Half of all cancers in the United States are skin cancers. We have previously shown in a 4.5-year randomized controlled trial in an Australian community that squamous cell carcinomas (SCC) but not basal cell carcinomas (BCC) can be prevented by regular sunscreen application to the head, neck, hands, and forearms. Since cessation of the trial, we have followed participants for a further 8 years to evaluate possible latency of preventive effect on BCCs and SCCs. After prolonged follow-up, BCC tumor rates tended to decrease but not significantly in people formerly randomized to daily sunscreen use compared with those not applying sunscreen daily. By contrast, corresponding SCC tumor rates were significantly decreased by almost 40% during the entire follow-up period (rate ratio, 0.62; 95% confidence interval, 0.38-0.99). Regular application of sunscreen has prolonged preventive effects on SCC but with no clear benefit in reducing BCC.
"Green's study did not mention the actual amounts of sunscreen applied, but with a SPF 16 sunscreen and the realistic amounts used by the subjects, the actual SPF obtained was likely exponentially lower than 16. The other form of blatant sunscreen misuse in Green's study was the fact that in the daily sunscreen group, 75% of patients were applying sunscreen to parts of their body 3-4 days per week, and this was supported by measured sunscreen weights . In the “daily” group, 75% of the subjects were using sunscreen roughly 50% of the time, and one may consider that more consistent use of the daily assignment may have yielded different results. "
[Show abstract][Hide abstract] ABSTRACT: Basal cell carcinoma (BCC) is the most common human malignancy. Both epidemiological and direct evidence have established ultraviolet (UV) exposure from the sun as the most important risk factor for BCC development. There has only been one randomized and controlled study to examine sunscreen's role in the prevention of BCC, and no significant protective benefit was found. This study did not address four important concepts: sunscreen abuse, sunscreen misuse, sunscreen formulation, and cumulative UV exposure. Thus, the results of this study are difficult to interpret and extrapolate with real-world sunscreen practices.
"Regular sunscreen use has been shown to reduce the occurrence of SCC in this study population [22,33], and thus we routinely adjusted for treatment allocation in all analyses. The known influence of fair skin on both sunscreen use and skin cancer  was also accounted for in all analyses and should not have affected results. "
[Show abstract][Hide abstract] ABSTRACT: The relationship between physical activity and risk of cutaneous squamous cell carcinoma (SCC) is unknown and difficult to investigate due to confounding by sun exposure. We prospectively examined the association of recreational and occupational physical activity and incidence of SCC accounting for photoaging and other risk factors.
We used available information on physical activity from the Australian population-based Nambour Skin Cancer Study comprising 1,171 adults aged 25-75 years at baseline (1992). In sex-stratified analyses (person-based and tumor-based) we estimated the associations between type of activity and incidence of SCC prospectively to 2007.
During 16 years of follow-up, 98 men and 90 women newly developed SCC. We found no significant association between recreational activity measures and SCC after controlling for potential confounding factors including indicators of sun exposure. In men, the observed risk pattern was however suggestive of elevated risk with increasing total hours of recreational activity (compared to inactive men, RR (95%CI) 0.89 (0.54, 1.46) for ≤ 1.5 hrs/wk; 1.29 (0.82, 2.04) for ≤ 4.0 hrs/wk; 1.33 (0.86, 2.05) > 4.0 hrs/wk), while among women, higher level of occupational activity (standing and manual versus sedentary work activities) was associated with a reduced incidence of SCC tumors (P trend = 0.03).
Despite some suggestion that recreational activity in men and occupational activity in women are related to occurrence of SCC, there is no firm support for a role of physical activity in the development of cutaneous SCC.
BMC Cancer 12/2011; 11:516. DOI:10.1186/1471-2407-11-516 · 3.36 Impact Factor
"Sunscreen use is widely advocated by public health bodies as a means of reducing the risk of skin cancer, especially in sun-sensitive skin types I and II. However, there is no evidence that sunscreens prevent malignant melanoma (MM) , some evidence that they may prevent basal cell carcinoma (BCC) , but there is good evidence that they prevent squamous cell carcinoma (SCC) . Sunscreens would be expected to offer some protection against SCC because the action spectrum for this lesion, based on mouse data, is quite similar to that for human erythema. "
[Show abstract][Hide abstract] ABSTRACT: The adverse effects of solar ultraviolet radiation on the skin are well documented, especially in fair-skinned people. These can be ameliorated by photoprotection strategies advocated by many public health bodies and typically include sun avoidance, sunscreen use and clothing. The UVB waveband which is the main cause of all adverse effects investigated in the laboratory to date is also the waveband for vitamin D photosynthesis which is the only established benefit of solar exposure. This is especially important because solar UVB is the main source of vitamin D for most people. There is increasing evidence that vitamin D plays a much greater role in human health than was previously thought. This has given rise to concerns that photoprotection, especially sunscreen use, could adversely affect vitamin D status and human health. Furthermore, it is stated that people with heavily pigmented skins often have poor vitamin D status because of photoprotection by melanin. In this paper we review the effect of photoprotection strategies and pigmentation on vitamin D status. Clothing can clearly be very effective at inhibiting vitamin D synthesis. Sunscreens are effective in theory and some limited human studies support this. However, most studies show little or no effect and the most likely reason for this is that sunscreens have not been applied in the manner that was used to determine their labelled index of protection against sunburn. This could change in the future if public health campaigns and the sunscreen industry are successful in encouraging the public to apply sunscreens more liberally and/or use much higher levels of labelled protection. The role of melanin on vitamin D status is not clear and requires further investigation.
Journal of photochemistry and photobiology. B, Biology 03/2010; 101(2):160-8. DOI:10.1016/j.jphotobiol.2010.03.006 · 2.96 Impact Factor
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