Epidemiologic study of time and space clustering of 4 cases of choroidal malignant melanoma

J. P. Ganley and K. Fontenot
Department of Ophthalmology, Louisiana State University Medical Center-Shreveport, USA.

OBJECTIVE: To identify common risk factors that might be associated with a cluster of 4 cases of choroidal malignant melanoma that occurred in a manufacturing plant between 1982 and 1985. DESIGN: Survey of choroidal malignant melanoma cases in Caddo and Bossier parishes during the same time frame. METHODS: We identified 4 additional individuals with choroidal malignant melanoma first diagnosed during the study period. Characteristics of the workplace were examined and a questionnaire was administered to all subjects to ascertain exposures to putative carcinogens and to putative risk factors for intraocular malignant melanoma. Observed and expected incidence rates were calculated. RESULTS: The overall incidence of intraocular malignant melanoma for the 2 parishes during the 4-year period was 0.56 cases per 100,000 population per year, similar to the expected rates for this population. The incidence rate for the manufacturing plant employees was 16.5 cases per 100,000 per year. The mean age at diagnosis for workers at the plant was 38.7 years compared with 69.2 years for nonplant employees. CONCLUSIONS: The close occurrence of manufacturing plant cases in time and space and the younger age of the people are consistent with a cluster of intraocular melanoma cases. No specific risk factors were found in the workplace environment to impute a causal association.