Skin cancer is conventionally separated into two categories: melanoma and non-melanoma skin cancer (NMSC). Cutaneous melanoma, which comprises over 90% of all melanoma, is divided into three major histological types. The majority of melanomas in white-skinned populations are superficial spreading and nodular melanomas. Lentigo maligna melanoma (Hutchinson’s melanotic freckle) occurs later in life than the other types and more specifically on exposed sites. Acral lentiginous melanoma has not been studied epidemiologically: it is rare in white-skinned populations although it comprises a substantial proportion of melanomas in Japan[1]. Non-melanoma skin cancers are generally considered as squamous cell carcinomas (SCC) and basal cell carcinomas (BCC).

There is much more known about the epidemiology of melanoma than non-melanoma skin cancers. It is estimated that in 2000 there were 132 000 cases of melanoma diagnosed world-wide and 37 000 deaths caused by melanoma. In Europe, it is estimated that in 2000 there were 35 000 cases of melanoma diagnosed and 9000 deaths caused by melanoma. The annual world-wide melanoma burden is split unevenly between high-resource countries (104 000 cases and 25 000 deaths) and low- and medium-resource countries (28 500 cases and 12 000 deaths) [2]. The death:incidence ratio is strikingly different in these categorizations. There are no similar data available for NMSC.

The highest incidence rates of melanoma are reported from (essentially European migrant populations in) Australia and New Zealand (non-Maori population) where the annual incidence is more than double the highest rates recorded in Europe[3]. Incidence rates have been increasing rapidly for several decades in all Caucasian populations[4] although there is now an indication that in those areas where the incidence is highest, the mortality rate is beginning to stabilise or fall[5]. In Europe, during the 1990s, incidence rates were higher in northern and western Europe whereas mortality was higher in men in eastern and southern Europe. Mortality rates have been rising steadily and in Northern Europe a deceleration took place from the early 1980s. Mortality rates have also leveled off in western Europe whereas in eastern and southern Europe both incidence and mortality are still rising[6]. The net effect is that melanoma mortality rates in the mid-1990s (1993–1997) are highest in Nordic countries and lowest in southern European populations, such as Greece, Spain and Portugal[7].

There is little information systematically collected and available regarding NMSC in populations although there have been some very recent publications giving insight into the epidemiology of this topic. Although skin cancer is not unknown in children and young adults, where melanoma predominates, it is essentially a disease of ageing populations[8]. In Maastricht, the Netherlands, squamous cell cancer was the commonest form of cancer among the very elderly (aged over 95)[9].

The commonest type of NMSC is basal cell carcinoma. In Trentino, Italy, the Skin Cancer Registry calculated (for the period 1993–1998) that the incidence rate of BCC was 88 per 100 000, of SCC it was 29 per 100 000 and it was 14 per 100 000 for melanoma[10]. This tendency was confirmed in Izmir, Turkey, where nearly half the lesions appeared on the face and, while SCC was equally common in men and women, BCC were nearly three times more frequent in men[11].

In Vaud, Switzerland, BCC were the commonest form of skin cancer reported in both men and women and the incidence has been rising steadily since registration was introduced in the mid 1970s[12]. In Sweden, 39 805 SCC were registered between 1961 and 1995[12]. Incidence rates increased substantially in men (by 42%) and in women (by 146%) during this period and interpretation of mathematical models led the authors to conclude that these increases could probably be explained by increased cumulative sun exposure and increasing incidence among the elderly[13]. Between 1978 and 1995, the Slovakian Cancer Registry registered 38 629 cases of NMSC (19 600 in men and 19 029 in women). During this period, incidence rates of BCC increased by 70.4% in men and 65% in women while incidence rates of SCC increased by 13.5% in men and 18.8% in women. Head and neck were the most common sites (84.2% BCC and 74.7% SCC) followed by the trunk for BCC (17% in men and 11% in women) and upper limbs for SCC (12% in men and 12.5% in women)[14].

Mortality from NMSC is almost always from SCC, a form of cancer whose risk is strongly linked to cumulative lifetime sun exposure[15]. NMSC mortality in Europe presents an entirely different picture than melanoma. The rates are higher in men and women in southern European countries (Greece, Spain, Portugal and Italy) and low in the Nordic countries[7].

Although morbidity and mortality are low, skin cancers are far more common than other malignancies. Representative Medicare claims data were obtained from the Medicare current beneficiary survey (1992–1995) and weights were applied to give nationally representative estimates[16]. Average Medicare expenditure on cancer management was $13 billion per year and the five most costly cancers to Medicare were lung and bronchus, prostate, colon and rectum, breast and NMSC. Such considerations give NMSC a far higher public health significance than can be obtained from consideration of death statistics.

Skin cancer has several unique epidemiological features. Skin cancers range from the potentially very serious melanomas, through squamous carcinomas, to the low-morbidity and low-mortality BCC. While a patient with a primary melanoma has a 10-fold increased risk of a second primary, such second cancers are rare in absolute terms and in comparison to the many people who can have multiple BCC. Although cutaneous malignant melanoma is still a relatively rare neoplasm in many populations, incidence rates are increasing in Caucasian populations around the world. Melanoma continues to be a major public health issue given the large increases in incidence and the notable case fatality rate.

NMSC are also increasing in incidence in Caucasian populations and these trends may be exacerbated by further increases in both acute and prolonged exposure to sunshine (see Rosso et al.[15]) together with the increasing number of older people in the population. This latter observation is of crucial significance in Europe. Although the population of the (25 Member State) European Union will remain constant at around 500 million between 2000 and 2015, there will be a 22% increase in the numbers aged 65 and over and a 50% increase in those aged 80 and over[17].

Consequent to this ageing of the European population, there will be a notable increase in the number of skin cancers to be diagnosed and treated. Although not life-threatening, BCC is an important public health problem due to the frequency of the cancers and the costs of their treatment on national health resources. It is important that NMSC do not remain forgotten forms of cancer.

Skin cancer is clearly identified as one form of cancer that will become more important in public health terms in the coming decades in the absence of effective intervention today. Enough is known about the causes of skin cancers to shift the focus of population research activity from aetiology to prevention. The European Code Against Cancer [18] recommends that ‘Care must be taken to avoid excessive sun exposure. It is specifically important to protect children and adolescents. For individuals who have a tendency to burn in the sun active protective measures must be taken throughout life’. Widespread implementation of this recommendation would lead to a reduction in NMSC incidence, as has been demonstrated in Australia [19], and have a significant impact on making more resources available to treat clinical cancers, of this and other organs.

P. Boyle1*, J.-F. Doré2, P. Autier3, U. Ringborg4

1Department of Epidemiology and Biostatistics, European Institute of Oncology, Via Ripamonti 435, 20141 Milan, Italy; 2INSERM U590, 28 rue Laennec, 69373 Lyon, France; 3CRP-Santé, rue Dicks 18, 1417 Luxembourg; 4Department of Oncology, The Radiumhemmet, Karolinska Hospital/Institute, Stockholm, Sweden (*Email: director.epi@ieo.it)

Acknowledgements

It is a pleasure to acknowledge that his work was conducted within the framework of support from the Italian Association for Cancer Research (Associazone Italiana per la Ricerca sul Cancro).

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Author notes

1Department of Epidemiology and Biostatistics, European Institute of Oncology, Via Ripamonti 435, 20141 Milan, Italy; 2INSERM U590, 28 rue Laennec, 69373 Lyon, France; 3CRP-Santé, rue Dicks 18, 1417 Luxembourg; 4Department of Oncology, The Radiumhemmet, Karolinska Hospital/Institute, Stockholm, Sweden (*Email: director.epi@ieo.it)