Time trends in the incidence of conjunctival melanoma in Sweden

Abstract

Aim: To study time trends in the incidence of conjunctival melanoma in Sweden.

Methods: All patients with conjunctival melanoma from 1960 to 2005 in Sweden were identified through the Swedish Cancer Registry, cross-checked against hospital files, and validated by histopathological review (97.5%) or detailed hospital records (2.5%). The crude and age-standardised incidences were estimated separately for each sex and the annual change in incidence over time was estimated using a regression model with logarithmic incidence numbers. Time trends for the largest diameter, thickness and location of the tumour when diagnosed were analysed.

Results: The age-standardised incidence of conjunctival melanoma increased significantly in men (n = 89) from 0.10 cases/million to 0.74 cases/million (p = 0.001) and in women (n = 81) from 0.06 cases/million to 0.45 cases/million (p = 0.007). The annual relative change in age-standardised incidence was 16.9% (95% confidence interval (CI) 12.2 to 21.6) in men and 19.5% (95% CI 9.3 to 29.7) in women. The age-specific incidence was higher in men and women > or = 65 years (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, tumours 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).

Conclusion: The incidence of conjunctival melanoma increased in Sweden during the period 1960 to 2005.