Researchers have found it may be possible to look for "markers" of cancer cells in routine blood samples and use them to better gauge whether early breast cancer will progress.
The blood test looks for circulating tumour cells (CTCs) in patients with breast cancer. While conclusive data about their relevance has been established for breast cancer that has spread, the CTC test has not been proven to be predictive in early breast cancer, the researchers noted.
Preventing the spread
It's hoped the CTC blood test will function as a real-time biopsy, providing an early alert system to identify patients who aren't responding to treatment, said lead researcher Dr Brigitte Rack, senior physician in the department of gynaecology and obstetrics at Ludwig-Maximilians University, in Munich.
Besides noting the presence and number of tumour cells in the blood, researchers may be able to study their genetic characteristics, or phenotype, to personalise treatment, Rack said.
"Our data confirms the prognostic relevance of CTCs within a large prospective trial," said Rack. "CTCs could help identify patients with increased risk for relapse who might benefit from additional systemic treatment approaches."
The idea is to prevent spread of the disease "by destroying these minimal residuals", she said.
While the CTC test is commercially available now, the researchers don't recommend its use yet to influence treatment decisions in early breast cancer. "CTC detection in early disease should be limited to patients within clinical trials," said Rack.
Predicting the spread
For the study, published in the Journal of the National Cancer Institute, the researchers analysed the blood of over 2 000 patients after surgery but before chemotherapy, and about 1 500 patients after chemo.
The investigators identified four groups of patients: those who had CTCs before and after treatment; those with no CTCs before or after treatment; those who had CTCs before treatment but not afterwards; and those who only had CTCs after treatment. All participants were followed for about three years.
The results suggest these tumour cells may help predict the spread of breast cancer both before and after chemotherapy, the researchers concluded.
Patients with CTCs in their blood before and after treatment had the shortest disease-free survival time compared to the other three groups.
In general, the chance of being disease-free three years after surgery was lower for those with CTCs than for those without, the results indicated.
Among those who died during the follow-up period, about 41% had CTCs in their blood. Of those who survived, only about 21% had CTCs.
Data not yet definitive
While the study is promising, it's too soon to know what to do when a patient has a positive CTC, said Dr Arnold Schwartz, author of an editorial accompanying the study. "Should we change chemo, or give more chemo? Clearly we can tell the patient that this is something we need to follow. But the data is not definitive yet," he said.
The test might be informative in terms of prognosis and management, but the data isn't entirely clear, Schwartz wrote. "Many patients with [cancer that has spread] do not demonstrate expected CTCs, and several case patients with CTC positivity did not have recurrence within the three-year follow-up," he noted.
Schwartz, a professor of pathology and surgery at George Washington University in Washington, DC, said he believes that as CTC technology improves, physicians will better understand the circulating cells' unique characteristics, such as their sensitivity to chemotherapy and the way they reproduce and disseminate.
For now, he is cautious about the implications of the study. "Science is a very plodding march. Everyone will say this is an important step in the understanding of how tumours spread and biomarkers of breast cancer," he said. "But what are you going to do with the data? Can a person with a negative CTC be relaxed? Life is a risk."