Circulating tumor cells count as a predictor of survival in lung cancer

The presence of circulating tumor cells (CTCs) in the peripheral blood of cancer patients was first described in the second half of the 19th century, but research interest in their potential clinical utility has intensified and greatly expanded only in recent years. Herein, we summarize and critically discuss current knowledge on CTC count as a predictor of survival in lung cancer, and comment on the existing challenges and future perspectives in this field. The majority of data published to date, including the results of almost all large cohorts, are strongly supportive of the value of CTC enumeration as a predictor of survival, mainly in advanced/metastatic non-small and small cell lung cancer (NSCLC and SCLC, respectively). Nonetheless, additional research is warranted to establish the prognostic relevance of CTC count in other clinical settings, mainly encompassing earlier-stage disease as well as specific molecular subtypes of NSCLC (e.g. EGFR mutation-positive or ALK-positive cases).