New research has found that early signs that a patient’s lung cancer may spread and become untreatable can be picked up in samples of their blood and tumour.

The three studies, published in Nature Medicine, are all part of Cancer Research UK’s £14million TRACERx project, which aims to understand how lung cancer cells change over time and become resistant to treatment.

The new findings may provide clues as to which patients could be safely treated with milder therapies, such as surgery alone, and which may need additional treatments including chemotherapy. They could also help researchers develop new ways to treat the more aggressive forms of lung cancer.

TRACERx, which involves over 750 patients from 13 UK hospitals, is examining how lung cancer cells evolve and spread via the blood, as well as how the body’s immune system responds.

In these particular studies, just before surgery to remove lung tumours, the team took samples of patients’ blood from veins running away from their affected lungs. They then searched the blood samples for cancer cells that had escaped from the tumour site and looked at the number and types of these cells.

Professor Caroline Dive from the Cancer Research UK Manchester Institute said that they “monitored the patients for up to four years and found that those with the most tumour cells in their blood samples taken from the site of the tumour were also the ones most likely to suffer a recurrence.”

She continued, “By looking at an individual patient who unfortunately had their cancer come back and spread ten months after surgery, we were able to identify the possible cause. We traced the origin of the secondary tumour to particular cells that were escaping into the blood from the primary tumour at the time of surgery.”

Around 47,000 people are diagnosed with lung cancer in the UK each year and fewer than one in five survives for five years or more. Researchers believe a key reason why so few people survive lung cancer is that the tumour cells rapidly evolve, developing resistance to current treatments and evading the body’s immune system.