Having a high blood platelet count is a strong predictor of cancer and should be urgently investigated to save lives, says a large-scale study.The study, published in the British Journal of General Practice, calls for general physicians to consider a diagnosis of cancer in patients with unexpected raised blood platelet count -- known as thrombocytosis -- to increase early diagnosis which can save lives.The study analysed the data of 40,000 patients and found that more than 11 per cent of men and six per cent of women over the age of 40 with thrombocytosis went on to be diagnosed with cancer within a year.This rose to 18 per cent of men and 10 per cent of women if a second raised platelet count was recorded within six months.In the general population, around one per cent develop cancer in any one year. "We know that early diagnosis is absolutely key in whether people survive cancer. Our research suggests that substantial numbers of people could have their cancer diagnosed up to three months earlier if thrombocytosis prompted investigation for cancer," said lead author Sarah Bailey of the University of Exeter Medical School in Britain."This time could make a vital difference in achieving earlier diagnosis," Bailey added.Lung and colorectal cancer were more commonly diagnosed with thrombocytosis, the study showed.One-third of patients with thrombocytosis and lung or colorectal cancer had no other symptoms that would indicate to their doctor that they had cancer.