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How is lung cancer diagnosed?

Your doctors will arrange several tests to make a diagnosis and work out if the cancer has spread beyond the lung. The test results will help them recommend a treatment plan for you.

The first test is usually an x-ray, which is often followed by a CT scan. You may also have a breathing test to check how your lungs are working and blood tests to check your overall health.

Chest x-ray

A chest x-ray is painless and can show tumours 1 cm wide or larger. Small tumours may not show up on an x-ray or may be hidden by other organs within the chest cavity.

CT scan

A CT (computerised tomography) scan uses x-ray beams to create detailed, cross-sectional pictures of the inside of your body. This scan can detect smaller tumours than those found by chest x-rays. It provides detailed information about the tumour, the lymph nodes in the chest and other organs.

CT scans are usually done at a hospital or radiology clinic. You may be asked to fast (not eat or drink) for several hours before the scan. Before the scan, you will be given an injection of a liquid dye into a vein. This dye is known as contrast, and it makes the pictures clearer. The contrast may make you feel hot all over and leave a bitter taste in your mouth, and you may feel a sudden urge to pass urine. These sensations should go away quickly, but tell your doctor if you feel unwell.

The CT scanner is a large, doughnut-shaped machine. You will need to lie still on a table while the scanner moves around you. The scan itself is painless and takes only a few minutes, but getting ready for it can take 10–30 minutes.

A low-dose CT scan may be useful for screening healthy people for lung cancer or to follow-up suspicious-looking spots in the lungs. This uses a lower dose of radiation than a regular CT scan and provides a more detailed image than an x-ray. Currently, the Australian Government is looking at how low-dose CT screening could be used in Australia.

Lung function test (spirometry)

This test checks how well the lungs are working. It measures how much air the lungs can hold and how quickly the lungs can be filled with air and then emptied. You will be asked to take a full breath in and then blow out into a machine called a spirometer. You may also have a lung function test before you have surgery or radiation therapy.

Blood tests

A sample of your blood will be tested to check the number of red blood cells, white blood cells and platelets (full blood count), and to see how well your kidneys and liver are working.

If a tumour is suspected after an x-ray or CT scan, you will need further tests to work out if it is lung cancer.

Biopsy

A biopsy is the usual way to confirm a lung cancer diagnosis. A small sample of tissue is taken from the lung, the nearby lymph nodes, or both. The biopsy sample is sent to a laboratory, where a specialist doctor called a pathologist looks at the sample under a microscope. There are various ways to take a biopsy.

CT-guided lung biopsy – You will be given a local anaesthetic. Using a CT scan for guidance, the doctor inserts a needle through the chest wall to remove a small piece of tumour from the outer part of the lungs. You will be monitored for a few hours afterwards, as there is a small risk of damaging the lung. This can be treated if it does occur.

Bronchoscopy – This allows the doctor to look inside the large airways (bronchi) using a bronchoscope, a flexible tube with a light and camera. You will be given either sedation or a light general anaesthetic, then the doctor will pass the bronchoscope into your nose or mouth, down the trachea (windpipe) and into the bronchi. If the tumour is near the bronchi, samples of cells can be collected with a washing or brushing method. During “washing”, fluid is injected into the lung and then removed to be looked at under a microscope. “Brushing” uses a brush-like instrument to remove some cells from the bronchi. If the doctor sees a tumour, they will take a sample.

Endobronchial ultrasound (EBUS) – This is a type of bronchoscopy that allows the doctor to see a cancer deeper in the lung. It can also take samples of cells from a tumour or a lymph node in the middle of your chest or next to the airways, or from the outer parts of the lung.

You will have sedation or a general anaesthetic, and the doctor will put a bronchoscope with a small ultrasound probe on the end into your mouth. The ultrasound probe uses soundwaves to create pictures that show the size and position of a tumour. This allows the doctor to measure the tumour and take samples.

After a bronchoscopy, you may have a sore throat or cough up a small amount of blood. These side effects usually pass quickly, but tell your medical team how you are feeling so they can monitor you.

Mediastinoscopy – This type of biopsy is not used often but may be done if a sample is needed from the lymph nodes found in the area between the lungs (mediastinum). You will have a general anaesthetic, then the surgeon will make a small cut (incision) in the front of your neck and pass a thin tube down the outside of the trachea. You can usually go home on the same day as having a mediastinoscopy, but sometimes you may need to be monitored overnight in hospital.

Thoracoscopy – If other tests are unable to provide a diagnosis, you may have a thoracoscopy. This uses a thoracoscope, a tube with a light and camera, to take a tissue sample from the lungs. It is usually done under general anaesthetic with a type of keyhole surgery called video-assisted thoracoscopic surgery. Sometimes a simpler procedure called a medical thoracoscopy can be done as a day procedure. This is done when you are under sedation.

Biopsy of neck lymph nodes – The doctor may take a sample of cells from the lymph nodes in the neck with a thin needle. This is often done using ultrasound for guidance.

A new test known as liquid biopsy involves taking a blood sample and examining it for cancer. Liquid biopsy is still being studied to see how accurate it is, and it is not a routine way to diagnose lung cancer.

In some circumstances, such as if you aren’t well enough for a biopsy, mucus or fluid from your lungs may be checked for abnormal cells.

Sputum cytology

This test examines a sample of mucus (sputum) from your lungs to see if there are any cancer cells. Sputum is different from saliva as it contains cells that line the airways. To collect a sample, you will be asked to cough deeply and forcefully into a container. This can be done in the morning at home. You can keep the sample in your fridge until you take it to your doctor, who will send it to a laboratory to check under a microscope.

Pleural tap

Also known as pleurocentesis or thoracentesis, this procedure drains fluid from around the lungs. It can help to ease breathlessness, and the fluid can be tested for cancer cells. It is mostly done with a local anaesthetic, with the doctor using ultrasound to guide the procedure. As with all biopsies, the results need to be interpreted along with the results of physical examination, blood and breathing tests, and imaging tests such as x-ray and CT scan.

The biopsy sample may be tested for genetic changes or specific proteins in the cancer cells (biomarkers). These tests are known as molecular tests and they help work out which drugs may work best in treating the cancer.

Genetic changes

Genes are found in every cell of the body and are inherited from both parents. If something triggers the genes to change (mutate), cancer may start growing. A mutation that occurs after you are born is not the same thing as genes inherited from your parents. The most common genetic mutations seen in non-small cell lung cancer (NSCLC) are changes in the EGFR (epidermal growth factor receptor), ALK (anaplastic lymphoma kinase) and ROS1 genes. These three mutations can be treated with medicines known as targeted therapy. Other mutations linked to NSCLC (such as KRAS) do not yet have a targeted therapy available to treat them.

Proteins

The presence and amount of certain proteins found in the biopsy sample from a NSCLC may suggest the cancer will respond to immunotherapy. The most common protein tested for is called PD-L1.

If the tests show that you have lung cancer, you will have further tests to see whether the cancer has spread to other parts of your body.

PET–CT scan

This scan combines a PET (positron emission tomography) scan with a CT scan in one machine. It can provide detailed information about the cancer.

A small amount of radioactive glucose solution is injected into a vein, usually in your arm. You will be asked to sit quietly for 30–90 minutes while the glucose solution travels around your body, then you will lie on a table that moves through the scanning machine very slowly. Cancer cells take up more of the glucose solution than normal cells do, so they show up more brightly on the scan.

Sometimes a PET–CT scan is done to work out if a biopsy is needed or to help guide the biopsy procedure.

Other tests

You may also have a CT or MRI (magnetic resonance imaging) scan of the brain. If a PET–CT scan is not available or results are unclear, you may have a CT scan of the abdomen or a bone scan. For more details, talk to your doctor or call Cancer Council 13 11 20.

This information is reviewed by

This information was last reviewed in October 2020 by the following expert content reviewers: A/Prof Nick Pavlakis, President, Australasian Lung Cancer Trials Group, President, Clinical Oncology Society of Australia, and Senior Staff Specialist, Department of Medical Oncology, Royal North Shore Hospital, NSW; Dr Naveed Alam, Thoracic Surgeon, St Vincent’s Private Hospital Melbourne, VIC; Prof Kwun Fong, Thoracic and Sleep Physician and Director, UQ Thoracic Research Centre, The Prince Charles Hospital, and Professor of Medicine, The University of Queensland, QLD; Renae Grundy, Clinical Nurse Consultant – Lung, Royal Hobart Hospital, TAS; A/Prof Brian Le, Director, Palliative Care, Victorian Comprehensive Cancer Centre – Peter MacCallum Cancer Centre and The Royal Melbourne Hospital, and The University Of Melbourne, VIC; A/Prof Margot Lehman, Senior Radiation Oncologist and Director, Radiation Oncology, Princess Alexandra Hospital, QLD; Susana Lloyd, Consumer; Caitriona Nienaber, 13 11 20 Consultant, Cancer Council WA; Nicole Parkinson, Lung Cancer Support Nurse, Lung Foundation Australia.