There is some good news for people who suffer from cancer.
In a report published today, the respected British Medical Journal says dogs can smell cancer.
The Journal said a comprehensive medical study revealed that dogs can be trained to identify bladder cancer by smelling urine.
The study comes 15 years after a doctor first alerted the medical world in the other respected British medical publication Lancet about a dog whose persistent sniffing of a mole on its owner's leg led the lady to take a medical test. The mole was found to be cancerous.
This led doctors to suspect that cancerous tissues could have a smell that alerted dogs.
Doctors at the Amersham hospital in Buckinghamshire conducted a detailed study where six dogs were trained to smell the urine of people with bladder cancer and those who were cancer-free.
Dr Carolyn Willis, the lead researcher on the project, said the dogs had a success rate of 41 percent.
What encouraged the doctors greatly was the fact that the dogs actually smelt out a man who had been thought to be cancer-free.
Their persistent sniffing led the doctors to investigate the man's condition. A probe revealed a tumour in the man's kidney.
'Dogs have these fantastic olfactory abilities,' Dr Willis said. 'They are recognising a signature smell of cancer which is very difficult to pick up by any chemical methods. They are not just detecting a single chemical. They were having to pick out smells for bladder cancer amongst the hundreds in urine and that's no mean feat.'
Spaniels performed best, the dogs' trainer Claire Guest added, though the six dogs involved in the study came from different breeds and were of varying ages.
The doctors now hope to discover whether the dogs can detect other cancers.