Test availability

Quest Diagnostics offers many laboratory tests related to the diagnosis, prognosis, treatment, and recurrence of NSCLC (Table 1).

Table 1. Tests Available for Diagnosis and Management of Non–Small Cell Lung Cancer

Test selection and interpretation

Diagnosis and prognosis

Diagnosis of NSCLC requires pathologic examination of the biopsy specimen to assess histologic type and other tumor characteristics. Immunohistochemical studies can assist in differential diagnosis when tumor type or lineage is uncertain.

Pathologic examination

Pathologic examination is used to determine extent of the tumor invasion and its surgical margins, with tumor staging being the foundation of NSCLC prognostic assessment. The TNM (tumor, node, metastasis) system provides standardized scores that describe these anatomic features of lung cancer and indicate the extent of cancer progression.4

Quest offers histopathology testing with interpretation by a pathologist. For NSCLC, tests include gross and microscopic tissue examination (test codes 3541[X] and 3542) and microscopic examination of pleural fluid and fine-needle aspirate specimens (test code 10676). Additional laboratory tests to assist in the diagnosis of NSCLC may be ordered at additional charge by the histopathologist.

Immunohistochemical staining

In addition to staging, histological classification of NSCLC by subtype also has prognostic implications. IHC staining with appropriate markers (see tests available in Table 1) helps identify subtypes as well as differentiate primary lung carcinoma from metastatic carcinoma or primary pleural mesothelioma (Table 2).2,5,6

Table 2. Typical Immunostaining Results in Differential Diagnosis of Non–Small Cell Lung Cancer

Therapy selection

In addition to diagnosis of NSCLC, pathologic examination has implications for therapy selection guided by molecular testing for sensitive and resistant oncogenic driver variants. These variants are most often detected in tumor tissue but can also be detected in blood through circulating tumor DNA (ctDNA). For NSCLC lacking known actionable variants, targeted immunotherapies based on immunohistochemistry may be appropriate. In addition, measurement of biomarkers in plasma can provide information on treatment success, prognosis, or both.

The role of laboratory testing in therapy selection in NSCLC is discussed in the following sections.

Variant profiling

Targeted therapies based on gene-variant profiling for NSCLC are evolving rapidly. Guideline-driven variant profiling can be used to predict sensitivity, or resistance, to a specific therapy.

The College of American Pathologists, the International Association for the Study of Lung Cancer, and the Association for Molecular Pathology recommend testing for EGFR, ROS1, and ALK variants in all advanced adenocarcinoma specimens.7 Additionally, BRAF, MET, RET, ERBB2, and KRAS testing is recommended as part of panels used for initial testing, or if specimens are negative in initial tests for EGFR, ROS1, and ALK variants.7 The American Society of Clinical Oncology endorsed these recommendations with an update of BRAF testing being used as a stand-alone test for all patients with advanced lung adenocarcinoma.8

National Comprehensive Cancer Network (NCCN®) guidance reflects more recent approvals of the targeted therapies by the US Food and Drug Administration (FDA). NCCN recommends that all metastatic nonsquamous NSCLC should be tested for variants in EGFR, ALK, ROS1, BRAF, MET exon 14 (ex14), RET, KRAS, ERBB2 (HER-2),and NTRK (Table 3).2,9–13 NCCN also recommends broad molecular testing for rarer genetic variants (eg, MET amplification) that may have effective therapeutic options.2 NCCN recommends that the same molecular tests be considered for metastatic squamous cell carcinomas.2 Clinicopathologic features (eg, smoking status, ethnicity, tumor histology) associated with certain variants should not be used to direct molecular testing.2 Quest offers testing for these variants (Table 3).

Table 3. Molecular Markers That Guide Therapies for Advanced or Metastatic Non–Small Cell Lung Cancer

Other variants

Quest offers testing for other variants as part of large NGS panels for solid tumors spanning either 49 genes (test code 93234) or 522 genes and the TERT promotor (test code 93233). In these panels, common downstream acceptor genes are also sequenced from RNA to detect potential fusions and splice variants (Table 1 and Appendix). Reports from variant panel testing include the clinical significance, prognosis, and predicted response to therapy for the variant. The variants are classified into 4 tiers based on the strength of the current evidence for their clinical significance (Table 4).14 Some variants are detected only within targeted regions of the selected genes but not in the promoter and intronic variant regions (except for the TERT promoter, fusions, and splice site variants).

Table 4. Variant Classification Tiers

a Tier 4 variants are not reported.

Circulating tumor DNA (ctDNA)

Blood plasma sampling of circulating tumor cells and ctDNA (a subset of cell-free DNA [cfDNA]) may be appropriate when a patient is unfit for invasive tissue sampling, or insufficient material is available for molecular analysis.2,7 These assays have high specificity for detecting NSCLC mutations and can complement tissue testing to identify mutations more efficiently.2

In blood specimens, EGFR mutations related to lung adenocarcinoma can be detected with a pooled sensitivity (95% CI) of 66% (63%-70%) and a specificity of 96% (83%-99%)7; an FDA-approved “liquid biopsy” assay (test code 94718) is available to aid assessing eligibility for EGFR TKI therapy selection (Table 1). In the context of monitoring acquired resistance mutations, EGFR T790M can be detected with reported sensitivities of 40% to 78% in patients treated with EGFR TKIs.7 Overall, false-negative rates of up to 30% have been reported.2

Programmed death ligand 1 immunohistochemistry

NCCN recommends that programmed death ligand 1 (PD-L1) expression levels be measured in all metastatic NSCLC specimens before first-line treatment to assess patient eligibility for targeted FDA-approved therapies.2 PD-L1 expression in the tumor is associated with better response to programmed cell death protein 1 (PD-1)/PD-L1 inhibitor therapy. IHC assays using monoclonal antibodies specific for PD-L1 expression are required (companion) or optional (complementary) diagnostics to assess patient eligibility for treatment with immune checkpoint inhibitors. In NSCLC, PD-L1 expression is measured in tumor cells (TC) and tumor-infiltrating immune cells (IC) (lymphocytes, macrophages, dendritic cells, and granulocytes) and as a tumor proportion score (the percentage of viable tumor cells showing partial or complete membrane staining).15,16

Refer to PD-L1 Test Selection Guide for further information: https://testdirectory.questdiagnostics.com/test/test-guides/TG_PD-L1/pd-l1-test-selection-guide.