Objectives: To describe characteristics of patients evaluated for the Collaborative Ocular Melanoma Study (COMS) randomized clinical trial of iodine 125 brachytherapy for choroidal melanoma by enrollment status, and to compare characteristics of patients enrolled with those of patients with tumors of eligible size who did not enroll in order to assess the extent to which findings from the clinical trial can be generalized to future patients. Methods: For all patients diagnosed with choroidal melanoma and evaluated for the clinical trial at COMS centers from November 1986 through July 31, 1998, selected data were transmitted to the COMS Coordinating Center, Baltimore, Md, where they were integrated and analyzed. Data included ophthalmic and medical history, examination findings, and visual acuity measurements recorded prior to enrollment; standardized A- and B-scan echographic examination findings; and wide-angle fundus photographs and fluorescein angiograms. Results: Of 8712 patients with choroidal melanoma, 5046 had tumors of eligible size; of these, 2882 (57%) were eligible for enrollment, and 1317 (46% of eligible patients, 26% of patients with tumors of eligible size) enrolled. Most differences between eligible and ineligible patients corresponded to eligibility and exclusion criteria. However, ineligible patients were older and had thicker tumors than eligible patients. Eligible patients who enrolled were slightly older and had larger tumors than those who did not enroll. Nearly half (48%) of enrolled patients had choroidal melanoma with the apex located temporal to the fovea, compared with 40% of eligible patients not enrolled and 29% of ineligible patients. Conclusions: This trial was designed to yield internally valid treatment comparisons through random assignment to treatment at time of enrollment. Information from this and other studies document that enrolled patients were similar to other patients with choroidal melanoma who were treated with 125I brachytherapy. These findings support the external validity of the trial and applicability of treatment findings to all patients who meet the criteria used to judge eligibility for the trial.
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