Australian Study Finds A Complex Association Between Sun Exposure And Skin Cancers

Skin cancers are one of the most common cancers among fair-skinned people worldwide. Although the type of skin cancer varies among persons and from region to region, a population-based study carried out by Subramaniam, PD and colleagues from Queensland University of Technology, Australia has indicated that basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) have anatomical restrictions and are caused in specific regions of the body only.

Basal cell carcinoma and squamous cells carcinoma are two types of keratinocyte cancer (KC), also known as non-melanoma skin cancer (NMSC). BCCs are abnormal, uncontrolled growth of cancer cells in the deep layers off epidermis.
The tumors never spreads from where it starts and only in rare cases does it spread to other parts of the body. The tumors appear as red patches, shiny bumps and open sores.

In contrast, SCCs are tumor growth in the upper layers of epidermis. They have to be treated at once because they become disfiguring and deadly at times. They appear as elevated growths on the skin surface in the form of warts and they may crust or bleed.

In addition, BCCs have a tendency to occur on the head, neck and trunk while SCCs commonly occur on the hands, back and buttocks.

The Skin Cancer Foundation reports that BCC is the most common form of cancer while SCC is the second most common form of cancer. According to experts, BCC accounts for 80% of KC cases while SCC accounts for 20% of KC cases.

As fair skinned people are sensitive to sunlight, Australians are particularly susceptible to skin cancer. The Cancer Council of Australia reports that 32.6% of cancer cases were of skin cancers and records show that there were 950,000 KC cases in 2011-2012 which were treated by paid Medicare services.

In contrast, over 5.4 million cases of non-melanoma skin cancer are treated in more than 3.3 million people in the United States. From these statistics, BCC accounts for 4 million cases while SCC accounts for 1 million cases of skin cancer.

The data of the study was taken from the population-based QSKin Sun and Health Study in Queensland, Australia. The national medical insurance records showed that out of 37103 participants, 3398 were diagnosed with KCs from September 1, 2010 to September 30, 2012.

The QSKin Sun and Health Study was a cohort study carried out in 2011 by randomly selecting participants in Queensland. The purpose of the study was to analyze skin cancer and melanoma in the population.

The scientists calculated the relative tumor densities (RTDs) on certain body regions and calculated the rate of occurrence by dividing the proportion of tumors at a specific site by the proportion of skin area of that specific site.

The data indicated that a total of 5150 KCs were identified in 2374 participants out of which 1339 were men and 1035 were women. Out of these, 3846 (74.7%) KC cases were BCCs while the remaining were SCCs.

Analysis of the data confirmed that 1547 (40.2%) of BCCs were on the head and neck region while 1305 (33.9%) of BCCs were on the truck region. In contrast, 435 (33.4%) of SCCs were on the head and neck region and 455 (34.9%) of SCCs were on the upper limbs.

The difference in RTDs between BCC and SCC on the hands was with an occurrence ratio of 1:14 and on the back and buttocks with an occurrence ratio of 8:1. Moreover, RTDs of KCs on the scalp and ear region were higher in men when compared to women while RTDs on the upper arm region was higher in women when compared to men.

The study, titled “Anatomical Distributions of Basal Cell Carcinoma and Squamous Cell Carcinoma in a Population-Based Study in Queensland, Australia”, was published in JAMA Dermatology on November 23, 2016.

The scientists concluded that sun exposure is the primary cause of high RTDs for BCC and SCC tumors. However when it came to BCCs, high RTD on less sun-exposed areas and low RTD on the hands suggested a complex association of keratinocyte cancers with sun-exposure.

When it comes to sun-exposure, it is the cause of around 99% of non-melanoma skin cancers and 95% of melanomas in Australia. The Cancer Council of Australia reports that Australians have been seeking sun-exposure over summer due to concerns of vitamin D deficiency although 77% of Australians are not vitamin D deficient.

Therefore, experts recommend Australians not to expose themselves to sunlight needlessly as they can get adequate sunlight from day to day activities, such as walking outside for a couple of minutes to the car or the shop.

The experts however say that if you are going outside for more than a few minutes and the UV Index is 3 or above, you need to protect yourself with sun shades, sunscreens, hats, clothing and sunglasses.

However, if the UV Index is below 3, as in autumn and winter, sun protection is not needed. Experts recommend people go out of doors in the middle of the day on most days of the week with some skin uncovered.

The reason is that too much sun exposure increases the risks of skin cancer is that UV radiation damages the genetic material in skin cells. Basically, the skin becomes injured and the blood around the injured skin rushes in, causing the skin to look red.

Although the body repairs most of the damage, continuous exposure to UV rays causes some cells to remain damaged and as a result they starts growing out of control which leads to skin cancer.

Sometimes the sun damage is so severe that the cells have to be destroyed. This can cause peeling which is the body’s way of getting rid of dead cells. This could also lead to cancer.

Medical services of a person costs an average of AUD $2756 while the cost of medical services of persons with keratinocyte cancers costs an average of AUD $2756, indicating that persons diagnosed with KCs spend an additional AUD $1436 on medical treatments and services.

In addition, Australians are particularly at risk of skin cancer because after Africa, Australia is the sunniest place on Earth. According to statistics by ABC Australia gets an average of 5.73 kWh/m2 of sunlight per day while North America gets about 3.89 kWh/m2 of sunlight per day.

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