Counting the number of lung cancer cells in the blood could be one method of ascertaining how aggressive the disease is and help predict the best treatment to use, according to scientists.
The Cancer Research UK findings looked at the number of circulating tumour cells (CTCs) in blood samples of 101 non small cell lung cancer patients before and after one cycle of chemotherapy.
Lung patients with five or more CTCs had significantly worse survival chances, according to the findings which have been published in the Journal of Clinical Oncology.
Radiotherapy and chemotherapy are able to slow the growth of lung cancer but in most patients the cancer returns and is more resistant to treatment, but there are no tests available that provide early warning about resistance.
Counting CTCs could be a simple way to monitor how well a patient is responding to treatment within a few weeks of starting it.
Being able to detect when CTC numbers are rising could give doctors the option to move patients on to new treatments earlier.
Dr Fiona Blackhall, joint author and lung cancer clinician at the Christie hospital in Manchester, said: "Our research shows a new way to monitor how a patient's lung cancer is responding to treatment and determine how aggressive it is. We now need to test our findings in more patients but, if our results are confirmed, there is now the potential to tailor treatments to individual patients and find new ways to treat the disease."
Around 50% of patients do not respond to existing treatment but may be exposed to the side-effects that accompany some of these treatments.