Melanoma cutáneo en una cohorte suecaepidemiología descriptiva, ocupaciones de alto riesgo y valoración del riesgo asociado a la exposición laboral a determinadas sustancias químicas por localización y sexo

Abstract

Malignant melanoma is an extremely aggressive cutaneous cancer. Although survival from this tumour tends to be high thanks to early detection of the lesions, the possibility of controlling the disease once it has metastasised is very low. On a world-wide scale, it is not a very frequent tumour, yet recently it has become increasingly relevant as a public health problem due to the sharp rise in its incidence rates in Western countries, inhabited in great measure by Caucasian populations. In recent research into the aetiology of this tumour, the hypothesis that a number of aetiopathogenic pathways may coexist, possibly differing according to the site of appearance of the lesion, is acquiring force. Nevertheless, in epidemiological research into melanoma, insufficient attention has often been paid to the importance of anatomical site, since a great number of cases is required to obtain consistent estimates, particularly if one wishes to study men and women separately. This study sought to conduct an in-depth analysis into risk by anatomical site and sex, in order to: furnish relevant information in the debate about the aetiology of melanoma; detect occupations with an increased risk of developing this tumour; and verify the risk associated with occupational exposure to certain chemical agents. To this end, a retrospective cohort study was undertaken that covered the entire, gainfully-employed Swedish population registered in the 1970 census and present in the 1960 census. This amounted to a total of 2,992,166 Swedish workers, followed up over 19 years (1971-1989) via a link with the National Cancer Registry and the Swedish Death Registry. In the first place, we studied the distribution of risk of developing melanoma: by sex and anatomical site, for general risk factors such as age, attempting to avoid the possible confounding effect of variations in time on patterns of solar exposure associated with cohort or period effects, by means of age-period-cohort models; and by socio-economic level, geographical area and size of town of residence. Our results showed that distribution of agespecific incidence rates in cutaneous melanomas of thorax was very different in men and women, suggesting the existence of an interaction with gender at this anatomical site. Furthermore, risk of developing melanoma was higher in the occupational categories corresponding to higher socio-economic power, and in larger-sized towns, except for tumours of head and neck, thereby once again indicating the specificity of risk factors by anatomical site. Secondly, this study reports the specific relative risks for each occupation, by gender and tumour site, adjusted for town size and geographical distribution. In men, significantlyhigh risks of developing cutaneous melanoma were found in some occupations exposed to artificial sources of ultraviolet radiation, e.g., lithographers and harbour masters. There was an overall excess risk of suffering from this tumour among furriers, tanners and fur dressers, patternmakers and cutters, electricity or telephone linesmen and fitters, and some workers in the glass and ceramics sector. Some of the high risks associated with specific sites in males were excess risk in: head and neck among rolling mill workers; upper limbs among chimney sweeps; and leg among pilots and aeronautical engineers. Among women, high risks of melanoma, especially in the thorax, were observed in various occupations in the educational sector. Among bank tellers, excess risk was confined to the upper limbs. Elevated risks were consistently observed in various occupations that could entail exposure to arsenic or mercury, e.g., horticultural workers, librarians, archivists and museum curators, dental hygienists, hatmakers and milliners, who registered a generalised excess risk. Other occupations with elevated risks were textile workers or telephone operators, potentially exposed to electromagnetic fields, as well as butchers and meat preparers, packers and chemical process workers. Finally, risks associated with exposure to certain chemicals were detected, using an occupation-exposure matrix purpose-designed for this Swedish cohort, in which exposure probability criteria were established for a series of chemical substances. Significantly higher risks of having melanoma were seen in both sexes, connected with the use pesticides/herbicides in general, and with short but intense use of pesticides/herbicides, both arsenical and non-arsenical, in particular. An association was also observed between this tumour and exposure to mercury, reflecting excess risk in the setting of dental surgeries. With respect to gasoline, whereas exposed women, who were mostly employed at service stations, displayed significantly high risks, overall the results for men failed to support this agent's implication in the tumour. Finally, excess risk of developing melanoma in the lower limbs was observed among women exposed to textile dust and chrome/nickel.