Comment

It is too early to report the effectiveness of such policies. Where such policies have been implemented, reducing skin cancer is only one element of the policy, and other lifestyle issues tend to attract more funding. There is a need to evaluate how the implementation of sun-protection policies influences behaviour in community settings. Such studies need to be long-term randomised population studies that include specific outcome measures for each element of the policy in relation to specific target groups. Research so far shows that they have had a very limited effect in two populations and only for one or two outcome measures. Public health policy was intended to be the driver for more effective interventions and funding but so far it has been difficult to assess how effective this has been. Australia has used policies most effectively to reduce taxes on sun-protection clothing and sunscreens.

The International Agency for Research on Cancer (IARC: WHO) recently produced three separate meta-analyses - of vitamin A intake,26 carotenoids,27 and retinoids28 - and their effect on cancers, including skin cancer.28 They concluded that there was no association between the dietary intake of retinol and the risk of skin cancer in a small number of observational studies (one case-control and three cohort studies). These studies were conducted among

Caucasian populations with a wide range of disease risk. The risk estimates in the individual studies were generally greater than unity, and in every instance the 95% confidence interval (CI) included 1-0. Two prospective studies of pre-diagnostic levels of retinol and melanoma28 both reported no significant association on the basis of 30 and 10 cases, respectively. This is consistent with the findings of a case-control study of melanoma and dietary intake of preformed vitamin A.28

Evidence suggests that beta-carotene does not prevent cancer when used as a high-dose supplement and there is inadequate evidence with regard to its effect at usual dietary levels. There is inadequate evidence with respect to the possible cancer preventive activity of other individual carotenoids. This is in contrast to some results from animal studies.

A number of randomised studies have evaluated the efficacy of chemoprevention agents such as isotretinoin and beta-carotene for individuals at increased risk of developing NMSC. High-dose isotretinoin was found to prevent new skin cancers in individuals with xeroderma pigmentosum. An RCT of long-term treatment with isotretinoin in individuals previously treated for BCC showed that such treatment did not prevent re-occurrence of new BCC and produced the side-effects characteristic of isotretinoin treatment.29

An RCT of the long-term treatment with beta-carotene in individuals treated for NMSC showed no benefit for the occurrence of new NMSCs,30 concordant with the IARC meta-analysis results. For both these trials it is not known if treatment would benefit individuals at high risk (those who have sun-damaged skin) who have not yet developed skin cancer or if longer follow up would show a long-term effect in the prevention of subsequent skin cancers.

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