Utility of measuring circulating tumor cell counts to assess the efficacy of treatment for carcinomas of unknown primary origin

Background/Aim: Carcinomas of unknown primary origin (CUPs) account for 3%-5% of all malignancies. The majority of CUPs have unfavorable prognosis and are chemoresistant. Predictive biomarkers should be established to improve therapeutic outcomes. Metastatic ability of CUPs may be related to the existence of circulating tumor cells (CTCs). Patients and Methods: Ten patients diagnosed with CUP visiting the Akita University Hospital participated in this study. CTCs were calculated by the CellSearch system. Results: The present observational study indicates that CTCs were detected in 50% of CUPs, and in 80% chemotherapeutically-naïve cases. Furthermore, decrease in CTC count between the pre-treatment and posttreatment phases were observed in chemosensitive cases. Conclusion: Rapid assessment of the efficacy of chemotherapy by CTC count may become a useful predictive biomarker of CUPs.