Top eight cancer signs pinpointed
The eight unexplained symptoms most closely linked to cancer have been highlighted by researchers.
The Keele University team also points to the age at which patients should be most concerned by the symptoms, which include blood in urine and anaemia.
The other symptoms are: rectal blood, coughing up blood, breast lump or mass, difficulty swallowing, post-menopausal bleeding and abnormal prostate tests.
Cancer Research UK said unusual changes in a person's health should be checked.
The researchers were looking for symptoms which gave a one in 20 or higher chance of turning out to be cancer.
Although this still represents a relatively low chance of anyone with the symptom having the disease, any suspicion of cancer can mean that the patient is sent for tests more quickly, in order to catch the disease as early as possible.
The figure for each symptom was calculated by combining the results of 25 previous studies.
They found that, if the patient was below the age of 55, there were only two signs which reached the 'one-in-20' threshold.
These were a rectal prostate examination which gave abnormal results, and a breast lump.
After 55, but only in men, there was evidence that difficulty swallowing could be a sign of oesophageal cancer, while blood in the urine was highlighted as a particular concern for men and women aged over 60.
'Not the only signs'
Dr Mark Shapley, who led the research, said: "GPs should audit their management and reflect upon these cases as part of their appraisal to improve quality of care.
"There should be more open public debate on the level of risk that triggers a recommendation for referral by a GP."
Professor Amanda Howe, honorary secretary of the Royal College of General Practitioners, said: "It's useful to see these well-known 'red flag' symptoms and signs validated in primary care research, and reinforces the importance of encouraging patients to discuss worrying symptoms early with their GP."
However, a spokesman for Cancer Research UK said that these were by no means the only potential warning signs for cancer.
"The particular symptoms this study has highlighted are already thought of as important potential signs of cancer, but there are more than 200 different types of cancer, which cause many different symptoms.
"So if you notice an unusual or persistent change in your body it's important to get it checked out. When cancer is diagnosed at an early stage, treatment is often more likely to be successful."