Molecular diagnosis in non-small-cell lung cancer: expert opinion on ALK and ROS1 testing

Abstract

The effectiveness of targeted therapies with tyrosine kinase inhibitors in non-small-cell lung cancer (NSCLC) depends on the accurate determination of the genomic status of the tumour. For this reason, molecular analyses to detect genetic rearrangements in some genes (ie, ALK, ROS1, RET and NTRK) have become standard in patients with advanced disease. Since immunohistochemistry is easier to implement and interpret, it is normally used as the screening procedure, while fluorescence in situ hybridisation (FISH) is used to confirm the rearrangement and decide on ambiguous immunostainings. Although FISH is considered the most sensitive method for the detection of ALK and ROS1 rearrangements, the interpretation of results requires detailed guidelines. In this review, we discuss the various technologies available to evaluate ALK and ROS1 genomic rearrangements using these techniques. Other techniques such as real-time PCR and next-generation sequencing have been developed recently to evaluate ALK and ROS1 gene rearrangements, but some limitations prevent their full implementation in the clinical setting. Similarly, liquid biopsies have the potential to change the treatment of patients with advanced lung cancer, but further research is required before this technology can be applied in routine clinical practice. We discuss the technical requirements of laboratories in the light of quality assurance programmes. Finally, we review the recent updates made to the guidelines for the determination of molecular biomarkers in patients with NSCLC.

Keywords: diagnostic techniques and procedures; immunohistochemistry; oncogenes.

Figure 1

Example of a lung adenocarcinoma immunohistochemistry (IHC)-positive for ALK using the Ventana ALK D5F3 antibody (Cdx assay) (×200).

Figure 2

Example of a lung adenocarcinoma positive for ROS1 using the D4D6 antibody (A) and SP384 antibody (B) (×200).

Figure 3

Example of a lung adenocarcinoma positive for ALK (fluorescence in situ hybridisation (FISH) pattern: 1F1O1G) (A) and a lung adenocarcinoma positive for ROS1 with a deletion of the non-rearranged allele (FISH pattern: 1O1G) (B) using break-apart probes (×100).