John McCain has a 6 per cent chance of dying of skin cancer every year, according to a medical report that will intensify scrutiny of the Republican presidential nominee’s health.

The 72-year-old Arizona Senator has a history of melanoma, the most deadly form of skin cancer, and a new analysis of his health records has concluded that there is an appreciable chance of a fatal tumour returning.

John Alam, a cancer specialist based in Cambridge, Massachusetts, has used details of Senator McCain’s last brush with cancer in 2000 to calculate his prognosis.

Using the Schuchter model, the standard tool for predicting long-term mortality after skin cancer, Dr Alam found that Senator McCain’s annual risk of death would be 12 per cent for each of the next two years, and would remain similar for several years ahead.

The Schuchter model, however, is based on patient data collected before the development of a new test called the sentinel lymph node biopsy, which indicates whether a cancer has spread.

Senator McCain has taken this test, and it showed that his cancer had not spread. This gives him a better prognosis than would otherwise be the case, roughly halving his annual risk of death from skin cancer.

“If we assume that this trend is maintained long-term, McCain’s mortality risk due to melanoma is better but not eliminated, remaining at 6 per cent per year,” Dr Alam said. The background risk of dying from melanoma is 3.1 per 100,000 people in the UK for men.

The analysis, which is published in a letter to The Lancet medical journal, will raise fresh concern about the health of Senator McCain and his judgment in selecting Sarah Palin as his running-mate.

At 72, he would be the oldest non-incumbent US president to be elected, and as well as war wounds suffered in Vietnam he has had several health scares. He has had four melanomas removed, the most serious in August 2000.

In May he released 1,173 pages of medical records in an attempt to prove that he is sufficiently fit to be president. Experts have used these to reach different conclusions about his current health: a previous analysis by The Washington Post put his annual risk of death from melanoma in low single digits.

Dr Alam’s letter to The Lancet is based on his analysis of the 2000 melanoma. “McCain’s physicians provided a brief summary of his health status in May, 2008,” he wrote. “As a result, using the prognostic model, his predicted 10-year survival at the time of diagnosis was only 24 per cent.”

Dr Alam, an independent consultant to the biotechnology industry and a former research fellow at the Dana Farber Cancer Institute in Boston, declared that he was a registered Democrat who had made financial contributions to Barack Obama’s campaign.

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