Fair or freckled skin, red or blond hair and blue or green eyes: these are the common calling cards of skin cancer susceptibility. But while the risks in darker skinned people is generally reduced, it’s certainly not absent.
In Aboriginal and Torres Strait Islander people – a group with diverse, but commonly darker skin tones – melanoma and other skin cancers are less prevalent than in the non-Indigenous population, but still cause deaths every year.
Public health campaigns – think ‘slip, slop, slap’ – are often targeted to light skinned people, however the inequalities in the availability and appropriateness of health care can impact how different groups access diagnosis and treatment.
Some studies out of the US and UK suggest that, when people of colour (POC) do get skin cancers, they’re often diagnosed at a later stage and carry a higher mortality risk.
Combine this with the dearth of research on skin cancer in darkly pigmented people (studies on skin cancer in Aboriginal and Torres Strait Islanders are particularly sparse), and the picture for darker skinned people is pretty unclear.
In light of this, this article can’t offer any health advice on sun protection beyond that put forward by the Cancer Council. What it can do is look at what skin cancers are, how different types of pigmentation can change a person’s risk of skin cancer, and go over some other health considerations for sun protection in dark skin that you can bring up with your doctor.
The skin you’re in, and where it could become cancerous:
Some quick human biology: your skin is your largest organ, and is made up of the epidermis (upper layer) and the dermis (lower layer). When skin is exposed to the sun, ultraviolet (UV) rays can damage its DNA, causing the uncontrolled growth of abnormal cells.
The most common types of skin cancer all begin in the epidermis (the upper skin layer), and are handily named after the types of cells they start in:
Basal cell carcinoma (BCC): the basal cells are column-shaped and form the bottom layer of the epidermis. BCC can look like a lump or scaly patch, pale, pink or dark in colour. It’s usually slow growing, rarely spreading to other parts of the body. The earlier it’s found, the easier it is to treat.
Squamous cell carcinoma (SCC): the squamous cells are in the upper layer of the epidermis. SCC can look like a thickened scaly spot or rapidly growing lump, and tends to grow quickly. If left untreated, it can spread to other parts of the body, but this isn’t very common.
Melanoma: melanocytes are located in the basal cell layer and produce melanin pigment. Melanoma are aggressive tumors, and while this cancer is less common than BCC and SCC, it’s much more likely to spread to other parts of the body (like your brain, bones and lungs) through your lymphatic system and bloodstream.
Pigmentation – what’s it got to do with skin cancer risk?
The colour of a person’s skin is strongly influenced by their skin pigments, which are determined by their genetics and lifestyles factors, like sun exposure.
Remember those melanocytes (where melanomas form)? These cells produce melanin and package it in organelles called melanosomes. The melanin in skin comes in two main types: eumelanin is black or brown protective pigment, while pheomelanin is a yellow-red colour.
The type and amount of melanin each person produces will affect their pigmentation (skin colour). Eumelanin is abundant in darker skinned people, who produce more melanin than people with light skin.
For those among us who tan in the sun, exposure to UV rays increases the production of melanin by the melanocytes; when the melanin accumulates in the epidermal layers, a tan builds up and the skin darkens.
Melanin helps protect skin against the sun’s rays by absorbing UV radiation in the surface layers, reducing the risk of cellular DNA damage that can lead to skin cancer. This protective melanin helps reduce skin cancer risk in dark skinned people.
The flip side – dark skin and vitamin D deficiency
While this melanin barrier can protect against UV damage, it can also make it more difficult for darker skinned people to get the Vitamin D they need.
Vitamin D, known as the ‘sunshine vitamin’, is produced when our skin is exposed to ultraviolet B (UVB) light. Melanin filters this light, reducing the penetration of UVB and putting darker skinned people at a higher risk of vitamin D deficiency.
A local perspective: sun exposure and health risks for Aboriginal and Torres Strait Islander people
While the research on skin cancer in Aboriginal and Torres Strait Islanders is pretty thin on the ground, some stats published in the Australian Institute of Health and Welfare give a general picture of melanoma incidence:
Between 2005-2009, the rate for melanoma in Indigenous Australians was 9.3 cases in 100,000 people, compared to 33 cases per 100,000 in non-Indigenous Australians.
For BCC and SCC cancers, the data is extremely limited, as, unlike melanoma, these cancers aren’t mandatory to report in state and territory registries.
To gain a better understanding of what skin cancer risks are at play for the diverse Aboriginal and Torres Strait Islander population, more research is needed.
Another pressing sun-exposure-related concern is vitamin D deficiency.
In a 2014 study, one third of Aboriginal and Torres Strait Islander participants from Northern and Central Australia had vitamin D deficiency, which carries some very negative health implications: low vitamin D levels are linked to an increased risk of diseases like diabetes and heart disease.
Given the burden of these chronic diseases in Aboriginal and Torres Strait Islander people, and their contribution to a much reduced life expectancy, more research is needed on the role of sun exposure and vitamin D.
Across all aspects of the healthcare system, overcoming the disadvantage within Indigenous heath is, and needs to be, a priority – dermatology is no exception.
For more information on how to stay safe in the sun this Summer, contact Cancer Council Australia