Purpose: To study time trends in the incidence of conjunctival melanoma in Sweden.
Methods: All patients with conjunctival melanoma 1960 to 2005 in Sweden were identified through the Swedish Cancer Registry, cross-checked against hospital files and validated by histopathologic review (97.5%) or detailed hospital records (2.5%). The crude and age-standardized incidences were estimated separately for each gender and the annual change in incidence over time was estimated using a regression model with logarithmic incidence numbers. Time trends of the largest diameter, thickness and location of the tumor when diagnosed were analyzed.
Results: The age-standardized incidence of conjunctival melanoma increased significantly in males (n = 89) from 0.10 cases/million to 0.74 cases/million (P = 0.001) and in females (n = 81) from 0.06 cases/million to 0.45 cases/million (P = 0.007). The annual relative change in age-standardized incidence was 16.9 % (95 % CI, 12.2 % - 21.6 %) in males and 19.5 % (95% CI, 9.3 % - 29.7 %) in females. The age-specific incidence was higher in men and women 65 years and older (1.48 and 1.39 cases/million, respectively) than in younger men and women (0.3 and 0.2 cases/million, respectively). During the period of study, tumors became smaller (P = 0.005) and thinner (P = 0.002) at the time of diagnosis and increasingly arose from parts of the conjunctiva exposed to ultraviolet radiation (P = 0.001).
Conclusions: The incidence of conjunctival melanoma increased in Sweden during the period 1960 through 2005.