How is lung cancer diagnosed?

The first test is usually a chest 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 having the scan.

Immediately 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 have nausea (feel sick) or feel a sudden urge to pass urine (pee or wee). These sensations should go away quickly, but tell your doctor if you continue to 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. Getting ready for the scan can take 10–30 minutes, but the scan itself takes only a few minutes and is painless.

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. The Australian Government is considering introducing a lung cancer screening program.

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. For a lung function test, 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.

PET–CT scan

This scan combines a PET (positron emission tomography) scan with a CT scan in one machine. As well as helping with diagnosis, a PET–CT scan can provide detailed information about any cancer that is found.

First, 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. The scan will take about 30 minutes.

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. You will need to fast (not eat or drink) before having this scan.

Biopsy

The most common way to confirm a lung cancer diagnosis is by biopsy. A small sample of tissue is taken from the lung, the nearby lymph nodes, or both. The tissue 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.

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.

CT-guided lung biopsy – First, you will be given a local anaesthetic. Then, using a CT scan for guidance, the doctor inserts a needle through the chest wall to remove a small sample of tumour from the outer part of the lungs.

You will be monitored for a few hours afterwards. There is a small risk of damaging the lung, but this can be treated if it does occur.

Bronchoscopy – The doctor will look inside the large airways (bronchi) using a bronchoscope, a flexible tube with a light and camera.

A bronchosopy is usually performed under light sedation, so you will be awake but feel relaxed and drowsy. You will also be given a local anaesthetic (a mouth spray or gargle) so you don’t feel any pain during the procedure. The doctor will then 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 using either 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 possible, the doctor will use small forceps to take a tissue sample for biopsy.

Endobronchial ultrasound (EBUS) – This is a type of bronchoscopy that allows the doctor to see a cancer deeper in the lung. During this test, the doctor may also take cell samples from a tumour, from the outer parts of the lung, or from lymph nodes in the area of your chest between your lungs (mediastinum). Samples from the lymph nodes can help to confirm whether or not they are also affected by cancer.

You will have light sedation and local anaesthetic, or a general anaesthetic. The doctor will then put a bronchoscope (a thin tube with a small ultrasound probe on the end) into your mouth. The bronchoscope will be passed down your throat until it reaches the bronchi.

The ultrasound probe uses soundwaves to create pictures that show the size and position of a tumour.

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.

Endoscopic ultrasound – Sometimes, an endoscopic ultrasound is used to check whether the lung cancer has spread to the lymph nodes in the mediastinum. In an endoscopic ultrasound, a probe is passed into your mouth and down your oesophagus and a cell sample is taken from the lymph nodes.

Mediastinoscopy – This type of biopsy is not used often but may be done if larger samples from the lymph nodes found in the area between the lungs (mediastinum) are needed. 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 stay 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 (VATS). Sometimes a simpler procedure called a medical thoracoscopy can be done as a day procedure, because only light  sedation is needed.

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.

Other biopsies – If there is concern that the cancer may have spread to other organs, such as the brain, different types of biopsies may be done.

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 – In this test, a sample of mucus from your lungs (called sputum or phlegm) is examined to see if there are cancer cells. Sputum contains cells that line the airways, and is not the same as saliva.

To collect a sample for this test, you will be asked to cough deeply and forcefully into a container. You can do this at home in the morning before eating or drinking.

The sample can be kept 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. A pleural tap 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.

Biopsy samples may be tested for gene 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.

Gene 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 (acquired mutation) is not the same thing as genes inherited from your parents. Most gene changes linked to lung cancer are not inherited.

In NSCLC, the most common genetic mutations are changes in the EGFR (epidermal growth factor receptor), ALK (anaplastic lymphoma kinase), ROS1 (ROS proto-oncogene 1), and KRAS (Kirsten rat sarcoma virus) genes. Lung cancers with these gene mutations can be treated with a type of medicine called targeted therapy.

Proteins – If certain proteins are found in the biopsy sample from a NSCLC, the cancer may respond to immunotherapy. The most common protein tested for is called PD-L1 (programmed death ligand-1).

If the tests show that you have lung cancer, you will have further tests to see whether the cancer has spread beyond the lung to other parts of the body. You may also have a CT or MRI (magnetic resonance imaging) scan of the brain.

If a PET–CT scan is not available or the results are unclear, you may have a CT scan of the abdomen (belly) or a bone scan. For more information, talk to your doctor or call Cancer Council 13 11 20.