High levels of calcium in the blood could provide an early warning of cancer, especially in men, a new study has found.
Hypercalcaemia is the most common metabolic disorder associated with cancer, occurring in 10 to 20 per cent of people with cancer, researchers said.
While its connection to cancer is well known, this study has, for the first time, shown that often it can predate the diagnosis of cancer in primary care.
A simple blood test could identify those with hypercalcaemia, prompting doctors to investigate further.
The research analysed the electronic records of 54,000 patients who had elevated levels of calcium and looked at how many of them went on to receive a cancer diagnosis.
"All previous studies on hypercalcaemia and cancer had been carried out with patients who had already been diagnosed with cancer - hypercalcaemia was seen as a late effect of the cancer," said Dr Fergus Hamilton, from the Centre for Academic Primary Care at the University of Bristol, who led the study.
"We wanted to look at the issue from a different perspective and find out if high calcium levels in blood could be used as an early indicator of cancer and therefore in the diagnosis of cancer," said Hamilton.
Analysis of the data from 54,000 patients found that in men, even mild hypercalcaemia conferred a risk of cancer in one year of 11.5 per cent.
Elevated levels of calcium increased the risk to 28 per cent. In women, the risks were much less, with the corresponding figures being 4.1 per cent and 8.7 per cent.
In men, 81 per cent of the cancer associated with hypercalcaemia was caused by lung, prostate, myeloma, colorectal and other haematological cancers. In women, cancer was much less common, researchers said.
"We were surprised by the gender difference. There are a number of possible explanations for this but we think it might be because women are much more likely to have hyperparathyroidism, another cause of hypercalcaemia. Men rarely get this condition, so their hypercalcaemia is more likely to be due to cancer," Hamilton added.
The study was published in the British Journal of Cancer.
