NGS Testing Before Lung Cancer Treatment: Why Is It a Must? (2026 Update)

NGS (next-generation sequencing) is a test that checks multiple genetic alterations at once — such as EGFR, ALK, and ROS1 — and for advanced or metastatic non-small cell lung cancer, treatment decisions cannot be made without these results, which is why the test is recommended before treatment begins.

Key Takeaways

• NGS is a test that checks multiple genetic alterations at once from tissue or blood samples, including EGFR, ALK, ROS1, BRAF, KRAS, MET, RET, and NTRK.
• For advanced or metastatic non-small cell lung cancer, treatment can only be determined once both the stage and biomarker results are known; the NCCN patient guidelines also describe biomarker testing as a standard step before starting treatment (NCCN).
• If a biomarker is detected, treatment begins with an oral targeted therapy aimed at that specific gene; if not, treatment instead starts based on PD-L1 expression, using immune checkpoint inhibitors or combination chemotherapy — meaning the entire treatment pathway changes depending on the result.
• East Asian patients are known to have a relatively higher rate of EGFR mutations, so biomarker testing is especially important even in lung cancer patients who have never smoked.
• Depending on the panel, results typically take anywhere from a few days to 2–3 weeks; if local results already exist, they can be used directly, and if not, tissue slides can be sent to Korea for testing.

What Exactly Does NGS Testing Look At?

• NGS is a biomarker test that simultaneously reads changes across multiple genes from tissue or blood to guide treatment selection; it is different from genetic counseling tests that look for inherited mutations (U.S. National Cancer Institute, NCI).
• In lung cancer, drug selection requires checking genetic alterations such as EGFR, ALK, ROS1, BRAF, KRAS, MET, RET, and NTRK together with PD-L1 expression. When tissue is difficult to obtain, a blood-based test that examines circulating tumor DNA may be used instead.
• Targeted therapies are drug treatments that specifically target particular proteins or gene mutations that cancer cells use to grow, and the same drug has little to no effect on patients who do not carry that specific mutation (National Cancer Information Center).

How Does the Treatment Path Change Based on Test Results? (Step by Step)

1. Step 1 — A suspicious lesion is identified on chest CT, and tissue is obtained via bronchoscopy or needle biopsy to determine whether it is non-small cell or small cell lung cancer.
2. Step 2 — PET-CT and brain MRI are used to determine the stage, while NGS biomarker testing is performed in parallel using tissue or blood.
3. Step 3 — If a target such as EGFR or ALK is confirmed in stage 4 non-small cell lung cancer, treatment begins with the corresponding oral targeted therapy.
4. Step 4 — If no target is found, treatment begins based on PD-L1 expression and tumor histology, using either immune checkpoint inhibitors alone or in combination with chemotherapy.
5. Step 5 — While a drug remains effective, CT scans are typically done every 2–3 months to check response; if resistance develops, retesting is done before moving on to the next drug, which is the general treatment flow.

FAQ — Can I Use Genetic Test Results I Already Received Locally?

If local results are recent and cover sufficient markers, they can be used as-is. If results are missing, outdated, or lacking necessary markers, tissue slides or paraffin blocks can be sent for NGS testing in Korea, or testing can be done after arrival — which option applies will be advised during the review stage.

FAQ — I've Never Smoked. Do I Still Need NGS Testing?

Lung cancers that occur in never-smokers are known to have a higher rate of genetic alterations such as EGFR and ALK, making biomarker testing especially important regardless of smoking history. If a target is confirmed, oral targeted therapy becomes an option; if not, immunotherapy or chemotherapy becomes the standard approach.

Sources and Notes

• This article was written based on notes regarding lung cancer, targeted therapy, and pre-treatment checklists (National Cancer Information Center, National Cancer Center Korea, NCCN patient guidelines, U.S. National Cancer Institute (NCI), SEER).
• This content is intended for general medical information purposes only, and actual diagnosis, treatment methods, and outcomes may vary depending on individual circumstances. Accurate diagnosis and treatment should always be determined through consultation with a medical professional.