Researchers who followed skin cancer survivors for 16 years have concluded that they are twice as likely as people without skin cancer to develop another form of cancer later on.
The new study, from Johns Hopkins and the Medical University of South Carolina, tracked 769 patients who had non-melanoma skin cancer -- the most common form in the United States -- and 18,405 people who had not had the illness and found that those who had skin cancer were twice as likely to develop another form.
Among the cancers skin cancer survivors would ultimately contract, melanoma was by far the most common, with eight times the risk. The researchers also found that these people experienced an increased risk for lung, colorectal, breast, and prostate cancers.
The news could be enough to give pause to millions of Americans who have battled skin cancer in the past -- among them Republican presidential candidate Sen. John McCain. McCain has weathered six instances of non-melanoma skin cancer, the type studied in the research.
However, the findings of higher cancer rates were most prominent among the youngest skin cancer patients in the study, who were between the ages of 25 and 44, so they are unlikely to have much bearing, if any, on the nation's most famous skin cancer survivor, who turns 72 Friday.
Although the findings are considered preliminary, part of the reason for this, the researchers speculate, is that the findings indicate that people's DNA have different repair abilities, which make some less able to repair damage from environmental irritants and more likely to develop cancer.
But in McCain's case, the origins of his skin cancer are likely from exposure to sunlight in his environment.
"I think if someone -- like John McCain, for example -- has very fair skin, light eyes and a history of living in a place like Arizona, that is a darn good explanation for his skin cancers, and he is healthy otherwise … so the chances of his non-melanoma skin cancers being a marker for other DNA repair problems is slim in my opinion," said Dr. Mark Abdelmalek, a regular contributor to ABC News, who reviewed McCain's health records on behalf of ABC when they were released in May.
But for others, the new research could offer intriguing hints to the origin of their skin cancers -- and perhaps one day an early warning of future risk.
"A personal history of non-melanoma skin cancer may be more a part of personal health history than we thought before," said Anthony Alberg, associate director for cancer prevention and control at the Hollings Cancer Center of MUSC and one of the study's lead authors.
For the study, skin cancer records were taken from a registry in Washington County, Md., and subjects gave demographic information at the beginning of the study, before their health histories were tracked for the next 16 years.
The study appears in the newest issue of the Journal of the National Cancer Institute.
While some are calling the findings promising, Alberg stresses that they probably won't affect the clinic at this time.
"It's too early to know what to do with this information," he said.
While avoiding skin cancer earlier by using sunscreen and avoiding exposure might not necessarily reduce later cancer risks, Alberg noted that, "Taking steps to avoid non-melanoma skin cancer would be wise anyway."
Margaret Karagas, associate director of the Center for Environmental Health Sciences at Dartmouth Medical School, said that this study could provide a model for future cancer research, noting that many discoveries about cancer that are applied to different types originated with skin cancer research.
"Skin cancer has been a useful model of carcinogen discovery," she said, listing radiation and arsenic among the cancer-causing agents that were initially discovered because they caused skin cancers.
"It's also important because in many parts of the world it appears to be one of the most rapidly increasing cancers," she said.
Alberg also noted that non-melanoma skin cancer may provide a better initial marker because any subsequent cancers are unlikely to be caused by the treatment.
"Non-melanoma skin cancer avoids [these problems] because it is locally treated, and so there aren't late effects of treatment like you might see with melanoma."
While he said the findings were interesting, Abdelmalek said he would be reluctant to use this information in his practice.
"The idea is fine to think about. You don't want to think of skin cancer as a separate issue that has nothing to do with the rest of the body," he said.
He noted that for many patients, however, there were other explanations for their cancers that the study did not adequately address. One problem he said he found was that patients' history of sun exposure was based on their own recall over 10 years after the study began.
"Relying on a patient's history to accurately report their sun exposure is a joke," he said. "You have no idea how many people will tell me they don't go out in the sun when they have a tan line glaring at me and their back is peeling from a recent sunburn."
He said that these warnings might not be helpful.
"The data can't really say which types of other malignancies are associated," he said. "So what do you tell people? 'You may get another cancer, but it's a crap shoot as to where?'"
While he sees promise in these findings for helping younger patients assess their future cancer risk, in older patients, he said, you have much more with which to gauge their chances of other cancers.
"They have other risk factors, not just that they've had a skin cancer," he said.