Factors predictive of growth and treatment of small choroidal melanoma: COMS Report No. 5. The Collaborative Ocular Melanoma Study Group.

OBJECTIVES: To describe time to tumor growth of a prospectively followed group of patients with small choroidal melanoma and to determine baseline clinical and photographic characteristics associated with time to growth.

METHODS: The Collaborative Ocular Melanoma Study (COMS) is a set of clinical trials designed to compare radiotherapy and enucleation in the treatment of medium- and large-size choroidal melanoma. From December 1986 to August 1989, patients with small choroidal melanoma, not large enough to be eligible for the COMS clinical trials, were offered participation in a nonrandomized prospective follow-up study. Small choroidal melanomas were defined as 1.0 to 3.0 mm in apical height and 5.0 to 16.0 mm in largest basal dimension. A total of 204 patients were enrolled in the study and were followed up annually through August 1989. An assessment of current size of tumor, treatment status, and vital status was conducted in 1993-1994; an additional assessment of treatment and vital status was performed in 1995-1996.

RESULTS: Of 188 small tumors not treated at the time of study enrollment, 46 grew during follow-up to a size that was large enough to be eligible for the COMS clinical trials. The Kaplan-Meier estimates of proportion of tumors that grew were 21% (95% confidence interval, 14%-27%) by 2 years and 31% (95% confidence interval, 23%-39%) by 5 years. Factors significantly associated with time to growth in a Cox proportional hazards regression model were greater initial tumor thickness and diameter, presence of orange pigment, absence of drusen, and absence of areas of retinal pigment epithelial changes adjacent to the tumor.

CONCLUSIONS: Of small choroidal melanomas initially managed by observation, 21% demonstrated growth by 2 years and 31% by 5 years. The clinical and photographic features of these tumors confirm previous findings and are useful in identifying patients with small tumors at highest risk of short-term growth.