Newly Diagnosed Lung Cancer: Which Tests Do I Need Before Starting Treatment?

What must be known before choosing treatment?

It helps to organise the investigation process around four questions. This makes it easier to understand why a test has been requested, and whether an existing result already answers the question.

Your oncologist brings these findings together, often with input from a pathologist, radiologist, respiratory physician, surgeon and radiation oncologist. Ask who is coordinating the results and who you should contact if something has not arrived. A named next appointment can make a confusing period more manageable.

Has the exact type of lung cancer been confirmed?

A scan can suggest lung cancer, but a pathologist usually confirms the diagnosis by examining tissue or cells. A tissue biopsy preserves small pieces of tissue; cytology examines cells, for example from a needle sample or fluid. The report may include immunohistochemistry, laboratory stains that help identify what kind of cells are present.

The main distinction is between non-small-cell lung cancer (NSCLC), which includes adenocarcinoma and squamous-cell carcinoma, and small-cell lung cancer (SCLC). These have different treatment pathways. Sometimes additional examination is needed before the laboratory can confidently classify the sample.

The safest useful sample is not always taken directly from the lung mass. A suitable lymph node or another accessible site may provide the diagnosis and staging information together. Ask what the proposed procedure is expected to establish and whether enough material can be collected for further tests.

Which scans and lymph-node tests establish the stage?

Stage describes the extent of the cancer. It helps the team decide whether treatment should focus on the lung and surrounding area, use medicines throughout the body, or combine approaches. The investigations depend on the cancer type, existing findings, symptoms and treatment being considered.

A contrast-enhanced CT provides detailed pictures of the chest and other relevant areas. A PET-CT adds information about uptake of a tracer, helping to assess possible cancer sites. It is particularly useful when planning potentially curative treatment, but it is not an automatic requirement in every clinical situation. Brain magnetic resonance imaging (MRI) or CT may be needed depending on the diagnosis, stage and symptoms; the absence of a headache does not settle this question.

Some chest lymph nodes can be sampled using endobronchial ultrasound (EBUS), an ultrasound-guided examination through the airways, or another appropriate procedure. Confirmation can be important when a node finding would change the treatment plan. A PET-positive node is not necessarily cancer: inflammation and infection can also cause increased uptake.

Ask, “Is my stage established, or is there a particular finding that still needs checking?” Our guide to cancer in lymph nodes explains why a node result needs its own context.

Which tumour tests could change my first treatment?

Biomarkers are measurable features of the cancer. They can include changes in genes and the presence of particular proteins. The treatment-selection tests discussed below are mainly used in NSCLC. They can matter in selected earlier-stage situations as well as advanced disease. SCLC follows a different pathway: the same molecular panel and PD-L1 testing are not routinely needed to choose its initial treatment.

Molecular testing, sometimes called lung cancer genetic testing or genomic profiling, looks for changes in the cancer’s genes that may help guide targeted treatment. For advanced NSCLC, particularly adenocarcinoma, EGFR, ALK and ROS1 are three essential genes to check. EGFR stands for epidermal growth factor receptor and ALK for anaplastic lymphoma kinase; ROS1 is the name of another gene that can help drive cancer growth when altered. Testing only these three can miss other changes that matter for treatment. A validated broad panel is preferred where appropriate and available: it checks several relevant genes together, often using next-generation sequencing (NGS). Ask which genes and types of change the panel can detect. The tests needed depend on the cancer type, stage and treatment being considered.

PD-L1 is a protein assessed by a separate laboratory stain. Its result can help inform immunotherapy choices in the appropriate setting. It is not the same as a molecular panel. A high PD-L1 result does not remove the need for appropriate molecular testing or, by itself, establish the best first treatment.

Other protein tests, including tests for HER2 (human epidermal growth factor receptor 2, a protein involved in cell growth) or MET expression, may also be relevant to the NSCLC treatment pathway. A high level of a protein is not the same finding as a change in the corresponding gene. Ask your oncologist which results are needed now and which might be useful later; the report should identify exactly what was measured.

Testing should not be dismissed simply because someone has smoked. Smoking history can inform assessment, but it cannot reliably tell the team that an individual tumour has no relevant alteration. Most tumour testing also differs from testing for an inherited cancer risk; a tumour result does not automatically mean your relatives carry the same change.

Our biomarker testing guide explains how results are matched to treatment options. A test result alone does not establish that a medicine is suitable or available for you.

What if there is too little biopsy material?

An “insufficient tissue” result can mean there were enough cells to diagnose cancer, but too few for a particular additional test. It does not necessarily overturn the diagnosis. Ask whether another stored tissue block, a prepared cell sample or other material held by the original laboratory could be suitable before assuming that you need another procedure.

If more sampling is necessary, discuss the likely benefit, procedure risks and whether one sample can answer several outstanding questions. Coordination between the treating team and the laboratory helps make the best use of limited material.

A blood-based liquid biopsy looks for circulating tumour DNA, or ctDNA: fragments of tumour DNA released into the bloodstream. In appropriate circumstances it can complement tissue testing, including when tissue is limited or a faster molecular result is important. It usually does not replace the tissue or cell examination needed to establish the cancer type.

A negative or non-informative blood result cannot reliably exclude a relevant alteration. Some cancers release little detectable DNA, and assays have technical limits. Tissue testing or another sample may therefore still be needed. Ask whether “negative” means the laboratory found no target despite an informative sample, or could not obtain a useful answer.

What checks show whether treatment can be given safely?

Tell the team how you are managing ordinary activities, eating, sleeping and breathing. Describe what has changed recently, including weight loss, pain or difficulty walking. This helps assess performance status, the effect of illness on daily function, alongside other medical conditions.

Blood counts and kidney, liver and other blood chemistry tests help assess health and plan treatment safely. These are different from tests looking for tumour biomarkers. Bring a complete medicines list, including non-prescription products, supplements and allergies.

Lung-function tests are part of assessment before lung surgery and may also be needed before treatments such as radiotherapy to the chest. Heart investigations depend on symptoms, medical history and the treatment proposed. You do not need every possible fitness test simply because you have lung cancer.

Ask whether breathlessness, nutrition, another illness or a medicine needs attention while the cancer plan is being completed. Supportive treatment can be part of preparation, rather than something that begins only after the first cancer treatment.

Should treatment wait until all results are back?

The useful question is, “Which results do we need before making this decision, and how urgent is treatment in my situation?” Some results can change the initial medicine or sequence. Others may not affect the immediate next step. Your team needs to balance the value of missing information against symptoms, disease behaviour and the risks of waiting.

There is no universally safe waiting period. Ask for the expected reporting date, the review appointment and a contingency plan if a result is delayed. Do not cancel or postpone recommended treatment while arranging tests or another opinion without discussing this with your treating team.

Seek emergency medical care for severe or rapidly worsening breathing difficulty, coughing up more than a few spots or streaks of blood, or new neurological symptoms such as weakness, confusion or a seizure. Even small streaks of blood in your sputum should be reported promptly to your team. Do not wait for a routine report-review appointment.

What should I bring to my lung cancer consultation?

Bring the records you already have. You can use this checklist to organise the discussion rather than order investigations yourself.

Five useful questions are:

1. What exact type of lung cancer has been confirmed?
2. What is the stage, and is anything still uncertain?
3. Are the appropriate biomarkers available before the first treatment decision?
4. Would another sample or blood test change what we do?
5. What happens next, when, and whom should I contact if I become more unwell?

Bringing the discussion together

You do not need to resolve every question on your own. Bring your available reports and the questions that matter most to your treating team. Before leaving, check that you understand the agreed next step, when it should happen and whom to contact if you need help.