Results from an observational study strongly indicated that circulating tumor cells (CTCs) are an independent prognostic marker in metastatic breast cancer at first-line chemotherapy, and an early predictive marker of clinical benefit after one cycle of chemotherapy. But questions remain about the value of CTCs for guiding treatment decision-making.
SAN ANTONIO-The detection of more than five circulating tumor cells (CTCs) in the peripheral blood of women with metastatic breast cancer appears to signal a rapidly worsening outcome in both progression-free survival and overall survival, according to a study by French researchers. This study is the largest, prospective series to date validating the prognostic value of CTCs for overall survival in patients receiving first-line chemotherapy for metastatic disease, independent from serum tumor markers.
Jean-Yves Pierga, MD, PhD, and colleagues assessed 260 patients for CTC at baseline with CellSearch. CTC counts ranged from 0 to 3,369. They found that 56% of the patients had CTC counts less than five, while 44% had counts of five or greater.
Baseline CTC counts and changes in CTC count after one treatment cycle were significantly associated with progression-free and overall survival. About 90% of patients who had no CTCs at baseline were alive at two years compared with about 30% of patients with more than five CTCs (P < .0001).
Changes in CTCs during treatment differed according to the treatment received, with anti-HER2 targeted agents having the greatest impact. Of the 60 patients with more than five CTCs who were treated with chemotherapy plus bevacizumab (Avastin), 36% still had more than five CTCs after one treatment cycle and 23% after two cycles. Of the 15 patients with more than five CTCs treated with chemotherapy and HER2-positive targeted agents, 17% had more than five CTCs after one cycle of treatment and 0% after two cycles. But among the 39 patients with more than five CTCs baseline treated with chemotherapy alone, 47% still had more than five CTCs after one treatment cycle and 38% after two cycles. ( SABCS 2010 abstract S6-6).
“Circulating tumor cells add an independent prognostic marker in metastatic breast cancer at first-line chemotherapy, and an early predictive marker of clinical benefit after one cycle of chemotherapy,” said Dr. Pierga, professor of the medical oncology department, Institut Curie and Universit Paris Descartes.
But whether CTC information will actually change treatment options is unknown, commented Aman Buzdar, MD, professor of medicine at Houston’s M.D. Anderson Cancer Center.
“I have never ordered a CTC test,” Dr. Buzdar said. “I don’t know that having the information on circulating tumor cells is going to change how we treat our patients. We [currently] treat women with breast cancer based on their hormone receptor status and I am not sure that another test is going to change that significantly.”
Dr. Pierga pointed out that this was an observational study and not designed to manage treatment decisions. Trials in the U.S. and Europe are being developed to determine if CTC levels can translate into personalized treatment options.