Detecting Lung Cancer: Hospital Testing Procedures

Lung cancer is a serious condition that often doesn't exhibit symptoms until it has reached an advanced stage. Testing for lung cancer typically involves a series of imaging tests and biopsies, with the goal of early detection, when treatment is more likely to be successful. The tests used to detect lung cancer include chest x-rays, CT scans, PET-CT scans, ultrasounds, MRI scans, and various biopsy procedures. The choice of test depends on the patient's situation and symptoms.

Chest X-rays

X-ray images are not high-resolution, and it is easy to miss subtle details. Normal body parts like bones can obscure tumours, especially if they are small. In addition, certain diseases can also make cancerous growths hard to see. For example, pneumonia is commonly associated with symptomatic lung cancer, and the pus and mucus that clog the airways can easily hide a tumour.

While chest X-rays can sometimes detect larger tumours, they often fail to diagnose lung cancer, especially in its early stages. Advanced lung cancer found in stage 3b or 4 is challenging to treat and often incurable. Therefore, chest X-rays are not recommended for lung cancer screening. Instead, low-dose computed tomography (LDCT) scans are now the standard for lung cancer screening in high-risk individuals.

CT scans

One variation of a CT scan is the low-dose CT (LDCT) scan, which is recommended for lung cancer screening in high-risk individuals, especially those with a history of smoking. LDCT scans use a lower dose of radiation than standard CT scans, making them a safer option for regular screening. These scans can help detect lung cancer early on, when treatment is more likely to be effective. However, it's important to note that even LDCT scans expose individuals to radiation, and repeated scans can increase the risk of cancer in healthy individuals.

Another specialised type of CT scan is the PET-CT scan, which combines a CT scan with a positron emission tomography (PET) scan. The PET component uses a mildly radioactive drug to highlight areas of increased cellular activity, which often indicates cancerous growth. By combining PET and CT technologies, doctors can more accurately determine the presence and spread of cancer throughout the body. PET-CT scans are particularly useful for cancer staging, helping doctors decide on the best treatment approach.

PET-CT scans

During a PET scan, a slightly radioactive form of sugar, called fluorodeoxyglucose (FDG), is injected into the patient's blood. This substance collects mainly in cancer cells, as they tend to take up more sugar than normal cells. The PET scan shows areas of higher radioactivity, which may indicate the presence of cancer.

The CT scan, on the other hand, takes a series of X-rays from different angles around the body and combines them to create detailed, cross-sectional 3D images. These images help doctors visualise the size, shape, and position of any lung tumours, as well as identify enlarged lymph nodes or masses in other parts of the body that could indicate the spread of cancer.

When combined, the PET-CT scan allows doctors to compare areas of higher radioactivity on the PET scan with the detailed images of the CT scan. This helps them accurately stage the cancer, understanding if and where it has spread.

However, there are some limitations to PET-CT scans. For instance, they are not suitable for examining the brain or spinal cord, and false-negative results can occur due to the limited spatial resolution of PET cameras, which may miss lesions smaller than 1 cm. Additionally, patient-specific factors such as body size, blood glucose concentration, and timing of the scan can hinder the interpretation of results, especially in diabetic patients.

Biopsies

There are several types of lung biopsies, each performed differently:

Needle Biopsy

A needle biopsy is a common type of lung biopsy where a long, hollow needle is inserted into the lung via the chest to extract a tissue sample. This procedure is usually performed under local anaesthesia, so the patient is awake but comfortable. It typically takes 30 to 45 minutes, and while it is not painful, patients may feel some pressure when the needle is inserted. After the procedure, patients are advised to rest for a few days and follow aftercare instructions to keep the biopsy incision site clean.

Transbronchial Biopsy

A transbronchial biopsy is a type of needle biopsy where the needle is guided through the bronchi, the large airways leading to the lungs. This type of biopsy is often used when the suspicious area is deep within the body or hard to reach.

Thoracoscopic Biopsy

A thoracoscope, a small tube with a camera on the end, is inserted into the body through a small incision in the chest wall to obtain a tissue sample. This procedure may be performed under general anaesthesia.

Open Lung Biopsy

An open lung biopsy involves surgical removal of lung tissue under general anaesthesia. A small incision is made in the chest, and the ribs are gently separated to access the lung tissue. The incision is then closed with stitches, and patients may remain on a breathing tube for a while post-surgery.

Percutaneous Transthoracic Lung Biopsy (PTLB)

This type of biopsy involves inserting a needle through the chest wall, guided by a CT scan or fluoroscopy, to reach the suspected area and obtain a tissue sample.

Video-Assisted Thoracic Surgery (VATS)

VATS is an endoscopic procedure where lung tissue is removed via the chest wall without the need for a large incision.

Transbronchial Cryobiopsy

Transbronchial cryobiopsy involves freezing and removing a tissue sample with the use of nitrous oxide and a specialised flexible probe.

Screening tests

While LDCT is the primary screening test, other imaging tests may be used for screening and diagnosis. Chest x-rays, for example, are often the first test performed to look for any abnormal areas in the lungs. However, chest x-rays are not recommended for lung cancer screening as they have not been shown to improve survival rates.

If a suspicious area is detected during screening, further tests may be required for diagnosis. These include CT-guided needle biopsies, where a needle is guided by CT imaging to extract a tissue sample from the suspicious area. MRI scans may also be used to look for the possible spread of cancer to the brain, spinal cord, or liver. These scans use radio waves and strong magnets to create detailed images of soft tissues in the body.

Another diagnostic test is a PET/CT scan, which combines positron emission tomography (PET) with a CT scan. The PET scan uses a mildly radioactive drug to highlight areas of increased cellular activity, while the CT scan provides detailed images. This combination allows doctors to compare areas of higher radioactivity with detailed anatomical images, aiding in cancer staging and determining if cancer cells are present and where they have spread.

It is important to note that screening and diagnostic tests for lung cancer are generally recommended for adults at high risk of developing the disease due to their smoking history and age. People experiencing symptoms such as breathlessness or a persistent cough should consult a doctor, who can determine the appropriate tests and refer them to a screening facility if necessary.

Frequently asked questions