Are Cutaneous Melanomas of Specified Thickness Showing Deeper Levels of Invasion at Diagnosis?

Secular trends in Clark level were investigated by Breslow category for 8,432 invasive cutaneous melanomas ‍diagnosed in South Australia in 1980-2000. More recently diagnosed lesions were found to have deeper levels. After ‍adjusting for age at diagnosis, tumour site, histology, and thickness measured in half millimetres, the relative odds ‍(95% confidence limits) of penetration to the reticular dermis or subcutaneous fat were 1.99 (1.59, 2.50) for the 1987- ‍93 diagnostic period, and 2.82 (2.25, 3.54) for 1994-2000, when compared with 1980-86. After adjusting for melanoma ‍thickness, the secular trends for deeper lesions applied to a broad cross-section of socio-demographic sub-groups, ‍tumour sites, and histological types. While this similarity in trend would be consistent with a measurement effect, a ‍real change cannot be ruled out and increased emphasis on earlier detection may be warranted. The prognostic ‍implications of changes in inter-relationships between measures of thickness and level require periodic re-evaluation. ‍