Incidence trends of melanoma of the skin compared with other localisations, in the Norwegian population, 1956-2005.

BACKGROUND: Increasing incidence rates (IRs) of cutaneous malignant melanoma (CMM) have been associated with increased exposure to ultraviolet radiation (UVR). The aim of this study was to compare the changes over time in IRs of malignant melanoma in anatomical localisations exposed to different levels of UVR in the same population. PATIENTS AND METHODS: All incident cases of melanoma (invasive) diagnosed 1956-2005 were extracted from the database of the Cancer Registry of Norway. The average percentage change of the age-standardised IRs per 5-year period of diagnosis was calculated (loglinear regression) by anatomical localisation (skin, eye, internal organs and external genitalia). RESULTS: CMM represented 91.7% of the total number of melanomas, while ocular melanoma and melanoma in the internal organs represented 6.2% and 1.2%, respectively. The average quinquennal percentage increase in IRs for CMM and melanoma in internal organs was 23.3% [95% confidence interval (CI) 20.9-25.8] and 14.0% (95% CI 8.2-19.7), respectively. The corresponding analysis for ocular melanoma showed an increase of 1.3% (95% CI -1.5 to 4.2) and a decrease (not significant) for melanoma on male (-8.8%) and female (-2.1%) external genitalia. CONCLUSION: A wide variation in IRs and trends between the four anatomical localisations with unlike levels of UVR exposure suggests different causal pathways for melanoma.

Birth weight and melanoma risk: a population-based case-control study.

We investigated whether lower birth weight was associated with lower risk of melanoma later in life. This population-based case-control study included all incident cases of histologically verified invasive melanoma diagnosed until 31 December 2003 in the Norwegian population born between 1967 and 1986 (n=709). The control group without malignant disease was established by random sampling from the same source population as the cases (n=108 209). Data on birth weight, gender, mother's residence and parental age at the time of birth were collected from the Medical Birth Registry of Norway and data on cancer from the Cancer Registry of Norway. The Mantel-Haenszel test of linear trend showed no trend in risk across the birth weight categories: individuals in the highest quartile of birth weight (>or=3860 g) had an odds ratio (OR) of 1.19 (95% confidence interval, CI: 0.77-1.84) compared to individuals with birth weight <2500 g. The adjusted OR was 0.81 (95% CI: 0.52-1.26) for birth weight below 2500 g (exposed). Though not statistically significant, the results suggest that low birth weight might influence the risk of melanoma later in life.