Expert opinion on NSCLC small specimen biomarker testing - Part 1: Tissue collection and management

Abstract

Biomarker testing is crucial for treatment selection in advanced non-small cell lung cancer (NSCLC). However, the quantity of available tissue often presents a key constraint for patients with advanced disease, where minimally invasive tissue biopsy typically returns small samples. In Part 1 of this two-part series, we summarise evidence-based recommendations relating to small sample processing for patients with NSCLC. Generally, tissue biopsy techniques that deliver the greatest quantity and quality of tissue with the least risk to the patient should be selected. Rapid on-site evaluation can help to ensure sufficient sample quality and quantity. Sample processing should be managed according to biomarker testing requirements, because tissue fixation methodology influences downstream nucleic acid, protein and morphological analyses. Accordingly, 10% neutral buffered formalin is recommended as an appropriate fixative, and the duration of fixation is recommended not to exceed 24-48 h. Tissue sparing techniques, including the 'one biopsy per block' approach and small sample cutting protocols, can help preserve tissue. Cytological material (formalin-fixed paraffin-embedded [FFPE] cytology blocks and non-FFPE samples such as smears and touch preparations) can be an excellent source of nucleic acid, providing either primary or supplementary patient material to complete morphological and molecular diagnoses. Considerations on biomarker testing, reporting and quality assessment are discussed in Part 2.

Keywords: Best practice; Biopsy; Cytological techniques; Histology; Molecular diagnostics; Non-small cell lung carcinoma.

Fig. 1

Cytology cell block cellularity can vary from high (left; suitable for molecular analysis) to low (right; too low for DNA/RNA NGS without mutant allele-specific amplification). DNA deoxyribonucleic acid, NGS next-generation sequencing, x obj microscope objective lens magnification, RNA ribonucleic acid. Images provided by Erik Thunnissen

Fig. 2

Approaches to avoid tissue wastage. ‘One biopsy per block’ approach (a) and tissue-sparing cutting protocols: Diagnose and predict (D + P) protocol, as used by author E. Thunnissen in Amsterdam (b), and an alternative approach, as used by author K. Kerr in Aberdeen (c). ALK anaplastic lymphoma kinase, H&E haematoxylin and eosin, IHC immunohistochemistry, NGS next-generation sequencing, NTRK neurotrophic tyrosine receptor kinase, PD-L1 programmed cell death ligand 1, ROS1 ROS proto-oncogene 1, TTF1 thyroid transcription factor-1