Relationship between sun exposure and melanoma risk for tumours in different body sites in a large case-control study in a temperate climate
Introduction
Many case-control studies have established phenotypic and behavioural risk factors for melanoma in populations of European origin, summarised in meta-analyses.1, 2, 3 A pooled analysis by our group4 of 15 studies confirmed that recreational sun exposure and sunburn are strong predictors of melanoma at all latitudes, whereas measures of occupational and total sun exposure appear to predict melanoma on usually-exposed body sites only at low latitudes.4 Thus in Europe and much of North America the dominant pattern of sun exposure associated with risk in fair-skinned individuals was shown to be recreational.
The relationship between sun exposure and risk is however thought to be complex: for example some studies have suggested that occupational sun exposure might actually be protective for melanoma.2 Hypotheses developed to explain this apparent anomaly are that continuous sun exposure (not associated with severe sunburn) might be protective for melanoma either by inducing photoadaptation (increased melanisation and epidermal thickening)5 or as a result of the induction of higher levels of vitamin D. Intense sun exposure leads to both DNA damage and immunosuppression,6 which are together thought to mediate carcinogenesis, and photoadaptation is thought to reduce the DNA damage.5 There are limited data to support a role for vitamin D in melanoma prevention, although some have hypothesised such a role.7 There was no evidence in a recently published cohort study of a protective effect of reported greater vitamin D intake on melanoma risk8 for example, but there are genetic data to suggest that inherited variation in the vitamin D receptor (VDR) gene is associated with melanoma risk, recently published in meta-analyses.9
We have carried out a large case-control study using a very detailed sun exposure questionnaire10 in order to better understand the complexities of the relationship between sun exposure and melanoma risk.
Section snippets
Materials and methods
Studies were approved by the UK Multi-Centre Research Ethics Committee (MREC) and the Patient Information Advisory Group (PIAG). Population-ascertained incident melanoma cases were recruited to a case-control study in a geographically defined area of the UK (Yorkshire and the Northern Region south of the River Tyne) (67% participation rate); 960 cases (aged 18–76 years) were diagnosed in the period from September 2000 to December 2005, as described previously.9, 11 Recruitment (and therefore
Results
The recruited patients were broadly representative of the total eligible population of melanoma cases (Table 1), with a similar sex ratio.15 The differences predominantly reflect the study of upper age limit of 76 years resulting in proportionately fewer head and neck tumours.
Cases and population controls were of similar age and sex with a small excess of young cases (under 40 years) and older controls. Cases were marginally more deprived than the controls (two sample t-test, p = 0.01), as reported
Discussion
The lack of a simple cumulative relationship between melanoma risk and sun exposure has caused difficulties in interpreting and conveying the nature of risk to the public. This has further recently been compounded by concerns that low levels of vitamin D, which might result from sun avoidance designed to reduce melanoma risk, could have negative effects on health generally.17, 18
We therefore carried out a case-control study addressed to better understanding the relationship between sun exposure
Conflict of interest statement
None declared.
Acknowledgements
The collection of samples in the Melanoma Cohort Study was funded by Cancer Research UK (Project Grant C8216/A6129 and Programme awards C588/A4994 and C588/A10589) and by the NIH (R01 CA83115). Recruitment was facilitated by the UK National Cancer Research Network. Julian H. Barth and Helen P. Field from the Department of Clinical Biochemistry at Leeds Teaching Hospitals Trust carried out the measurement of serum vitamin D. Patricia Mack and Kate Gamble collected data for the studies. Paul King
References (25)
- et al.
Meta-analysis of risk factors for cutaneous melanoma: I. Common and atypical naevi
Eur J Cancer
(2005) - et al.
Meta-analysis of risk factors for cutaneous melanoma: II. Sun exposure
Eur J Cancer
(2005) - et al.
Meta-analysis of risk factors for cutaneous melanoma: III. Family history, actinic damage and phenotypic factors
Eur J Cancer
(2005) - et al.
Increased UVA exposures and decreased cutaneous vitamin D(3) levels may be responsible for the increasing incidence of melanoma
Med Hypotheses
(2009) - et al.
A cohort study of vitamin D intake and melanoma risk
J Invest Dermatol
(2009) - et al.
Vitamin D receptor gene polymorphisms, serum 25-hydroxyvitamin D levels, and melanoma: UK case-control comparisons and a meta-analysis of published VDR data
Eur J Cancer
(2009) - et al.
Site-specific protective effect of broad-spectrum sunscreen on nevus development among white schoolchildren in a randomized trial
J Am Acad Dermatol
(2005) - et al.
Exposure to the sun and sunbeds and the risk of cutaneous melanoma in the UK: a case-control study
Eur J Cancer
(2004) - et al.
Sun exposure and melanoma risk at different latitudes: a pooled analysis of 5700 cases and 7216 controls
Int J Epidemiol
(2009) - et al.
Photoadaptation to ultraviolet (UV) radiation in vivo: photoproducts in epidermal cells following UVB therapy for psoriasis
Brit J Dermatol
(2000)