Non-Small Cell Lung Cancer: Laboratory Testing for Diagnosis and Management
Lung cancer is the second most diagnosed cancer in men and women in the United States and is the leading cause of cancer death.1 Non–small cell lung cancer (NSCLC) accounts for approximately 85% of lung cancers.1
NSCLC is commonly diagnosed at a late stage.2 Treatment focuses on improving survival and minimizing disease-related adverse events.3 Chemotherapy remains an important part of treatment; however, the survival rates for metastatic NSCLC are low.4 First-line, targeted therapies that are based on genetic alterations in the tumor have reduced NSCLC mortality and improved survival.5 Testing to identify gene variants (biomarkers) present in the tumor can identify patients who are mostly likely to benefit from specific treatments.6
Therapeutic advances linked to specific biomarker testing of tumor tissue have been shown to improve the outcomes of patients with NSCLC diagnosed at all disease stages.7 However, an estimated 40% of patients with NSCLC do not receive recommended biomarker testing.8
This article discusses diagnosis of NSCLC and the importance of biomarker testing for determining prognosis and guiding therapy.
NSCLC epidemiology, deaths, and survival rates
The American Cancer Society (ACS) estimates that in 2022 there will be about 237,000 new cases of lung cancer and about 130,000 lung cancer deaths (new cases and deaths are approximately equal between men and women).1 Lung cancer accounts for almost 25% of cancer deaths; more people die each year due to lung cancer than colon, breast, and prostate cancers combined.1 The greatest risk factor for lung cancer is smoking, but other factors can also increase risk (see Sidebar).1,9 Screening (see Sidebar) is recommended only for persons at high risk.10
More than 50% of patients have stage III or IV disease at the time of diagnosis; 40% of cases are diagnosed at stage IV.2 The overall 5-year relative survival rate for patients with NSCLC is 26% (2011-2017).4 However, survival decreases markedly with more advanced-stage disease (Table).
Table. Non–Small Cell Lung Cancer Stage at Diagnosis and 5-Year Relative Survivala
a Relative survival: a method of comparing the survival of people with a specific disease with those who do not have the disease. Relative survival is calculated by dividing the percentage of patients with the disease who are still alive at the end of a time period (in this case 5 years) by the percentage of people in the general population of the same sex and age who are alive at the end of the same time period.
NSCLC symptoms, diagnosis, and subtypes
The most common symptoms of lung cancer include9
- Chronic/worsening cough
- Chest pain
- Weight loss
Diagnosis requires pathologic examination of a lung biopsy specimen to assess histologic type and other tumor characteristics. A biopsy is typically performed if chest computed tomography (CT) identifies a >8 mm solid nodule(s), or part-solid nodules with a solid component ≥6 mm.6
The main histological subtypes of NSCLC are adenocarcinoma (about 78% of NSCLCs) and squamous cell carcinoma (about 18% of NSCLCs), with other rare subtypes comprising about 4% of cases.11 Squamous NSCLC tends to occur at an older age and to be detected at more advanced disease stage, and the median survival is about 30% shorter than for other NSCLC subtypes.12
Most biomarkers with respect to NSCLC are gene variants (eg, mutations, rearrangements, fusions) in tumor cells.6 A notable exception is programmed death-ligand 1 (PD-L1) expressed on tumor cells (discussed below).6 Identification of biomarkers has substantially improved the outcomes of patients with NSCLC because they can indicate increased sensitivity to specific treatments. For example, the 2-year relative survival rate for patients with NSCLC increased from 34% during the period of 2009 through 2010 to 42% from 2015 through 2016.7 One factor that likely contributed to the survival gains was the development of epidermal growth factor receptor tyrosine kinase inhibitors (TKIs) targeted against the most common NSCLC driver variants.13
National Comprehensive Cancer Network (NCCN®) guidelines, as well as those of other professional organizations, recommend testing for specific gene variants in patients with NSCLC.6,14 Relevant genes include ALK, BRAF, EGFR, ERBB2 (HER2), KRAS, METex14, NTRK1/2/3, RET, and ROS1.6
Biomarkers are typically categorized as actionable (a specific treatment exists that can improve outcomes in patients with the biomarker) or emerging (study suggests that treatment based on the biomarker may improve outcomes).6 Testing methods include fluorescence in situ hybridization (FISH), immunohistochemistry (IHC), and next-generation sequencing (NGS).6
Actionable NSCLC biomarkers include
- ALK (anaplastic lymphoma kinase) gene rearrangements6
- ALK encodes a receptor tyrosine kinase and rearrangement results in dysregulation and inappropriate signaling.
- ALK rearrangements are associated with responsiveness to oral ALK TKIs.
- BRAF (B-Raf proto-oncogene) point mutations6
- BRAF is a serine/threonine kinase, and activating variants of BRAF result in unregulated signaling through the mitogen-activated protein kinase/extracellular-signal-regulated kinase (MAP/ERK) pathway.
- The presence of a specific mutation resulting in a change in amino acid position 600 (p.V600E) is associated with responsiveness to combined therapy with oral inhibitors of BRAF and mitogen-activated protein kinase kinase (MEK).
- EGFR (epidermal growth factor receptor) gene mutations6
- EGFR is a receptor tyrosine kinase present on the surface of epithelial cells that is overexpressed in a number of human malignancies.
- The most common EGFR variants (eg, exon 19 deletions) are associated with responsiveness to oral EGFR TKI therapy.
- ERBB2 (erb-B2 receptor tyrosine kinase 2; also known as HER2) variants and/or amplification6 are
- Associated with resistance to EGFR TKIs.
- Targets for fam-trastuzumab deruxtecan-nxki in adults with unresectable or metastatic NSCLC.
- Included as an actionable biomarker in the most recent NCCN guidelines.
- KRAS (KRAS proto-oncogene) point mutations6
- KRAS is a G-protein with intrinsic GTPase activity; activating variants result in unregulated signaling through the MAP/ERK pathway.
- The presence (compared with absence) of a KRAS variant is prognostic of poor survival.
- KRAS variants are associated with reduced responsiveness to EGFR TKI therapy.
- The KRAS p.G12C variant is associated with responsiveness to an oral KRAS G12C inhibitor, which was designed specifically for this variant.
- METex14 (mesenchymal-epithelial transition) exon 14 skipping variants6
- MET is a receptor tyrosine kinase; a variant resulting in loss of exon 14 (METex14) results in dysregulation and inappropriate signaling.
- The presence of METex14 skipping mutation is associated with responsiveness to oral MET TKIs.
- NTRK1/2/3 (neurotrophic tyrosine receptor kinase) gene fusions6
- NTRK1/2/3 are tyrosine receptor kinases, and variants result in dysregulation and inappropriate signaling.
- NTRK1/2/3 gene fusions are associated with responsiveness to oral tropomyosin receptor kinase (TRK) inhibitors.
- T cells express PD-1, a negative regulator that binds to ligands including PD-L1 (CD274) and PD-L2 (CD273). T cell activity is suppressed in the presence of PD-L1.
- PD-L1 can be expressed on tumor cells and inhibits T cell–mediated tumor-cell death.
- “Targeted therapies” or “immunotherapies” that include therapeutic antibodies (eg, pembrolizumab [KEYTRUDA®]) act by blocking the PD-1 and PD-L1 interaction.
- This mode of action, called checkpoint inhibition, improves the antitumor effects of endogenous T cells.
- RET (rearranged during transfection) gene rearrangements6
- RET is a receptor tyrosine kinase, and rearrangement of the RET gene results in dysregulation and inappropriate signaling through the RET kinase domain.
- The presence of a RET rearrangement is associated with responsiveness to oral RET TKIs.
- ROS1 (ROS proto-oncogene 1) gene rearrangements6
- ROS1 is a receptor tyrosine kinase that can be rearranged in NSCLC, resulting in dysregulation and inappropriate signaling through the ROS1 kinase domain.
- The presence of a ROS1 rearrangement is associated with responsiveness to oral ROS1 TKIs.
An emerging NSCLC biomarker is
- METamp (METamplification)6,15
- A MET copy number >10 is considered high-level MET amplification.
- High-level MET amplification is predictive of response to immunotherapy and specific drugs (eg, tepotinib).