Possible link between platelets and cancer risk, though further work needed

A possible link between cancer and the levels of a component of blood, called platelets, should be investigated further, according to a new study.

The study found that patients who had a high blood platelet count, known as thrombocytosis, had a higher risk of cancer.

However experts cautioned that the study didn’t look at using platelet count for diagnosis or screening, and pointed out there are many other reasons for a high platelet count.

The research, from the University of Exeter Medical School, looked at the records of 50,000 patients aged 40 and over who received a blood test for a range of reasons, but where cancer was not suspected.

The researchers found that patients with thrombocytosis were more likely to be diagnosed with cancer within a year than patients with a normal blood platelet count.

Of the patients with thrombocytosis, around 11 in 100 men and 6 in 100 women went on to be diagnosed with cancer within a year. For patients with a normal blood platelet count the figures were around 4 in 100 men and 2 in 100 women.

These figures, published in the British Journal of General Practice, rose to 18 in 100 men and 10 in 100 women if a second high platelet count was recorded within six months.

Thrombocytosis affects around 2 in every 100 people over the age of 40 in the UK.

Dr Jasmine Just, Cancer Research UK’s health information officer, says: “There are lots of reasons why a person’s platelet count might be high, and in most cases it won’t be down to cancer.”

She added that measuring platelet levels in patients who don’t otherwise need a blood test may lead to additional unnecessary tests and anxiety.

“If a patient has a blood test for another reason and a high platelet count is found, then one of the possible diagnoses doctors should consider is cancer,” she added. 

“More research is needed to confirm whether investigating people for cancer just based on a high platelet count would result in earlier diagnosis or save lives.”

Lead author, Dr Sarah Bailey, suggested that if thrombocytosis is considered as an indicator of cancer, around 5,500 patients may be diagnosed up to three months earlier each year.

But Just added that it wasn’t clear from the research what proportion of cancer diagnoses would have gone on to cause problems in a patient’s lifetime, and what proportion might have remained safely undetected and not resulted in symptoms or death.