Malignant melanomas on head/neck and foot: differences in time and latitudinal trends in Norway

Abstract

Cutaneous malignant melanoma (CMM) incidence continues to increase in many parts of the world. Solar ultraviolet (UV) radiation is the main environmental risk factor for CMM. Different body locations are subjected to different doses and exposure patterns of solar UV. Time and latitudinal trends of CMMs on shielded and exposed skin give valuable information about the aetiology of these cancers. In this study, we have compared the time and latitudinal trends of CMM incidence on skin areas which are chronically (head and neck) and rarely (foot) exposed to UV radiation, to gain more information about the relationship between sun doses, exposure patterns and melanomagenesis. We have analysed epidemiological data from the Cancer Registry of Norway, for foot and head and neck CMM for two time periods: 1966-1986 and 1987-2007. Cutaneous malignant melanoma incidence rate on head and neck has increased with time, while incidence rates of foot CMM have remained almost constant with time in Norway. There is a large north-south gradient in incidence rates of CMM on head and neck in Norway, while there is almost no north-south gradient for CMM incidence on foot. Comparisons of time trends and latitudinal trends of the incidence rates of CMM on head/neck and on foot indicate that solar radiation plays a role in the induction of the former CMM but probably not for the latter.