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Diagnosing lung cancer
Diagnosis is the process of finding the cause of a health problem. The process of diagnosis may seem long and frustrating, but it is important for the doctor to rule out other reasons for a health problem before making a cancer diagnosis. Diagnostic tests for lung cancer are usually done when:
- the symptoms of lung cancer are present
- the doctor suspects lung cancer after talking with a person about their health and completing a physical examination
Many of the same tests used to initially diagnose cancer are used to determine the stage (how far the cancer has progressed). Your doctor may also order other tests to check your general health and to help plan your treatment. Tests may include the following.
The medical history is a record of present symptoms, risk factors and all the medical events and problems a person has had in the past. The medical history of a person’s family may also help the doctor to diagnose lung cancer.
In taking a medical history, the doctor will ask questions about:
- a personal history of
- exposure to second-hand smoke
- occupational or environmental risk factors
- lung cancer or lung disease
- radiation therapy to the chest
- a family history of
- lung cancer
- risk factors that may increase the risk of developing lung cancer
- other cancers
- sign and symptoms that may suggest lung cancer
A physical examination allows the doctor to look for any signs of lung cancer. During a physical examination, the doctor may:
- check breathing
- listen to the lungs using a stethoscope
- tap the chest to hear percussion sounds
- look at the movement of the chest during breathing
- feel the neck and area above the collarbone for swelling or enlarged lymph nodes
- feel the abdomen for an enlarged liver or a lump
- check blood pressure and pulse
- listen to the heart with a stethoscope
An x-ray uses small doses of radiation to make an image of the body’s structures on film. A chest x-ray is often the first test done to diagnose lung cancer. It is used to look for any spots, tumours or changes in the lungs.
A CT scan uses special x-ray equipment to make 3-dimensional and cross-sectional images of organs, tissues, bones and blood vessels inside the body. A computer turns the images into detailed pictures. It is used to:
- show the location, size and shape of a lung tumour
- A CT scan may find an early stage lung tumour that can’t be seen on a chest x-ray.
- find any enlarged lymph nodes in the chest
- look for any spread of the tumour to other parts of the body
- Lung cancer may spread to the adrenal glands, liver or brain.
- guide a biopsy
A PET scan uses radioactive materials (radiopharmaceuticals) to detect changes in the metabolic activity of body tissues. A computer analyzes the radioactive patterns and makes 3-dimensional colour images of the area being scanned.
PET scans may be used to find out if lung cancer has spread to the lymph nodes or other structures in the chest.
Mucus that is coughed up from the lungs (sputum) may be examined for the presence of cancer cells. Several sputum samples are collected, usually in the early morning. If people have trouble coughing up sputum, they may be given a mist to inhale to help them cough.
An endoscopic procedure may be done to diagnose and stage non–small lung cancer (NSCLC). It allows a doctor to look inside body cavities using a flexible tube with a light and lens on the end (an endoscope). Endoscopic procedures used to diagnose and stage lung cancer include:
- A bronchoscopy may be done to look for a tumour inside the bronchi.
- During a bronchoscopy, the doctor may remove a sample of tissue or fluid to be examined under a microscope to diagnose non–small lung cancer.
- mediastinoscopy or mediastinotomy
- A mediastinoscopy may be done to look at the mediastinummediastinumThe space in the chest between the lungs, breastbone and spine that contains the heart, great blood vessels, thymus, trachea (windpipe), esophagus and lymph nodes. and get samples of tissues in the area.
- A mediastinotomy is similar to mediastinoscopy. Instead of inserting an endoscope through a cut in the neck, the doctor makes a slightly larger incision between the ribs. This allows the doctor to examine lymph nodes that cannot be reached by a mediastinoscopy.
- thoracoscopy (pleuroscopy)
- A thoracoscopy may be done to look at and sample tissue from the chest wall, mediastinum, outer lining of the lungs (pleura) and lymph nodes in the chest.
- Thoracoscopy is not often done to diagnose lung cancer. It may be used if other tests, such as bronchoscopy, cannot get enough tissue to make a diagnosis.
Ultrasound uses high-frequency sound waves to make images of structures in the body. It is used:
- in combination with bronchoscopy (endobronchial ultrasound) to look at and take samples from the lymph nodes in the mediastinum
- to look for any fluid in the lungs or chest
During a biopsy, tissues or cells are removed from the body so they can be tested in a laboratory. The pathology report from the laboratory will confirm whether or not cancer cells are present in the sample. The biopsies that could be used for lung cancer are:
- fine needle aspiration (FNA)
- The doctor may use a CT scan to guide FNA to remove a small amount of tissue from a suspected lung tumour or from a lymph node in the chest.
- FNA may also be done during bronchoscopy, along with endobronchial ultrasound, to take samples of lymph nodes around the trachea and the bronchi.
- Thoracentesis may be done to remove fluid from around the lungs to see if it contains cancer cells.
MRI uses powerful magnetic forces and radio-frequency waves to make cross-sectional images of organs, tissues, bones and blood vessels. A computer turns the images into 3-dimensional pictures. It is used to look for lung cancer that has spread to the brain or spinal cord.
An MRI of the heart (cardiac MRI) may be done before surgery to look for any problems or changes in the heart that may prevent a person from having surgery.
A bone scan uses bone-seeking radioactive materials (radiopharmaceuticals) and a computer to create a picture of the bones. It is used to look for lung cancer that has spread to the bone (bone metastases) in people who have:
- bone pain
- blood chemistry tests that suggest that cancer has spread to the bone, including higher than normal levels of
- alkaline phosphatase (ALP)
Molecular tissue tests look for certain changes in the genes of non–small cell lung cancer cells. These genetic mutations may change how much or the type of protein the cancer cells produce. These changes may affect the type of treatment given because some chemotherapy drugs may be more effective against cancer cells with these changes. Molecular tissue tests may also help predict prognosis.
Molecular tissue tests for non-small cell lung cancer look for the genes responsible for:
- epidermal growth factor receptor (EGFR)
- anaplastic lymphoma fusion (ALK)
Specific mutations in these genes are associated with a better response to some drugs.
A complete blood count (CBC) measures the number and quality of white blood cells, red blood cells and platelets. A CBC is done to provide basic information about the person’s general health before treatment starts.
Blood chemistry tests measure certain chemicals in the blood. They show how well certain organs are functioning and can also be used to detect abnormalities. They are used to stage lung cancer.
- Increased alkaline phosphatase (ALP), calcium or phosphorus may indicate that the cancer has spread to the bone.
- Increased lactate dehydrogenase (LDH), alanine aminotransferase (ALT), aspartate transaminase (AST) and bilirubin may indicate that the cancer has spread to the liver.
Pulmonary function tests (also called lung function tests) check how well the lungs are working. They measure how much air the lungs can hold and how well the person can let air out of the lungs. These tests are important if doctors are considering surgery as a treatment option for non–small cell lung cancer. These tests help make sure that the person will have enough lung capacity after a lung or part of a lung is removed.
A pulmonary ventilation/perfusion scan (lung scan or VQ scan) is a nuclear scan that uses 2 tests to look at the blood supply of the lungs and how well air moves through the lungs. It is used if doctors are considering surgery as a treatment option. This test helps make sure that a person’s remaining lung is healthy and that the person will be able to tolerate surgery.
A chest x-ray is done before the VQ scan so the doctors can compare the results of both tests.
In the perfusion scan, a radioisotoperadioisotopeA substance or element that gives off radiation. is injected into a vein. A scanning machine is used to look at the lungs as the blood with the radioactive particles flows through the arteries of the lungs. The pictures from the machine show any problems with the blood supply of the lungs.
During the ventilation scan, the person breathes a radioactive gas through a mask while the scanner is used to watch the air flow in the lungs.
The doctor may order heart function tests to make sure that the person’s heart is healthy enough to tolerate and recover from lung cancer surgery. The tests that may be used are:
An arterial blood gas is a test that measures the amount of oxygen and carbon dioxide in the blood. It also measures the acidity (pH) of the blood. Arterial blood gas may be done to check how well the lungs are working, if doctors are considering surgery as a treatment option.
A small needle is used to take blood from an artery (usually the artery in the wrist). Afterwards, pressure is applied for a few minutes to stop bleeding.
The blood sample is taken to the laboratory immediately to make sure the results are accurate.