Scleral Necrosis after Plaque Radiotherapy of Uveal Melanoma: A Case-Control Study

Abstract

To identify risk factors and outcome of scleral necrosis after plaque radiotherapy of uveal melanoma. Case-control study. A total of 73 cases with scleral necrosis and 73 controls without necrosis after plaque radiotherapy. Controls were matched for anteroposterior tumor epicenter and follow-up duration. Plaque radiotherapy with iodine-125, cobalt-60, iridium-192, or ruthenium-106. Scleral necrosis. Of 5057 patients treated with plaque radiotherapy for uveal melanoma, 73 (1%) developed radiotherapy-induced scleral necrosis. Scleral necrosis occurred in <1% of patients (3/1140) when plaque radiotherapy was used for tumors <3 mm in thickness, 1% of patients (33/3155) with 3- to 8-mm tumor thickness, and 5% of patients (37/762) with >8-mm-thick tumors. On the basis of tumor location, scleral necrosis was detected after plaque radiotherapy of iris melanoma in 0% of patients (0/91), ciliary body melanoma in 29% of patients (67/235), and choroid melanoma in <1% of patients (6/4731). The mean time interval between plaque radiotherapy and scleral necrosis was 32 months (median, 23 months; range, 4-126 months). The mean basal dimension of scleral necrosis was 4 mm (median, 3 mm; range, 1-15 mm), equivalent to 29% of mean tumor base (median, 24%; range, 6%-100%) and 22% of mean plaque size (median, 19%; range, 5%-75%). Multivariate analysis of factors that predicted clinically evident scleral necrosis included ciliary body (P = 0.0001) and pars plana to ora serrata (P < 0.0001) locations of anterior tumor margin, tumor thickness ≥ 6 mm (P = 0.0001), and radiation dose ≥ 400 Gy to the outer sclera (P = 0.0455). Scleral necrosis remained stable in 48% of patients (35/73), increased in size/severity in 48% of patients (35/73), or progressed to scleral perforation in 4% of patients (3/73) over a mean follow-up of 79 months (median, 54 months; range, 5-351 months). Treatment of scleral necrosis included observation in 81% of patients (59/73), scleral patch graft in 14% of patients (10/73), and enucleation in 5% of patients (4/73). Scleral necrosis after plaque radiotherapy of uveal melanoma was detected in 1% of cases. Factors predictive of scleral necrosis included increasing tumor thickness, ciliary body and peripheral choroidal location, and higher radiation dose to sclera. Most patients (81%) did not require treatment, and 4% evolved to full-thickness perforation. The author(s) have no proprietary or commercial interest in any materials discussed in this article.