Circulating tumor cells as a liquid biopsy in small cell lung cancer, a future editorial

CTCs are shed tumor cells that have entered the bloodstream and are able to survive in the blood environment often by endothelial mesenchymal transition (EMT) (1-4). It is thought that CTCs mirror tumor heterogeneity of both the primary tumor and metastases, making them an excellent candidate that reflects the behavior of cancer. CTCs may replace invasive biopsies of the original tumor as a diagnostic tool, lowering the diagnostic burden placed on patients. Follow-up of number of CTCs will give physicians the opportunity to monitor therapy efficacy and observe relapses in time. A major prerequisite is that enough CTCs are being detected; in small cell lung cancer (SCLC) a variable amount of about 20 to 20,000 CTCs are found in 7.5 mL blood.