Addressing a press conference at the European Cancer Conference (ECCO 14) on Monday, Dr. Julia Juckstock said that the results could help improve the design of trials of chemotherapy in breast cancer, and reduce costs to health services.
Led by Dr. Brigitte Rack, the research team analysed the role of CTCs in blood at the first diagnosis of breast cancer and during adjuvant chemotherapy and endocrine treatment.
The researchers analysed blood samples from 1,767 node-positive and high-risk node-negative breast cancer patients before the start of their treatment, and compared the results to those obtained from 852 of the same patients after completion of chemotherapy.
"We found that 10 percemt of patients whose blood was sampled before the start of treatment had more than one CTC, and 5 percent of these patients had more than two CTCs in approximately 20 ml of blood," Dr. Juckstock said.
The scientists found that among the 24 healthy individuals used as controls, none showed more than one CTC.
They said that among the 852 patients whose blood was analysed post-treatment, 11 percent were CTC positive before the start of treatment, while 7 percent had more than one CTC after completion of chemotherapy.
Ten percent of the patients who were initially CTC positive remained so, while 90 percent had a negative CTC test after chemotherapy, say the researchers.
Of those initially CTC negative, 93 percent remained negative, whereas 7 percent had a positive CTC result.
According to the scientists, the benefit of screening for CTCs is that, unlike other predictive factors, including genetic signatures, it can be carried out after the completion of primary therapy, and, if needed, on other occasions during the duration of disease. Other predictive methods can only be used on diagnosis, and only once.
Dr. Juckstock said that the previous work on the detection of CTCs in bone marrow had also been shown to have predictive value.
"It is easier to work with bone marrow, because the volume of CTCs is much higher than in blood in the case of a positive status. However, because bone marrow is not easily accessible it is difficult to use this technique on a large scale. It is very much simpler, and more patient-friendly, to take blood samples for analysis," he said.
"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 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," he added.