24 Gy (range: 24-25 Gy) was administered, achieving 98.9% (± 1%) tumor coverage with gradient index 2.89 (± 0.19). At mean follow-up of 27.8 months (± 6.9 months), we noted a 24.9% decrease in tumor apical height at 1 year (p = 0.00015) and a 30.5% decrease at the last follow-up (p = 0.00013), compared to baseline, with an overall 94.4% local control. Visual acuity was stable or improved in 64.7% of patients at 1 year, with 52.9% having >20/200 vision at last follow-up. 53% experienced radiation retinopathy and 42.9% of patients without prior cataract surgery had cataract progression. Glaucoma developed in 23.5% of patients, with no cases in the first year. 35.3% had neovascularization, of whom half required enucleation. Conclusion: Our study confirms GK SRS as an effective alternative to enucleation for UM patients unsuitable for brachytherapy or for those desiring to avoid surgery. Despite treating medium and large UM with a relatively low peripheral dose of 24 Gy, local control was high and comparable to COMS report 19, with most patients avoiding legal blindness. However, patients still had high risk of cataract progression, radiation retinopathy, and glaucoma, with neovascularization often preceding enucleation. Based on our results, we propose a 24 Gy GKSRS protocol as a viable treatment option for UM, striking a balance between effective tumor control and visual function preservation.
