Melanoma can be prevented
The concern of the Cancer Registry of Norway about the increase in melanoma incidence must be taken seriously. Why has it increased in the last decade – after showing a falling or non-rising tendency in the 1990s? The increase was most pronounced in the cohorts aged over 50, and among men (19).
The reason is presumably a change in sunbathing habits. People aged over 50 undress more than they used to; they holiday in sunny regions, and men use less sun protection than women (19). The most recent meta-analysis (9) found that melanoma risk increases with the number of sunburns throughout a person's life. Reduced exposure in adulthood can reduce the risk.
Unfortunately, it is easy for the young to ignore the fact that excessive tanning, out of doors and in solariums, may result in a higher risk of melanoma in later life. The meta-analyses indicate that indoor tanning in one's youth is associated with a higher risk than use later in life (Table 2). In our study of Norwegian and Swedish women, we found that the risk increased when solarium use extended over several decades (20).
Although some estimates of relative risk are less than 1 for chronic sun exposure (Table 1), it is unlikely that this indicates protection against melanoma. The individuals in question are often outdoor workers with occupational exposure. The reference category (lowest category of chronic sun exposure) may include a mixture of individuals with high and individuals with low intermittent exposure, with the result that the effect estimate may be artificially low (10).
It is relatively simple to urge people to avoid sunburn, and sunburn has been an important and measurable variable in cancer prevention for over 20 years. Nevertheless, the incidence of sunburn is still high in Norway and many other countries (21) – (23). Sun safety rules, both in Norway (24) and abroad (e.g. the USA) (25), recommend taking breaks from the sun – staying in the shade and using clothing and a hat rather than sunscreen. These measures may be more effective than sunscreen for providing protection against sunburn (22).
Avoiding excessive sun exposure is not in conflict with the fact that the sun is our most important source of vitamin D. The Norwegian Cancer Society’s sun safety recommendations start by stating that sun protection does not mean totally avoiding the sun (24).
Indoor tanning is not recommended. On average, Norwegian solariums emit twice as much UVB radiation and around six times as much UVA radiation as the Oslo summer sun (26). Both UVB and UVA radiation are classified as carcinogenic (13). Studies from the last 30 years indicate that there is a 16 % higher risk of melanoma associated with ever having used a solarium, and a 34 % higher risk associated with having used a solarium more than ten times, compared with never (Table 2).
A recent American study found that indoor tanning is a risk factor for melanoma even among individuals who had never experienced burns from either indoor tanning or outdoor sun exposure (27). It is estimated that 5.8 % of the melanoma cases diagnosed each year among men and 9.4 % of cases among women can be attributed to use of solariums (population attributable risk, Norway) (15). These cases could have been avoided.
The new report from the Office of the Surgeon General of the USA has been cited (23). In it, a broad array of players are urged to start primary preventive measures against skin cancer. Five strategic goals were described:
Increase opportunities for sun protection in outdoor settings
Provide individuals with the information they need to make informed, healthy choices about UV exposure (from sun and solarium)
Promote policies that advance the national goal of preventing skin cancer
Reduce harm from indoor tanning
Strengthen research, surveillance, monitoring and evaluation relating to skin cancer prevention