Comparison of the site distribution of melanoma in New Zealand and Canada

Abstract

A comparison of the site distribution of cutaneous malignant melanoma in New Zealand and Canada was performed. This series deals with 41,331 incident cases registered between 1968 and 1990 and is the largest to date to evaluate the influence of age and gender on the site distribution of melanoma. Site-specific, age-standardized rates per unit surface area and relative tumour density were assessed by gender and country and differences compared with statistical techniques adapted to this context. The age-standardized rates for all sites were higher in New Zealand than in Canada, the ratio being 3.2 for men and 3.8 for women. Occurrence of melanoma was denser for chronically than intermittently exposed sites in both New Zealand and Canada. The highest incidence rate per unit area was for the ears in men which was more than 5 times the rate for the entire body in each country. For each gender, melanomas were relatively commoner on the trunk and the face in Canada, and on the lower limbs in New Zealand. The variations in the site distribution were similar in each country and consistent with the effect of differential patterns of sun exposure between genders. Our results show that the levels of risk of melanoma between phenotypically comparable populations exposed to different amount of UV radiation vary in a site-specific manner, especially for intermittently exposed sites. This suggests that both environmental conditions and lifestyle factors influence the site distribution of melanoma in these two populations. Although exposure to ultraviolet radiation (UVR) has been identified as the chief environmental risk factor for skin cancer among Caucasians (IARC, 1992), the aetiology of cutaneous malignant melanoma (hereafter referred to as melanoma) is not fully understood. The site distribution of melanoma has been important in generating aetiological hypotheses about the disease. As determinants of the anatomical site distribution have not yet been elucidated, some speculation has occurred about the mode of the carcinogenic process involved (Lee and Merrill, 1970;Green, 1992).Unlike squamous cell carcinoma and, to a lesser extent, basal cell carcinoma which are strongly associated with UVR and frequently observed on heavily exposed sites such as the face and the neck, the back of the hands and the forearms (Pearl and Scott, 1986;Levi et al., 1988;Osterlind et al., 1988;Kaldor et al., 1993), melanoma has long been known to occur commonly on less sun-exposed sites, such as the trunk for men and the lower limbs for women (Lee and Yongchaiyudha, 1971;Davis, 1976;Crombie, 1981). However, when differences in surface area between anatomical parts of the body were considered, risks of the same order of magnitude have generally been reported for melanoma occurring on chronically and intermittently exposed sites, although substantial variation existed between studies (Elwood and Lee, 1975;Elwood and Gallagher, 1983;Pearl and Scott, 1986;Osterlind et al., 1988;Green et al., 1993;Franceschi et al., 1996). The occurrence of melanoma...

A comparison of the anatomic distribution of cutaneous melanoma in two populations with different levels of sunlight: the west of Scotland and Queensland, Australia 1982–2001

“…The same relative sparing of melanoma on the torso and upper limbs seen in Scottish women and the same relatively high incidence on the lower limbs has been reported in women in both Canada [18] and New Zealand [19]. Though there are no age-and site-specific melanoma data available for men in the other temperate populations, the overall site-specific incidence rates reported for Canada and New Zealand [18][19][20] are comparable to those seen here for Scotland. Melanoma incidence rates on the limbs have been analyzed in detail for the populations of two other eastern Australian states, New South Wales and Victoria, and patterns were shown to be the same as in Queensland, although relative magnitudes showed the expected latitude dependence [21].…”

An analysis of risk factors for cutaneous melanoma by anatomical site (Australia)

“…The high incidence of cutaneous melanomas on some relatively unexposed body sites (such as the lower limbs in females) contrasts with the paucity of melanomas on some habitually exposed sites (such as the forearms and dorsum of the hand), indicating that site-specific differences in melanoma development are likely to exist [16]. Moreover, the incidence of melanomas of the trunk peaks before that of the head and neck, even after accounting for the underlying effects of birth cohort and time period on melanoma rates [13,15,[17][18][19][20]. These descriptive observations suggest that melanomas develop through different pathways depending upon their anatomical location, for which there is some support from analytical epidemiological studies.…”

Changes in the incidence of cutaneous melanoma in the west of Scotland and Queensland, Australia: hope for health promotion?

“…To our knowledge, no comparable investigations have been conducted previously, yet such information is necessary for monitoring the impact of prevention strategies across populations. Previous analytical comparisons between populations with high versus low rates of melanoma have not systematically compared rates of change of incidence, but have rather described different patterns of anatomical distribution (Bulliard et al, 1997), histological characteristics (Garbe et al, 2000) or overall mortality (Severi et al, 2000). Such analyses have provided useful insights into causal models and the effectiveness of early detection and treatment; however, inferences regarding the prevention of melanoma are not possible from those data.…”