Lung cancers can be found by screening, like during a visit to your primary care physician, or by elective imaging studies, such as chest radiographs or computed tomography (CT) imaging. However, most lung cancers are discovered once they begin causing symptoms, such as shortness of breath, undesired weight loss, or pain.
At your doctor’s visit, your physician will begin by taking a detailed medical history and then perform a physical exam. If these lead him or her to believe you may have lung cancer, further tests will be ordered, which may include blood tests, imaging studies, or a lung biopsy.
A chest x-ray or radiograph will usually be the first study performed as it is convenient, cheap, and will reveal many lung cancers as a mass or shadow in the lungs. If the physician is suspicious for lung cancer, additional imaging studies will likely be obtained.
A CT scan also uses x-rays to generate an image, but it has several advantages compared to the chest x-ray. It will show the precise location, shape, and size of masses. In order to obtain even sharper images, some patients are asked to drink or receive IV contrast. This contrast makes some tissues appear brighter, which makes the images and the structures more apparent and easier to discern. Allergies to contrast medium may cause hives, flushing, shortness of breath, and low blood pressure. If you have had a reaction to contrast before, you should inform your physician. In addition to masses (such as cancers), it can show enlarged lymph nodes, which may have cancer cells. Many patients will have CT scans of the chest, as well as the abdomen to look for cancer spread, which may involve the liver, adrenal glands, or other internal organs. The CT scan may also involve the brain to look for cancer metastasis. A CT scan may also be used to obtain biopsies of masses or cancers what lie deep within or nearby other vital structures, which is termed CT guided needle biopsy.
A magnetic resonance imaging (MRI) study also provides detailed soft tissue “pictures.” As opposed to CT scans, which utilizes x-rays, MRIs use magnetic radiowaves to generate images. MRIs are particularly useful for imaging the brain and spinal cord. Gadolinium, a contrast, is often used to produce even better MRI images.
PET scans, also known as positron emission tomography, are especially useful to look for cancer spread. This study involves injecting a special radioactive sugar (flurodeoxyglucose, or FDP) into the vein. The amount of radioactivity is very low and will not cause you harm. After the injection, a special scanner will pickup areas in your body where the sugar has accumulated. As cancer cells are very active and require a great amount of energy (sugar), the FDP will concentrate in these areas. The PET scan does not produce extremely detailed images, but rather indicates spread of cancer throughout the body.
A similar test to the PET scan is the bone scan. During this procedure a specific substance that accumulates in rapidly changing areas of bone is injected in the vein. Areas of bone “turnover” such as areas of cancer show vividly on the scan.
A medical history, physical exam, and imaging studies may all suggest the diagnosis of lung cancer, but only the following tests can actually confirm a diagnosis of lung cancer:
- Sputum cytology – cells are collected from lung secretions (usually obtained from deep coughs early in the morning) and then examined under the microscope
- Thoracentesis – in the event that there is fluid around the lungs, which is termed a pleural effusion, doctors may insert a needle to drain the fluid to improve symptoms, such as shortness of breath because this fluid may impair the ability of air to enter and to exit the lungs. This fluid can then be examined for the presence of lung cancer cells under the microscope. Chemical tests can also be used to differentiate fluid with cancer cells from that without cancer cells.
- Needle biopsy – to avoid a surgical incision, a doctor may wish to obtain cells from a suspicious mass via a needle biopsy. He or she can use a very thin, hollow needle and perform a fine needle aspiration (FNA). However a FNA risks not obtaining sufficient amount of tissue for a definitive diagnosis. To obtain more tissue, one can use a larger needle in a procedure termed a core biopsy. If the mass is in the outer portion of the lung, the physician may pass the needle through the chest wall skin to obtain the sample, which is termed a transthoracic needle biopsy. If the biopsy is performed while performing a bronchoscopy (discussed below), a transtracheal biopsy (through the trachea or windpipe) or transbronchial biopsy (through a large airway past the trachea) may be performed.
- Bronchoscopy – during this procedure a long, lighted, flexible fiber optic tube is passed down the windpipe and into many smaller airways of the lungs to assess the delicate lining of the lungs for cancers. During a bronchoscopy, biopsies may be taken for later examination as well.
In order to assess the possible spread of cancer after a definitive diagnosis, a physician may perform an endobronchial ultrasound (which utilizes sound waves to look for masses or cancer spread around the large airways of the lungs) or endoscopic esophageal ultrasound (during which sound waves are used to assess cancer spread around the esophagus and areas of the lungs around the esophagus). Other methods, which are slightly more invasive, include a mediastinoscopy and mediastinotomy. During a mediastinoscopy, a small incision is made in the breast bone and a camera is passed down to look for cancer and suspicious lymph nodes in the area between the lungs. A mediastinotomy involves a slightly larger incision and allows more thorough investigation of lymph nodes deeper than those examined by mediastinoscopy. A step further is called a thorascopy, which is a surgery that allows visualization of the lungs and chest wall via a small camera inserted through the chest wall. If a larger incision is required, it may be termed a thoracotomy.