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Sorting the hype from the facts in melanoma
FEATURE
Sorting the hype from the facts in melanoma critical risk factor for melanoma pattern. In other words, for a given he global incidence of melanoma but may be a marker for a yearly exposure to sunlight of say 100 has been rising since the 1920s, combination of a susceptible skin hours, the intermittent dose received but researchers remain in the dark type and excessive sun exposure. by an office worker on holiday is about many aspects of the disease. Data are now starting to appear far riskier in terms of melanoma There is no good animal model for on sunscreen effectiveness. Although development than the regular dose melanoma, so the main source of some case-control studies, which received by an outdoor worker. information is epidemiology and here inevitably suffer from recall bias, have Researchers are now puzzling over the data are complex and baffling. shown that sunscreens reduce the risk how regular (as opposed to interIn the past 12 months, researchers of melanoma, some show no effect, mittent) exposure could be associhave sparked controversy by speaking and some suggest that sunscreens ated with less risk of developing openly of uncertainties in the increase melanoma rates. But in melanoma, but not with less risk of epidemiological data. The increasing some studies, wearing a hat has also developing squamous-cell carcinoma incidence of melanoma is generally been associated with an increased (whose precursor cells lie in the attributed to the fashion for tanned melanoma risk. Epidemiologists same skin layer as melanocytes), and skin, and public-health campaigns blame confounders for this sort of whether there is such a thing as a have urged people to stay out of the unlikely result. People who are at “safe tan”, explains epidemiologist sun, use sunscreens, and avoid sunhighest risk for melanoma—the sunGraham Giles (Anti-Cancer Council burn. But the epidemiological data sensitive and the sun-loving—are of Victoria, Australia). gathered since the 1980s provide most likely to use sunscreens, little support for these edicts Sun exposure and melanoma risk—a speculative model says Armstrong. “The effect of —continuous sun exposure sunscreens would have to seems to be safer than interNB: slope of lines is not known be very large to offset the mittent exposure; the evidence Reduce risk [confounding] effects of sunthat burning is a specific cause by changing pattern sensitivity and sun exposure.” of melanoma is shaky; and e dos ing The falling rates of melanoma there is no direct evidence that wer o l by in cohorts born after the 1950s sunscreens are protective. sk i r uce indicate that sunscreens may Red These messages of uncerIntermittent sun exposure—eg, indoor worker be having an effect, he adds. tainty from Jonathan Rees, Continuous sun Meanwhile, although there professor of dermatology at exposure—eg, outdoor worker is no good animal model for Newcastle University, UK, Exposure to sunlight (hours) melanoma, work by Vivienne and from Marianne Berwick Reeve (Sydney University, (Memorial Sloan Kettering Australia) and others has shown that Robin Marks, professor of dermaCancer Center, NY, USA) were sunscreens reduce the incidence of tology at Melbourne University, transformed by the media into claims squamous-cell carcinoma in the hairAustralia, is among those who believe that the “cancer danger from the sun less mouse. In addition, Marks has that there is no such thing as a safe is a myth” and that sunscreen shown that sunscreen protects people tan. “It’s the desire to get a tan that producers were perpetrating a conagainst the development of solar kerresulted in the melanoma escalation spiracy. And to Rees and Berwick’s atoses—believed to be the precursors seen in the 1980s”, he says. horror, their comments were seen by of squamous-cell carcinoma. But failArmstrong agrees that the idea of a some as vindicating solariums. “We ure to burn does not eliminate cancer safe tan could be dangerous. It is are all reacting to the complexity risk, warns Reeve. Mice that get half theoretically possible that risk might of melanoma”, says Berwick. “The the dose that causes burning still be reduced if the overall dose were problem is we simply don’t know develop half the number of cancers. held steady but the pattern changed how to interpret the data.” Given all the uncertainties, it is not from intermittent to continuous Melanoma risk clearly increases surprising that there is disagreement exposure, but, “that is not what with sun exposure—one need only on what to tell the public. Rees people are readily able or likely to compare the five to eight-fold higher believes that year-round use of sundo”, so Armstrong advocates lowermelanoma rates in Australia comscreens is inappropriate in the UK ing risk by minimising the dose. pared with the UK. But the risk also where the ultraviolet intensity is The role of sunburn in melanoma depends on exposure pattern. Studies much less than in Australia, particudevelopment is also contentious. in the 1970s by Bruce Armstrong and larly as “the role of sunlight in Case-control studies suggest that the colleagues in western Australia were increasing vitamin D levels in some number of episodes of sunburn is a among the first to show that indoor groups in the UK is more critical strong risk factor, but Dallas English workers are at higher risk of than in Australia”. Marks’ message is (University of Western Australia, melanoma than outdoor workers. that people should not spend more Perth) and Berwick say these studies This, and the high melanoma incitime in the sun just because they are are unreliable. English and Berwick dence on areas exposed to the sun wearing sunscreen that may even have found that patients asked about only occasionally, supports the idea place them at higher risk. And their sunburn history give different that intermittent exposure might be Berwick urges people to take account answers at different times. And, when riskier than regular exposure. Indeed, of their personal risk factors such as skin type was added in, Berwick many studies have shown that while skin type and number of moles before found that the link between the risk of squamous-cell carcinoma deciding how long to sit in the sun. melanoma and sunburn became less increases sharply with increasing sun significant. Based on these results, exposure, intermittent or otherwise, she says that sunburn may not be the melanoma risk depends on exposure Elizabeth Finkel Risk of melanoma
T
1866
THE LANCET • Vol 351 • June 20, 1998
Sorting the hype from the facts in melanoma critical risk factor for melanoma pattern. In other words, for a given he global incidence of melanoma but may be a marker for a yearly exposure to sunlight of say 100 has been rising since the 1920s, combination of a susceptible skin hours, the intermittent dose received but researchers remain in the dark type and excessive sun exposure. by an office worker on holiday is about many aspects of the disease. Data are now starting to appear far riskier in terms of melanoma There is no good animal model for on sunscreen effectiveness. Although development than the regular dose melanoma, so the main source of some case-control studies, which received by an outdoor worker. information is epidemiology and here inevitably suffer from recall bias, have Researchers are now puzzling over the data are complex and baffling. shown that sunscreens reduce the risk how regular (as opposed to interIn the past 12 months, researchers of melanoma, some show no effect, mittent) exposure could be associhave sparked controversy by speaking and some suggest that sunscreens ated with less risk of developing openly of uncertainties in the increase melanoma rates. But in melanoma, but not with less risk of epidemiological data. The increasing some studies, wearing a hat has also developing squamous-cell carcinoma incidence of melanoma is generally been associated with an increased (whose precursor cells lie in the attributed to the fashion for tanned melanoma risk. Epidemiologists same skin layer as melanocytes), and skin, and public-health campaigns blame confounders for this sort of whether there is such a thing as a have urged people to stay out of the unlikely result. People who are at “safe tan”, explains epidemiologist sun, use sunscreens, and avoid sunhighest risk for melanoma—the sunGraham Giles (Anti-Cancer Council burn. But the epidemiological data sensitive and the sun-loving—are of Victoria, Australia). gathered since the 1980s provide most likely to use sunscreens, little support for these edicts Sun exposure and melanoma risk—a speculative model says Armstrong. “The effect of —continuous sun exposure sunscreens would have to seems to be safer than interNB: slope of lines is not known be very large to offset the mittent exposure; the evidence Reduce risk [confounding] effects of sunthat burning is a specific cause by changing pattern sensitivity and sun exposure.” of melanoma is shaky; and e dos ing The falling rates of melanoma there is no direct evidence that wer o l by in cohorts born after the 1950s sunscreens are protective. sk i r uce indicate that sunscreens may Red These messages of uncerIntermittent sun exposure—eg, indoor worker be having an effect, he adds. tainty from Jonathan Rees, Continuous sun Meanwhile, although there professor of dermatology at exposure—eg, outdoor worker is no good animal model for Newcastle University, UK, Exposure to sunlight (hours) melanoma, work by Vivienne and from Marianne Berwick Reeve (Sydney University, (Memorial Sloan Kettering Australia) and others has shown that Robin Marks, professor of dermaCancer Center, NY, USA) were sunscreens reduce the incidence of tology at Melbourne University, transformed by the media into claims squamous-cell carcinoma in the hairAustralia, is among those who believe that the “cancer danger from the sun less mouse. In addition, Marks has that there is no such thing as a safe is a myth” and that sunscreen shown that sunscreen protects people tan. “It’s the desire to get a tan that producers were perpetrating a conagainst the development of solar kerresulted in the melanoma escalation spiracy. And to Rees and Berwick’s atoses—believed to be the precursors seen in the 1980s”, he says. horror, their comments were seen by of squamous-cell carcinoma. But failArmstrong agrees that the idea of a some as vindicating solariums. “We ure to burn does not eliminate cancer safe tan could be dangerous. It is are all reacting to the complexity risk, warns Reeve. Mice that get half theoretically possible that risk might of melanoma”, says Berwick. “The the dose that causes burning still be reduced if the overall dose were problem is we simply don’t know develop half the number of cancers. held steady but the pattern changed how to interpret the data.” Given all the uncertainties, it is not from intermittent to continuous Melanoma risk clearly increases surprising that there is disagreement exposure, but, “that is not what with sun exposure—one need only on what to tell the public. Rees people are readily able or likely to compare the five to eight-fold higher believes that year-round use of sundo”, so Armstrong advocates lowermelanoma rates in Australia comscreens is inappropriate in the UK ing risk by minimising the dose. pared with the UK. But the risk also where the ultraviolet intensity is The role of sunburn in melanoma depends on exposure pattern. Studies much less than in Australia, particudevelopment is also contentious. in the 1970s by Bruce Armstrong and larly as “the role of sunlight in Case-control studies suggest that the colleagues in western Australia were increasing vitamin D levels in some number of episodes of sunburn is a among the first to show that indoor groups in the UK is more critical strong risk factor, but Dallas English workers are at higher risk of than in Australia”. Marks’ message is (University of Western Australia, melanoma than outdoor workers. that people should not spend more Perth) and Berwick say these studies This, and the high melanoma incitime in the sun just because they are are unreliable. English and Berwick dence on areas exposed to the sun wearing sunscreen that may even have found that patients asked about only occasionally, supports the idea place them at higher risk. And their sunburn history give different that intermittent exposure might be Berwick urges people to take account answers at different times. And, when riskier than regular exposure. Indeed, of their personal risk factors such as skin type was added in, Berwick many studies have shown that while skin type and number of moles before found that the link between the risk of squamous-cell carcinoma deciding how long to sit in the sun. melanoma and sunburn became less increases sharply with increasing sun significant. Based on these results, exposure, intermittent or otherwise, she says that sunburn may not be the melanoma risk depends on exposure Elizabeth Finkel Risk of melanoma
T
1866
THE LANCET • Vol 351 • June 20, 1998