Sun exposure and risk of melanoma

Ambient UVB and melanoma risk in the United States: a case-control analysis

PURPOSE

Exposure to ultraviolet-B (UVB) radiation is a well-established risk factor for human cutaneous malignant melanoma. Intermittent and cumulative exposures from UVB have been estimated most often by interview questionnaire. This study assessed cumulative UVB using a ground-based measurement instrument to estimate the association between UVB and melanoma.

METHODS

Population-based, incident cases of melanoma (n = 380) and frequency-matched controls (n = 364) residing in Connecticut at diagnosis were interviewed between 1987 and 1989 about recreational and vacation activities, sun-protection practices, occupation, and other factors. Using a residential history, regression estimates of lifetime UVB were derived from ambient measures of UVB, adjusted for intermittent exposure.

RESULTS

Cases and controls received 29% of lifetime mean UVB in the first 15 years of life. Number of days per year in recreational activity during childhood and late adulthood were associated with increased melanoma risk. When estimating lifetime UVB adjusted for intermittent exposure, melanoma risk peaked at a 5.7-fold increased risk in the ninth decile.

CONCLUSION

Sporadic and chronic sun exposure play a role in melanoma etiology. Skin-protection practices should be encouraged across levels of sun intensity, not only in childhood but throughout adulthood.

Mechanism of UV-related carcinogenesis and its contribution to nevi/melanoma

Melanoma consists 4-5 % of all skin cancers, but it contributes to 71-80 % of skin cancers deaths. UV light affects cell and tissue homeostasis due to its damaging effects on DNA integrity and modification of expression of a plethora of genes. DNA repair systems protect cells from UV-induced lesions. Several animal models of melanoma have been developed (Xiphophorus, Opossum Monodelphis domestica, mouse models and human skin engrafts into other animals). This review discusses possible links between UV and genes significantly related to melanoma but does not discuss melanoma genetics. These include oncogenes, tumor suppressor genes, genes related to melanocyte-keratinocyte and melanocyte-matrix interaction, growth factors and their receptors, CRH, ACTH, α-MSH, glucocorticoids, ID1, NF-kappaB and vitamin D3.

Nichthereditäre Photodermatosen im Kindesalter

Non-hereditary photodermatoses with well-known trigger factors and idiopathic light eruptions occur quite frequently during childhood and are at least temporarily associated with a marked impairment of quality of life in affected patients and their parents. Thus, it is crucial that the involved specialties are familiar with acquired UV-associated disorders in order to guarantee a quick diagnosis and effective therapy. Additionally, the recurrence of photodermatoses associated with potentially severe long-term complications has to be prevented. This requires a stringent prophylaxis that can only succeed after age-adapted instruction of the patient and parents.

The geographic distribution of melanoma incidence in Massachusetts, adjusted for covariates

Background

The aims of this study were to determine whether observed geographic variations in melanoma cancer incidence in both gender groups are simply random or are statistically significant, whether statistically significant excesses are temporary or persistent, and whether they can be explained by risk factors such as socioeconomic status (SES) or the percent of the population residing in an urban rather than a rural area. Between 1990 and 1999, 4774 female and 5688 male melanomas were diagnosed in Massachusetts residents. Cases were aggregated to census tracts and analyzed for deviations from random occurrence with respect to both spatial location and time.

Results

Thirteen geographic areas that deviated significantly from randomness were uncovered in the age-adjusted analyses of males: five with higher incidence rates than expected and eight lower than expected. In the age-adjusted analyses of females, six areas with higher incidence rates and eight areas with lower than expected incidence rates were found. After adjustment for SES and percent urban, several of these areas were no longer significantly different.

Conclusion

These analyses identify geographic areas with invasive melanoma incidence higher or lower than expected, the times of their excess, and whether or not their status is affected when the model is adjusted for risk factors. These surveillance findings can be a sound starting point for the shoe-leather epidemiologist.