What is the reason for the decline in melanoma rates among young Australians?

Australia is praised globally for its leadership in preventing skin cancer, which is primarily caused by ultraviolet radiation from the sun, and for the impact of national and state-based public education campaigns, including the iconic “Slip! Slap! Slop! (Seek! Slide!)” campaign.1 Other studies have focused on changing attitudes toward sunburn and sun protection behaviors, particularly among children and adolescents.2 These campaigns are recognised as a major contributing factor to the gradual decline in melanoma incidence in people under 30 years old in Australia over the past 25 years.1,3 Meanwhile, melanoma incidence continues to increase among older people in Australia, and in most other countries it is increasing across all age groups.3,4 In Australia, excessive sun exposure is a more costly risk factor than smoking when it comes to health system expenditure on cancer treatment.5 Government investment in skin cancer prevention is considered highly cost-effective, as it costs a fraction of the cost of skin cancer treatment and has a return on investment of about three times.1

It is important that health policy decisions are based on high quality, robust evidence. One methodological concern regarding the impact of skin cancer prevention campaigns is that the decline in melanoma incidence among young Australians may be due to an increasing proportion of immigrants who are at low risk of melanoma primarily due to skin pigmentation. This increase would reduce the overall risk in populations at high risk of melanoma.6

This question is addressed carefully in Whiteman et al.'s study.7 Reported in this issue servantThe authors used Australian census data on participants' parental ancestry to categorize people as at high, moderate or low risk for melanoma, and then modeled trends in the incidence of invasive melanoma by these ancestry groups from 2006 to 2021. Whiteman and his colleagues7 The ancestry-based composition of Australia's population, and therefore its melanoma risk profile, has certainly changed over time, with the proportion of people at high risk of melanoma (parents of European ancestry) declining from 85% in 2006 to 71% in 2021, while the proportion in the moderate risk (5% to 10%) and low risk categories (10% to 19%) has increased. The change in population composition was indeed associated with a decline in melanoma incidence, as more than 95% of melanomas diagnosed were in people of high-risk ancestry groups. However, it did not fully explain the decline in melanoma incidence in younger age groups. When the incidence patterns of high-risk ancestry groups were examined separately to remove the confounding effect of population change, the decline in incidence in younger age groups was still confirmed.

The decline in melanoma incidence among young people is commonly attributed to skin cancer prevention campaigns, but precise causative factors are difficult to pinpoint because successful skin cancer prevention efforts are often multifactorial and implemented in educational, recreational, and workplace settings.1,8

Whiteman and colleagues7 They hypothesize that increased screen time and less time spent outdoors may be other factors that have contributed to the decline. Changes in sunbed (indoor tanning) use over the past decade, including a ban on commercial use in Australia, may also have contributed to the decline in melanoma rates among young people.9 But Whiteman and his colleagues7 He noted that while melanoma rates are falling among young men and women in Australia and New Zealand, and among white people in the United States, women are much more likely to use tanning beds.9 Another factor that may affect incidence is that pathologists are reclassifying some melanomas as melanocytomas, which the World Health Organization classifies as a subgroup of melanocytomas intermediate between benign nevi and malignant melanomas.10 It is most commonly seen in young people.

The main conclusion of the Whiteman et al. report is7 The decline in melanoma incidence among young Australians over the past few decades can only be partly explained by migration patterns and is probably due to changes in sun exposure and protective behaviours. Given that Australia has the highest incidence of melanoma and other skin cancers,11 It is also the most expensive cancer to treat.5 Continued skin cancer prevention campaigns and other targeted efforts are essential to further reduce the burden of this highly preventable disease.