Sociodemographic and clinical predictors of participation in two randomized trials: findings from the Collaborative Ocular Melanoma Study COMS report no. 7.

Collecting sociodemographic and clinical data concerning patients who choose not to enroll in a randomized clinical trial can be useful in assessing the feasibility of attaining sample size goals during the course of a trial. It can also aid in addressing the extent of generalizability of trial findings after a trial has ended. The Collaborative Ocular Melanoma Study (COMS) consists of two multicenter randomized clinical trials to evaluate the effectiveness of radiotherapy in comparison to standard enucleation (removal of the affected eye) in prolonging survival of patients with choroidal melanoma. One trial is for patients with large tumors and the other trial is for patients with medium-sized tumors. The same baseline sociodemographic and clinical data were collected for both enrolled patients and eligible patients who did not enroll in the randomized trials during the first 3 years of patient recruitment. Partial information on nonrandomized patients was collected thereafter. Recruitment ended in the large tumor and medium tumor trials on December 31, 1994, and July 31, 1998, respectively. From November 1986 through July 1998, 6906 patients with choroidal melanoma were evaluated for the randomized trials, of whom 4191 (61%) were eligible for enrollment. Logistic regression methods were used to identify factors predictive of trial participation. Sociodemographic factors that appeared to be associated (p < 0.15) with participation in the univariable models in the medium tumor trial were age 60 years or older, less than college education, nonmanagerial occupation, current smoking, and residing in the same state as a COMS clinical center. In the large tumor trial, males, individuals who were not college-educated, and individuals residing in the same state as a COMS clinical center were more likely to enroll. In both trials, clinical determinants of participation were larger tumor dimensions and initial visual acuity worse than 20/20 in the study eye. In multivariable regression models, the variables that were significantly predictive of enrollment (p < 0.05) in at least one of the trials were older age, residence in the same state, larger tumor basal diameter, and worse initial visual acuity in the study eye. Knowledge of possible sociodemographic and clinical predictors of differentials in patient participation for nonenrolled patients may help to refine patient education and recruitment strategies for future trials. Patient enrollment in clinical trials may be increased by heightened physician awareness of such predictors, strategies for addressing these differences, and enhanced communication between physicians and patients.