Study highlights how much sunshine does your body needs to cause melanoma

Washington: The researchers at the QIMR Berghofer have shown that there are 22 different genes that help to determine how much a person should be exposed to the sun before developing melanoma.

The study was published in the journal, 'British Journal of Dermatology.'

People who are at high genetic risk, sun exposure in childhood is a strong contributing factor while people at low genetic risk develop melanoma only after a lifetime of exposure to sunlight.

Australia has the highest rates of skin cancer in the world. Every year more than 12,000 Australians are diagnosed with invasive melanoma, which is the most deadly form of the disease.

Lead researcher Professor David Whiteman at QIMR Berghofer Medical Research Institute's Cancer Control Group said that in order to understand the concept well, the study used data from QSkin, the world's largest genetic study of skin cancer, to explore how genes and sun exposure affected a person's chances of developing melanomas.

"The study findings suggest that people with genes that predispose them to skin cancer only need modest levels of exposure to Australia's sunny climate to develop this disease," Whiteman said.

"Our data show that people who are born and grow up in Australia have a 50 per cent increased risk of melanomas, while those migrating to Australia as adults, who have the same genes, are less likely to develop the deadly disease.

"This confirms that sun damage up to the age of about 20 is particularly dangerous for people with a higher genetic risk because it's enough to trigger melanomas and they don't need long, cumulative exposure as well.

Adding, he said, "It's important to point out though that people who don't carry the higher risk genes associated with skin cancer can still get melanomas - they just need to get a large enough dose of sunlight over their lifetime. These people will often have lots of sunspots as a result of that exposure."

The study project manager, Catherine Olsen, said the researchers looked at genetic and behavioural factors in the data to work out melanoma risk.

"The QSkin data included information about the place of birth, age at migration, sunburns and cumulative hours spent in the sun along with histories of squamous cell carcinoma, basal cell carcinoma, and sunspots. It also included DNA information," Dr Olsen said.

"We then followed those people from 2011 and learned about their melanoma diagnoses from the Cancer Registry, which allowed us to work out risks."