Incidence Of Thin Melanoma Is Increasing Most

Even though thin melanoma is increasing the most, the number of cases of thicker melanoma is also steadily on the rise, shows a major study of melanoma incidence in Norway since the 1980s. The thickness of the tumour is an important factor for the prognosis at the time of diagnosis.

Norway ranks third in the world when it comes to the incidence of melanoma (formerly called mole cancer) and we have the highest mortality from this disease in Europe.

With the help of national data from the Cancer Registry of Norway, post-doctoral fellow Raju Rimal and professor Marit B. Veierød have studied the evolution of melanoma incidence during the period 1983-2019. They collaborated on this research at the Department of Biostatistics at the Institute of Basic Medical Sciences.

Important to investigate melanoma trends

- In order to understand the incidence of this disease and to prevent melanoma, it is important to investigate trends in incidence, says Veierød.

- We found a substantial increase in the incidence of thin melanoma measuring under one millimetre, and an increase in the incidence of thicker melanoma. The rate of incidence of thicker melanoma is higher among men than women and this difference between the genders increases with age, explains Rimal.

- The results of this study show that there is clearly a need for more awareness about skin changes that grow rapidly, especially in older adults and men, emphasises Veierød.

The incidence curve flattens out in an inexplicable way

During the period of years studied, over 45,000 patients were diagnosed with melanoma in Norway. The incidence of thin melanoma increased substantially from 1983 to 1990. This was followed by a period when there was no increase, before there was again a sharp increase from 2004.

- We have not yet found an explication for this 15-year flattening out period and we found no such flat period in the incidence of thicker melanoma.