Cancer on the breath

Back pain and indigestion are not normally causes for major concern. In rare cases, however, they signal pancreatic cancer, one of the most fatal cancers globally. These vague symptoms mean that by the time patients are referred for scans or endoscopy, around four in five are diagnosed too late for curative treatment. A new breathalyser-style test could change that.

Since 2007, Professor George Hanna and a group of researchers at Imperial College London have been developing a diagnostic test that detects volatile organic compounds (VOCs) in the breath. Cancer triggers the production of unique patterns of VOCs in the human body, which can be identified even at early stages of the disease. “We know that dogs can smell cancer – even some relatives of cancer patients can smell there is something unusual,” says Professor Hanna, recounting his inspiration for the trial.

The team’s end goal is a “pan-cancer” breath test, capable of detecting oesophageal, gastric, liver, pancreatic, and colorectal cancer.

The procedure is simple. Patients breathe into a bag attached to a small collection device at their local doctors’ surgery, which pumps compounds from the breath into a solvent inside a stainless-steel tube. After being analysed in a laboratory, a process which takes around half an hour, the tubes can be sterilised and reused.

VAPOR 1, a two-year study analysing breath samples of 700 patients with confirmed pancreatic cancer, reported promising diagnostic accuracy. With £1.1 million of new funding, Hanna’s team is advancing onto a larger national trial, VAPOR 2, involving over 6,000 patients with suspected cancer. If successful, the technology could be deployed across the UK’s National Health Service (NHS) within the next five years. The team will run a concurrent trial in India and is in talks to do the same in the US. 

The economic case is part of the appeal. Early estimates suggest that breath testing could save the NHS £155 million each year by reducing reliance on scans and invasive procedures like endoscopies. More advanced studies to quantify the lives and costs that could be saved are ongoing.

Breath tests offer an early diagnostic alternative by focusing on the body’s metabolic reactions. 

Diagnostic cancer testing is a crowded field. Several groups are working on cancer-detecting blood tests, which target tumour DNA circulating the blood stream. Pancreatic cancer sheds little detectable DNA in its early stages, so breath tests could offer an alternative for early diagnosis by focusing on the body’s metabolic reaction instead.

In late 2025, an expert committee advised the NHS against the universal use of a blood test for prostate cancer, citing overdiagnosis of harmless tumours and resulting unnecessary, risky treatment. Breath testing faces a similar risk of false positives, but Professor Hanna nevertheless sees it as a potential triage tool for suspected cancer patients. He is awaiting the results of validation studies.

Blood testing is a complement – not a competitor – to breath testing, Hanna says. He believes a comprehensive suite of tests is needed to detect cancer earlier and more accurately whilst reducing the need for invasive procedures and expensive scans. “In life,” Hanna reflects, “you succeed by collaboration rather than by competition.”