A simple blood test can save lives by helping doctors swiftly diagnose whether a patient with early breast cancer faces high risk of death or relapse after treatment, specialists said Wednesday.
Tumour cells in a blood sample, when taken at an early stage of the disease, are an accurate predictor of a patient's survival chances, the team said in the journal The Lancet Oncology.
The findings could help identify early on which patients might benefit from additional treatment like chemotherapy.
"The presence of one or more circulating tumour cells (CTCs, in the blood) predicted early recurrence and decreased overall survival," said the researchers from the University of Texas' MD Anderson Cancer Center.
The more CTCs they found, the higher the risk of death.
CTC blood tests are not currently used to analyse a patient's prognosis or prescribe treatment, as cancer tumours are generally thought to spread through the lymphatic system rather than the bloodstream.
The team conducted tests on 302 patients treated at the centre between February 2005 and December 2010.
The subjects were at an early phase of breast cancer -- before it spread to other parts of the body -- and had not received chemotherapy.
The team found CTCs in a quarter of the group.
Of those with tumour cells in their blood, one in seven relapsed after treatment and one in 10 died during the test period.
By contrast, patients whose blood tests yielded no CTCs had a relapse rate of three percent and a death rate of two percent.
"For patients with a higher concentration of CTCs, the correlation with survival and progression rates was even more dramatic, with 31 percent of these patients dying or relapsing," said a press release accompanying the study.
Previous research showed similar results in patients with breast cancer that had already metastasised, or spread. The new study claims to show that "advanced disease is not necessary for cancer cells to spread (via the blood) and compromise survival."
Others urged caution, saying the research was in its infancy and urging larger clinical studies.
"It's great work and very well conducted. We just don't know how to act on the study yet, ie what to do differently with our patients," Justin Stebbing of the Department of Surgery and Cancer at London's Imperial College told AFP.
In particular, it was not clear whether the CTC count must be measured before, during or after surgery to remove the cancerous growth.
Nor was it clear what effect chemotherapy would have on the CTC markers.