Non-Small Cell Lung Cancer (NSCLC)

Molecular testing is an integral component of the pathological assessment of NSCLC. Although the diagnosis and histological type are established primarily by morphology and immunohistochemistry, clinically relevant oncogenic alterations cannot be predicted reliably from tumour morphology or patient characteristics alone.

The principal clinical value of molecular testing of tumour tissue is predictive: identification of an actionable alteration can determine eligibility for targeted therapy and directly influence the selection and sequencing of systemic treatment. Molecular findings may also support tumour classification in selected cases. Some molecular alterations are associated with clinical or prognostic features, although their independent prognostic significance is context-dependent and generally secondary to their predictive value. At disease progression, testing of a new tissue specimen or circulating tumour DNA may identify acquired resistance mechanisms and help guide subsequent treatment.

Broad molecular testing is particularly important in advanced or metastatic non-squamous NSCLC and should not be restricted by age, sex, smoking history or ethnicity. Testing may also be appropriate in selected tumours diagnosed as squamous NSCLC, especially in small specimens in which an adenocarcinoma component cannot be excluded. Biomarker testing is also relevant in earlier disease stages. In defined resectable or perioperative settings, the identification of EGFR mutations, ALK rearrangements and, according to the current NCCN pathway, RET fusions may influence treatment planning.

Validated multiplex testing is preferred over sequential single-gene analyses whenever possible because diagnostic biopsy material is often limited and several uncommon but therapeutically relevant alterations must be assessed in parallel.

Recommended predictive biomarkers

For advanced NSCLC, molecular testing should cover the major currently established predictive biomarkers and potentially actionable alteration classes, including:

• EGFR activating mutations
• ALK fusions
• ROS1 fusions
• BRAF (especially p.V600E)
• KRAS (especially p.G12C)
• MET exon 14 skipping alterations (see Panel 00617 – “Solid tumour comprehensive profiling”)
• RET fusions
• NTRK1, NTRK2 and NTRK3 fusions
• ERBB2 (HER2) activating mutations
• NRG1 fusions (see Panel 00617 – )

The exact biomarkers required depend on disease stage, histological context, previous treatment and the current guideline and drug-authorisation status. PD-L1 expression should be assessed separately by validated immunohistochemistry because it contributes to immunotherapy selection but is not a genetic biomarker.

Formalin-fixed, paraffin-embedded tumour tissue is commonly used for molecular testing. Plasma circulating tumour DNA analysis can complement tissue testing when tissue is unavailable or insufficient and may be useful at progression. Because ctDNA shedding varies, a negative plasma result does not exclude a tumour alteration and should be followed by tissue-based testing whenever clinically feasible.

Results must be interpreted in the context of tumour type, disease stage, specimen quality, previous treatment and current clinical guidelines. Treatment decisions should be made by the multidisciplinary treating team. The therapeutic relevance of individual alterations and the applicable drug approvals may change as new evidence becomes available.

Current management and alteration-specific therapy recommendations for patients with NSCLC (including tyrosine kinase inhibitors (TKIs), antibody-drug conjugates and other targeted agents) are provided by the (ESMO oncogene-addicted metastatic non-small-cell lung cancer living guideline, v1.3, February 2026) and by the (NCCN Clinical Practice Guidelines in Oncology: Non-Small Cell Lung Cancer, version 7.2026).

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