Incidence of malignant melanoma of the skin in the five nordic countries: significance of solar radiation

Abstract

The incidence of malignant melanoma of the skin has increased rapidly among white people during the last decades. Excellent possibilities for detailed epidemiological analysis of malignant melanoma are provided in the Nordic countries (Denmark, Finland, Iceland, Norway, Sweden), where the five national cancer registries were established during the period 1942–1958. Their materials are based on reports from hospitals and histopathological laboratories and death certificates. The organization of the registries is largely similar, and efforts have been made to bring the materials into conformity. More than 14,000 cases are included in the analysis, which covers the period 1953–1972 in Denmark, Finland and Norway, 1955–1974 in Iceland and 1959–1971 in Sweden. The tumors have been grouped by anatomical site as follows: face, neck/trunk, upper limb, lower limb, and other and unspecified sites. The incidence of malignant melanoma is similar in Denmark, Norway and Sweden. Lower incidence rates are observed in Finland and Iceland. Time trends in incidence are remarkable and clearly statistically significant, except for Iceland where the number of cases was very small. The period for doubling the incidence rate ranged from 10 to 17 years. Striking contrasts by sex are observed when the material is grouped according to primary site. There is a male preponderance for incidence on the neck/trunk and the reverse is found for the lower limbs. There is only a slight increase in incidence of malignant melanoma of the face, whereas for the neck/trunk, particularly among males, and for the lower limbs, particularly among females, there is a consistent upward trend. A difference between the face, on the one hand, and the neck/trunk and lower limbs on the other, is also disclosed in the curves showing the age‐specific incidence rates.In conclusion, the results indicate that there is a marked real increase in incidence of malignant melanoma of the skin in all the Nordic countries. This increase is in accordance with the hypothesis of the association between solar radiation and risk of cutaneous melanoma, and could possibly be ascribed to changes in habits of leisure and clothing. It ought to be possible to introduce control measures against malignant melanoma which is becoming a serious cancer problem. This is a challenge for future preventive medicine.