循環腫瘤細胞的檢測法及臨床應用

Detection Methods and Clinical Utility of Circulation Tumor Cells

循環腫瘤細胞是非侵入性癌症檢驗及治療追蹤的良好標記，可藉由監控循環腫瘤細胞的量來達到監控腫瘤進展及療效之目的，因可取代腫瘤組織切片，因此又稱為液體切片(liquid biopsy)。循環腫瘤細胞的分離，需經過三個主要的步驟：採血、富集(enrichment)及檢測(detection)，為有效分離出微量的循環腫瘤細胞，臨床上常以細胞表面的抗原分子及細胞物理特性（如大小、密度），將循環腫瘤細胞從血液中分離出來，富集的方法例如：微濾膜分離法、微流體分離法、免疫吸附法等，這些方法常使用表皮細胞粘著分子（簡稱EpCAM）當作循環腫瘤細胞的特定標記，然而EpCAM有時會消失，且並非所有種類的腫瘤細胞表面都有EpCAM，因此欲使用循環腫瘤細胞做為臨床的應用，目前仍充滿了挑戰，這些挑戰包括：需考量檢測方法的敏感度、欲檢測之腫瘤細胞種類，此外有些腫瘤並不易釋放細胞至血液中，因此循環腫瘤細胞與癌症治療之關聯性還正逐步建立中。雖然如此，循環腫瘤細胞仍是一種可提供給臨床快速、便利、較貼近腫瘤實際狀況之重要訊息的檢測方式。

Circulation Tumor Cell (CTC) is a good biomarkers for noninvasive cancer diagnosis and treatment effectiveness. Measuring the number of CTCs can be used for monitoring disease progression and the evolution of CTCs after treatment and is so called ＂liquid biopsy＂. There are three major procedures: sample collection, enrichment and detection. Several technologies have been developed to separate CTCs from other blood cells, most of them are based on the surface antigens or physical properties of CTC, such as microfiltration, microfluidic, immunoaffinity. Epithelial cell adhesion molecule (EpCAM) is the most popular used marker, but numerous studies have demonstrated that EpCAM may be disappear on cell surface, and EpCAM is not a universal marker for all kinds of tumor cells. Lots of challenges hamper the clinical utility of CTCs, include the sensitivity of detection methods, types of tumor and selected biomarkers, and the correlation of CTC and treatment. However, detection of CTCs is a rapid, convenient method for tumor information.