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 ⩾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.
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Funding Supported by grants from Karin Sandqvist’s Foundation for the Visually Impaired, St Eriks Eye Research Foundation and the Swedish Research Council.
Competing interests None declared.
Provenance and Peer review Not commissioned; externally peer reviewed.
Ethics approval The research protocol for the present study was approved by the Human Ethics Committee at the Karolinska Institute, in accordance with the statutes of the World Medical Association’s Declaration of Helsinki.