ABSTRACT
Recently, circulating tumor cells (CTCs) of cancer patients have been analyzed as a biomarker of disease progression and as a new prognostic tool.We conducted a pilot study to determine whether CTCs present before and after chemotherapy or peptide vaccination predicted outcome in patients with metastatic breast cancer (MBC). CTCs were isolated from the peripheral blood of MBC patients and evaluated using the CellSearch®System (Janssen Diagnostics). The expression of the HLA classâ molecule in the CTCs was analyzed simultaneously by using a flow cytometric system. A CTC-positive test result was defined as five or more CTCs/7.5 mL blood. Nine patients (median [range] age, 64.2 years [44-80 years]) were included. Four (57.1%) of 7 MBC patients with Luminal A subtype tested positive for CTC.Of 6 MBC patients, 5 (83.3%) had a decreased mean number of CTCs, from 35.8/7.5 to 0.4/7.5 mL, after 3 courses of systemic chemotherapy. Furthermore, CTC-HLA class â expression level was decreased in 2 (66.7%) of 3 patients after cytotoxic chemotherapy but increased in 4 (80.0%) of 5 patients after 6 vaccinations with tumor-specific peptide vaccines. The number of CTCs and CTC-HLA class â expression level in the patients with MBC changed after the treatment with systemic chemotherapy or peptide-vaccine therapy.