Recurring urine infections could mask the symptoms of bladder or kidney cancer, researchers have warned.
Doctors may assume a patient is suffering yet another urinary tract infection (UTI) rather than investigating for potential cancer, they said.
A study presented at Cancer Research UK’s early diagnosis conference in Birmingham examined data from 24 studies of more than 100,000 people in eight high-income countries.
It found that up to two thirds of people with blood in their urine – a UTI symptom and a possible sign of cancer – had no further examination in the six months after their first visit to a doctor.
Researchers found that repeated UTIs were associated with a “diagnostic delay” in detecting cancer, and women were more likely to experience this diagnostic delay than men.
Dr Yin Zhou, lead author from the University of Cambridge, said: “Detecting cancer early is vital for giving patients the best treatment options and improving survival.
“This research is an important step towards improving our understanding of why some people are diagnosed later than others.
“Although UTIs are the second most common condition that GPs are prescribing antibiotics for, in some people, symptoms of a UTI may be masking symptoms of bladder or kidney cancer.
“Only a small number of patients with persistent symptoms and recurring UTIs will go on to develop cancer, but it’s important that we don’t miss them.
“The next step will be to find a way to detect these patients earlier.”
The study suggests that patients with ongoing symptoms could be flagged up electronically on a GP system.
More than 10,500 people are diagnosed with kidney cancer each year in England, while about 8,500 people are diagnosed with bladder cancer.
Of these, about 3,400 are diagnosed with late-stage kidney cancer and 1,800 with late-stage bladder cancer, which lowers the chance of survival.
The NHS website says urinary infections, which affect more women than men, can often be treated with a long course of antibiotics if they keep coming back.
Sara Hiom, director of early diagnosis at Cancer Research UK, said: “Early stage cancers may not always display obvious symptoms, but this research highlights the importance of tracking persistent symptoms and ensuring ongoing problems are not ignored.
“We continue to use the latest evidence to find new ways to support GPs and practices to ensure all patients receive an accurate diagnosis as swiftly as possible – this can make all the difference to their experience and outcome.”
Dr Richard Roope, Cancer Research UK’s GP expert, said: “GPs see many patients with symptoms suggestive of a urinary infection – thankfully the vast majority will never go on to develop kidney or bladder cancer.
“But this research shines a light on the importance of taking a step back to consider what might be causing any recurrence of symptoms, rather than assuming the diagnosis is the same as it has been before.
“There’s no easy way to know which patients need to be referred or seen again.
“All GPs want the best for their patients so research like this, highlighting where improvements need to be made, such as arranging a review, is very useful.”