A fluorescent "throat spray" which pinpoints abnormal cells could help doctors detect early oesophagus cancer, research has revealed.
The technique involves spraying a fluorescent dye into the oesophagus that attaches to normal, healthy cells. The dye cannot stick to cancer cells or those turning malignant.
Abnormal cells stand out from healthy cells that glow green under light of a specific wave length. They can then be seen with an endoscope - a flexible optical device - passed down the oesophagus.
Affected areas can be treated with radiofrequency ablation, a minimally invasive method of killing cancer cells using electrical current.
The disease, which killed Morse star John Thaw, can easily be missed or wrongly diagnosed in its early stages. Often patients are given unnecessary invasive treatment, including removal of the oesophagus - the "food pipe" which connects the throat to the stomach.
Dr Rebecca Fitzgerald, from Cambridge's Medical Research Council cancer unit led the study published in the journal Nature Medicine.
She said current methods to screen for oesophageal cancer were "controversial" as they are "costly, uncomfortable for the patient and not completely accurate".
"Our technique highlights the exact position of a developing oesophageal cancer, and how advanced it is, giving a more accurate picture," she explained.
"This could spare patients radical surgery to remove the oesophagus that can result in having to eat much smaller more regular meals and worse acid-reflux."
After pilot studies on large numbers of tissue samples, the spray was tested on four patients in the process of having early cancer removed.
In two cases, the spray revealed hidden pre-cancerous areas that had evaded detection by conventional imaging.
Another patient whose entire oesophagus had been removed was shown to have undergone unnecessary treatment as the cancer only affected a small area and could have been treated less drastically.
Co-author Professor Kevin Brindle, from Cancer Research UK's Cambridge research institute, said: "The benefit of using this dye is that it is specific, relatively cheap and is found in our normal diets so unlikely to cause any unwanted effects at the levels we use.
"We now need to test our technique in newly diagnosed patients, but it has great potential to be used with current imaging techniques to help improve treatment for oesophageal cancer."
Oesophageal cancer is the ninth most common cancer in the UK.
Each year around 8,000 people in the UK are diagnosed with oesophageal cancer and rates of the disease in men have risen by more half in a generation.
Risk factors for the disease include alcohol use and smoking.
Because oesophageal cancer is often not identified before it has spread, it is one of the deadliest cancers.
Dr Julie Sharp, senior science information manager at Cancer Research UK, said the cancer is "one of the most difficult cancers to detect and treat", with only 8% of people with the disease surviving at least five years.
"We urgently need new ways to detect the cancer earlier, and this dye offers a great opportunity to treat the cancer more promptly and more successfully, potentially saving many lives a year," she added.