EORTC Treat CTC study was presented today during the plenary session at the European Breast Cancer Conference in Barcelona, Spain. This Phase II study assessed whether trastuzumab decreases the detection rate of Circulating Tumour Cells (CTCs) compared to observation in women with HER2 non-amplified, non-metastatic breast cancer.
Circulating tumour cells are cells that detach from the primary tumour and move into the vascular or lymphatic system. These cells then attach themselves to other organs forming distant metastases and eventually causing a number of cancer related deaths. CTCs can be considered as “liquid biopsies” and can help to evaluate the disease status of a patient. However, there are differing results about the effectiveness of different treatments to reduce CTCs.
The EORTC 90091-10093 Treat CTC trial showed that, out of 1317 patients from 70 hospitals in five European countries, 95 patients had detectable CTC, 63 patients were randomly assigned to trastuzumab or observation. Fifty-eight patients were evaluable for the primary endpoint of CTC detection at week 18. It was found that, in this week, nine patients (five in the trastuzumab arm and four in the observation arm), still exhibited CTCs in their blood sample. Following a review by the Independent Data Monitoring Committee, further accrual to the study was stopped, as the trial could not meet its primary endpoint, it was viewed that even with continuous accrual this endpoint would never be met. The first year invasive disease free survival was 93.8% in the observational arm versus 84.8% in the trastuzumab arm. No grade 2-4 cardiac events were observed in the trastuzumab arm.
Leading investigator, Dr Michail Ignatiadis, Medical Oncologist at Jules Bordet Institute (IJB) and Assistant Professor at the Université Libre de Bruxelles, Brussels, Belgium, concluded that Trastuzumab does not decrease the detection rate of Circulating Tumor Cells in HER2 non-amplified, non-metastatic breast cancer. He said, “Although clearly a negative trial, the ‘Treat CTC’ introduced, for the first time, the use of liquid biopsy as a tool for precision medicine in early breast cancer.”