How Lung Cancer is Diagnosed?
Lung cancer can often be difficult to diagnose. It is common for a number of tests to be necessary in order to make a correct diagnosis. The radiological tests described below are usually used to detect a possible tumor. All pose some risk of radiation exposure, but if necessary to diagnose lung cancer, their benefits well outweigh their risks.
1. Radiological Tests
- Chest X-Ray: A CXR renders images of the blood vessels and organs of the chest. It is used to diagnose a number of conditions, including lung cancer. It is quick and pain-free.
- CT scan: A chest CT is like multiple CXRs added together, in which images through the chest can be formed like slices in a loaf of bread. It gives information on about the size and whereabouts of any tumors. This information in turn tells the doctor how to best treat the cancer.
- PET (positron emission tomography) scan: A PET scan is a non-invasive whole-body scan in which the patient is injected with a radioactive sugar that is labelled in a way that it can be located in the body. High concentrations of the sugar are commonly found in tumors with rapidly growing cells, but can also be in areas of infection. The areas of high concentration are seen as “bright” areas on the scan.
- Head CT scan or MRI: Similar to chest CT or MRI but gives information about possible spread of the tumor to the brain.
- Bone Scan: A whole body scan, similar to a PET scan, which uses a radioactive tracer to specifically identify possible sites of tumor spread to bones.
2. Invasive Diagnostic Tests
However, true conclusions cannot be made without a biopsy. This is therefore the role of the surgical tests. Usually, the least invasive procedure that will likely yield results is chosen, but this decision can sometimes be complicated. The less invasive the procedure, the more likely that the biopsy will not yield enough tissue for proper analysis. A more invasive approach must then be pursued to identify if there is cancer present, but requires surgery to remove all or a piece of the tumor.
- Fine Needle Aspiration (FNA): A minor procedure that uses fluoroscopy or CT guidance to obtain a biopsy.
- Risks: The biggest risk is a collapsed lung if the needle is inserted into the lung. Bleeding is also possible, and both of these complications may require placement of a tube for drainage of air or blood. It should also be noted that 25% of the time, the diagnosis may be missed and a more invasive procedure might then be used to obtain a conclusive diagnosis.
- Bronchoscopy: A long camerascope called a bronchoscope is inserted into the mouth or nose to look into the patient’s airway for possible biopsy of the tumor present in the airway.
- Risks: There is always risk with every procedure and all anesthetics. However, complications during a bronchoscopy are fairly rare, but include scratching of the airway and bleeding. Patients may be awake with local anesthesia to the airway, sedated, or put under general anesthesia for the procedure.
- Endobronchial Ultrasound: This procedure uses a bronchoscope which also has an ultrasound inside so that the doctor can perform a needle biopsy of lymph nodes that sit next to, but outside, the airway. This is done to determine if cancer has spread to these nearby lymph nodes.
- Risks: Those with bronchoscopy, but also bleeding from the biopsy site, collapsed lung, and failure to get enough tissue for an accurate diagnosis.
- Mediastinoscopy: This is a same-day surgical procedure that allows larger biopsies of the nearby lymph nodes to be obtained via a one inch incision on the neck just above your breast bone. General anesthesia is required and patients go home an hour or two after the procedure.
- Risks: Risks associated with general anesthesia and specifically, injury to nearby structures such as blood vessels, heart, nerves to vocal cords, stroke, or collapsed lung. Although very rare (less than 5 in 1,000 patients), these complications can result in major bleeding requiring emergency surgery, hoarseness, stroke, and even death.
- Thoracoscopy: This surgical procedure is typically performed under general anesthesia and involves a special breathing tube which allows the lung to be examined to be deflated. This allows the surgeon to insert a small camera and several small instruments between the ribs, so that the lung and lining can be examined and biopsies taken of suspicious areas. Usually a drainage tube is placed at the end of the procedure to drain any air or blood and can be removed a few hours or a few days later depending on the biopsies taken and drainage of the tube. Patients can generally go home the same day that the tube is removed, if pain control is good with pain medication taken by mouth.
- Risks: This is a more invasive procedure which requires general anesthesia. If your lung function is poor, you may not be a good candidate for this procedure. Specific risks include bleeding, prolonged air leak, and nerve and rib pain and infection.
- Thoracotomy: Another surgical procedure that is used to diagnose patients who cannot be diagnosed by other methods. It involves a large incision on the side of a chest, through which the tumor can be identified and biopsied.
- Risks: Risk of air leaks, infection/pneumonia, respiratory failure, and bleeding as well as risks associated with general anesthesia (blood clot to lungs, heart attack).