Table 1.

The pros and the cons of anaplastic lymphoma kinase (ALK) gene analysis with a liquid biopsy in non small cell lung cancer patients.

Pros
	Non-invasive method
	Easily repeatable
	Monitoring for early detection of mutation onset in the ALK gene
	Alternative approach to a tissue biopsy when:   Presence of a non-biopsiable tumor site   Patient is fragile   Presence of a weak percentage of tumor cells   Poor quality of extracted RNA
Cons
	ALK status assessment in circulating tumor cells is not available routinely
	The quality of the results is strongly related to some pre analytical parameters:   Volume of blood sample   Tubes used for blood collection   Delay for transfer to the laboratory   Centrifugation procedure   Temperature of plasma/platelets storage
	Large variability of amount of CTCs and free tumor RNA and platelets associated tumor RNA according to the patient