Objective: To compare pre-enucleation clinical and echographic measurements with postenucleation histopathological measurements of choroidal melanoma of a size and in a location suitable for iodine 125 brachytherapy. Design: Cross-sectional study of patients with melanoma classified as medium-sized who were assigned to the enucleation arm of the randomized trial of 121I brachytherapy vs enucleation conducted by the Collaborative Ocular Melanoma Study (COMS) Group. Methods: Measurements of melanoma dimensions by clinical, echographic, and histopathological examinations were compared for 644 eyes. Outcomes: Tumor longest basal diameter and apical height. Results: Tumor dimensions were available for 644 (98%) of 660 patients who had unilateral medium-sized choroidal melanoma and were randomly assigned to enucleation. The clinical and histopathological measurements of the longest basal diameter agreed within ±2 mm for 371 eyes (58%). The clinical measurement was less than the histopathological measurement by more than 2 mm in 32 eyes (5%), which occurred more frequently when the tumor was within 2 mm of the optic disc. The echographic and histopathological measurements of apical height agreed within ±2 mm in 579 eyes (90%); the echographic measurement was less than the histopathological measurement in only 2 cases. Features associated with echographic estimates larger than histopathological measurements were greater tumor height and anterior tumor apex location. Conclusions: Our results suggest that tumor measurements made according to COMS protocol were highly reliable in planning radioactive plaque therapy and monitoring changes in tumor size after such treatment.
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