Sex matters in how, when, and where melanomas develop, study finds

Lead investigator David C. Whiteman, MBBS, PhD, Cancer Control Group, QIMR Berghofer Medical Research Institute, and Faculty of Medicine, The University of Queensland, Brisbane, Australia, explains, "There has been a general observation in numerous populations that melanomas appear to arise at different rates in men and women. We decided to investigate this observation rigorously and assess whether these differences have been constant through time or across generations by using large-scale data from population registries to investigate long-term melanoma trends in men and women.

The research team analyzed more than 40 years of melanoma data from Queensland, Australia, the USA, and Scotland. These three populations were chosen because historically they have had high (Queensland), moderate (USA), and low (Scotland) rates of melanoma. Over time, the rates of melanoma increased in all three populations, especially among women. In women in all populations, melanomas arise most commonly on the limbs, whereas in men, melanomas arise most commonly on the trunk and head and neck. In both sexes, there has been a steady increase in melanomas on the head and neck with increasing age.

Researchers found that in virtually all investigated populations, women experience higher rates of melanoma than men in early life (up to age ~45 years), but men develop melanomas at higher rates than women later in life (from ages ≥65 years). Furthermore, these sex-specific trends reflect complex patterns of incidence across body sites that vary consistently with age. Thus, in early life, women experience higher rates of lower limb melanomas than men, which persists into older ages. Also, on the upper limbs, women experience substantially higher rates than men from young ages until middle age (45-64 years), after which men experience higher rates. In contrast, on the head and neck and the trunk, melanomas occur at higher incidence in men than in women early in life. On all body sites, the rate at which melanoma incidence rises with age is much more rapid for men than for women.

The study confirms that men and women experience melanoma in different ways. While this is most likely driven by different patterns of sun exposure between men and women, there appear to be inherent differences in the ways in which melanomas develop at different body sites in women compared with men. Understanding the underlying biological differences could provide important clues about the etiology of this enigmatic cancer.

Dr. Whiteman concludes, "Invasive melanomas are potentially lethal cancers that are increasing rapidly in incidence. We need to understand how these cancers arise, and what drives their development, if we are to find better ways to prevent them. Studies like this one suggest that we may need to target our prevention efforts differently for men and women if we are to be effective in our attempts to control this cancer."