Sunscreen use in Childhood: Protection against Melanoma

Melanoma is a cancer arising from the malignant transformation of melanocytes. Melanoma is recognised as the 19th most common cancer worldwide, with estimated age-standardised incidence rates of 2.8–3.1 per 100,000. There is considerable variation in incidence between countries, with the highest rates reported in Australia (37 per 100,000) and the lowest in South-Central Asia (0.2 per 100,000). This trend is attributed to variations in racial skin phenotype, as well as differences in sun exposure around the world. For example, in the United States (US), 98.2% of cases are reported amongwhite-skinned individuals.

Three subtypes of melanoma can be characterize as: cutaneous melanoma (the most common) arising from melanocytes in the epidermis, mucosal melanoma from melanocytes residing in the mucous membranes and uveal melanoma from melanocytes residing in the ocular stroma.

Unfortunately the incidence of melanoma around the world has been rising annually, at a rate faster than that of any other malignancy. This is of particular concern given the unusual age demographics of the disease, Melanoma affects a higher proportion of younger patients, with a median age of diagnosis of 57 years.

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Melanoma: Epidemiology

Pigmentation has an indisputable and significant influence on skin susceptibility to malignant change. The melanocortin 1 receptor (MC1R) is a melanocyte cell-surface receptor that induces pigment production (via the signalling cascade recruitment of MITF) following activation by its ligand, alpha-melanocyte-stimulating hormone (MSH). There are many polymorphisms of the MC1R gene, resulting in the numerous skin-colour phenotypes seen in humans; variants such as the red hair, fair-skinned phenotype express low pigmentation, with a consequent increased sensitivity to ultraviolet (UV) light and associated increased melanoma risk.

The incidence of melanoma is highest in equatorial regions, and decreases with increasing distance from the equator. This directly corresponds with UV light exposure, particularly UV-B levels, and occurs regardless of skin type. Although a direct causal link has not been established, epidemiological studies have repeatedly demonstrated an association between the pattern and timing of sun exposure and melanoma. The majority of cutaneous melanomas arise on sporadically (rather than chronically) sun-exposed skin, in sites and individuals more prone to sunburn. The highest rates are seen in individuals with repeated intense sun exposure.

Sunscreen protection against melanoma

Sunscreens are used to protect the skin from the harmful effects of the sun. They help to prevent sunburn and premature aging (e.g., wrinkles, leathery skin). Sunscreens also help to decrease sunburn-like skin reactions (sun sensitivity) caused by some medications (e.g., tetracyclines, sulfa drugs, phenothiazines such as chlorpromazine). The active ingredients in sunscreens work either by absorbing the sun’s ultraviolet (UV) radiation, preventing it from reaching the deeper layers of the skin, or by reflecting the radiation.

Despite sunscreen being widely available and recommended for sun protection, optimizing the use of sunscreens remains a challenge, and controversies continue to surround its use. There have been many studies reported that shows the protective effect of sunscreens against melanoma.

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The only randomized clinical trial conducted in Australia (2011), found that regular sunscreen use was associated with a lower risk of invasive melanoma. 

A population-based case-control study in Minnesota (2011), observed a lower risk of melanoma with regular sunscreen use across 2 decades relative to nonuse. 

A population-based cohort study in Norway (2016), showed that use of sunscreens with a sun protection factor (SPF) of at least 15 was associated with a reduced risk of melanoma compared with sunscreens with a lower SPF. 

Now, a study led by University of Sydney has found that Australians aged 18-40 years who were regular users of sunscreen in childhood, reduced their risk of developing melanoma by 40 percent, compared to those who rarely used sunscreen. This is the first study to examine the association between sunscreen usages with melanoma risk in young people under 40 years. The data was collected from nearly 1700 people who participated in the Australian Melanoma Family Study. The association of sun exposure and sunburn with melanoma risk, particularly in childhood, is well established and this study showed that regularly using sunscreen was protective against the harmful effects of sun exposure.

Sunscreen Use and Melanoma Risk Among Young Australian Adults. JAMA Dermatology, 2018

This study confirms that sunscreen is an effective form of sun protection and reduces the risk of developing melanoma as a young adult. Sunscreen should be applied regularly during childhood and throughout adulthood whenever the UV Index is 3 or above, to reduce risk of developing melanoma and other skin cancers.

©BforBiotech by Bedadyuti Mohanty, Assistant Managing Editor by Profession and Bio-technologist by heart.

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