Time trends in tumour thickness vary in subgroups: analysis of 6475 patients by age, tumour site and melanoma subtype.

An elevated tumour thickness is strongly associated with an increased risk of mortality in melanoma patients. In the last few decades, an overall decrease of the tumour thickness to prognostically more favourable levels has been observed in several countries. Nevertheless, it is not clear whether this positive time trend occurred uniformly in specific subgroups of melanoma patients. Therefore, we aimed to assess time trends of tumour thickness by age group, tumour site and melanoma subtype. The study population consisted of 6475 patients with histologically proven primary invasive cutaneous melanomas seen at the Department of Dermatology and Allergology at the Ludwig-Maximilian-University Munich between 1977 and 2000. Age-adjusted time trends were assessed using linear and logistic regression analysis. Overall, a positive time trend with a decreasing tumour thickness was observed during the observation period in most subgroups. However, no significant time trend was observed in patients with a melanoma on the feet or with a nodular or acrolentiginous melanoma. The almost constant high tumour thickness of these patients might be caused by underaddressing the specific traits of these melanomas in earlier prevention campaigns. An important goal for the upcoming years should consist of a positive time trend with a decreasing tumour thickness in these subgroups.