Skin cancer may up risk of other cancers

People who have had common skin cancers may be at an increased risk of developing melanoma and 29 other cancer types, a new study has warned.
Individuals who had nonmelanoma skin cancer (NMSC) were at increased risk for subsequently developing other cancer types, and this association was much higher for those under 25 years of age, researchers said.
NMSC is the most common type of skin cancer. It is relatively easy to treat if detected early, and rarely spreads to other organs, they said.
"Our study shows that NMSC susceptibility is an important indicator of susceptibility to malignant tumours and that the risk is especially high among people who develop NMSC at a young age," said Rodney Sinclair, professor of medicine at the University of Melbourne in Australia.

"The risk increases for a large group of seemingly unrelated cancers; however, the greatest risk relates to other cancers induced by sunlight, such as melanoma," said Sinclair.
Compared with people who did not have NMSC, those who did were 1.36 times more likely to subsequently develop any cancer, including melanoma and salivary gland, bone, and upper gastrointestinal cancers.

Survivors younger than 25 years of age, however, were 23 times more likely to develop any cancer other than NMSC.
In particular, they were 94 and 93 times more likely to get melanoma and salivary gland cancer, respectively.
"Our study identifies people who receive a diagnosis of NMSC at a young age as being at increased risk for cancer and, therefore, as a group who could benefit from screening for internal malignancy," said Sinclair.

Researchers hypothesised that people who develop skin cancers later in life do so as a result of accumulated Sun exposure, while those who develop skin cancer at a younger age may do so as a result of an increased susceptibility to cancer in general.
To investigate this, they stratified the risk ratios by age and discovered that young people with NMSC are more cancer-prone.
The researchers constructed two cohorts: one of 502,490 people with a history of NMSC, and a cohort of 8,787,513 people who served as controls.
They followed up with the participants electronically for five to six years, and 67,148 from the NMSC cohort and 863,441 from the control group subsequently developed cancers.

They found that for those who had NMSC, the relative risk for developing cancers of the bladder, brain, breast, colon, liver, lung, pancreas, prostate, and stomach remained consistently elevated for the entire period of the study, and the risk for cancers of the brain, colon, and prostate increased with time.
The study was published in the journal Cancer Epidemiology, Bio-markers & Prevention.