Cancer cells circulating in the bloodstream, known as circulating tumour cells (CTCs), have been shown to have potential as a prognostic factor for metastatic breast cancer.

A group of scientists from the University of Munich, Germany have shown that they can detect CTCs before and after chemotherapy treatment and hence may be able to identify patients likely to have a recurrence.

Dr. Julia Jücstock, speaking at the European Cancer Conference in Barcelona, suggested that the results could help improve the design of trials of chemotherapy in breast cancer, individualising treatment as well as reducing costs to health services.

The team analysed blood samples from 1767 node-positive and high-risk node-negative breast cancer patients before the start of the treatment and compared the results to those obtained from 852 of the same patients after completion of chemotherapy. "We found that 10% of patients whose blood was sampled before the start of treatment had more than one CTC, and 5% of these patients had more than two CTCs in approximately 20 ml of blood," said Dr. Jückstock. There was found to be a correlation between CTCs and lymph node metastases but not with other prognostic factors such as tumour size, grading, and hormonal or Her-2 status.

A control was run of 24 healthy individuals, with none showing more than one CTC throughout the trial. Among the 852 patients whose blood was analysed post-treatment, 11% were CTC positive before the start of treatment, while 7% had more than one CTC after completion of chemotherapy.

Of those patients who were initially CTC positive, 10% remained so and 90% had a negative CTC test after chemotherapy. Of those initially CTC negative, 93% remained negative, whereas 7% had a positive CTC result.

Screening for CTCs holds the advantage of being easily repeatable as necessary, unlike many other predictive factors. Dr Jücstock referred to the procedure as "simple", "viable in most large hospitals", and "much more patient friendly than bone marrow sampling".

"We think that the persistence of CTCs after chemotherapy treatment is likely to be predictive of the likelihood of recurrence of cancer in these patients," said Dr. Jückstock, "and we will be working to analyse the prognostic value of our findings. If this proves to be the case, it will open the door to a simple way of monitoring the likely outcome of chemotherapy, as well as enabling us to target treatments more precisely"

"The technology hasn't been proved yet but is extremely exciting" added Professor John Smyth, president of the Federation of European Cancer Societies (FECS).