Lung Cancer

Methods for Diagnosing and Staging

Several tests are available to help your doctors learn more about your lung cancer. These tests serve two important purposes. First, they provide details that help your doctors make a specific diagnosis about the type of lung cancer you have. Second, the tests offer information that are factors in assigning a stage to the lung cancer. An accurate diagnosis and stage are vital elements for determining the best treatment options, which may spare you from treatment that is not likely to be effective.

You may not need to have every diagnostic imaging study, and usually only one type of staging procedure is done. Your doctors will consider the results of your physical examination and your general health status in deciding which tests will provide the most useful information. Learn how these tests are done and what you can expect (Table 1), and ask your doctor any additional questions you may have.

Table 1: Diagnostic and Staging Procedures: What to Expect

Diagnostic Imaging Studies

Imaging studies are primarily used to help define the size, shape and location of the tumor. They are also useful in assessing other parts of the body to see if the lung cancer has metastasized (spread beyond the lung), which aids in defining the stage of disease.

Chest X-ray

Standard chest x-rays are often the first type of imaging study done because of their convenience and low cost. A chest x-ray is usually the first imaging study to show an area on the lung that is suspected to be cancer.

Computerized Tomography (CT)

CT produces three-dimensional, cross-sectional x-ray images, so it can provide more precise details than a standard x-ray. CT scans provide an excellent assessment of the size of lymph nodes, but the size does not always indicate whether or not the nodes are involved with cancer. Thus, other studies to evaluate the lymph nodes may be done.

Spiral CT

Spiral CT is being used in an increasing number of medical centers to screen for early lung cancers. Spiral CT (also known as helical CT) offers many advantages compared with standard CT. For example, the machine used for spiral CT is faster, which allows for many images to be made during one breath-hold. In addition, the images produced by spiral CT are more detailed because the image slices are thinner and because motion artifact (distortion of the image caused by motion) is eliminated by completing the scan in one breath-hold. As noted earlier, individuals who are at high risk of lung cancer should discuss a screening spiral CT scan with their doctor. When spiral CT is done, any abnormality found should be evaluated by doctors at a center specializing in the evaluation of abnormal CT scans.

Positron Emission Tomography (PET)

PET scans do not yield images that are as finely detailed as a CT scan, but they can provide helpful information, especially if you have early stage lung cancer, because the scan may show that the cancer has spread to other sites. PET scans are particularly useful if your doctor thinks cancer may have spread beyond the lung but does not know where. PET scans are also helpful in distinguishing cancerous lesions from benign (noncancerous) lesions. PET scans are not helpful for finding metastasis to the brain; rather, magnetic resonance imaging (MRI) of the brain is done to determine whether cancer has spread to the brain.

CT/PET

In diagnosing lung cancer, PET scans are most often used in combination with a CT scan, with the two tests done in the same testing session. The use of both tests provides a more complete picture for the radiologist, who can compare areas of higher radioactivity on the PET scan with the detailed appearance of the same area on the CT scan.

MRI

MRI may also be done to look for metastasis in other parts of the body and is most valuable for detecting metastasis in the brain or spinal cord. A brain MRI is commonly done in the initial staging of lung cancer.

Bone Scan

A bone scan is done to determine whether lung cancer has spread to bone. A bone scan is often not needed because PET scans, which are more commonly done for people with lung cancer, can also show if cancer has spread to bone. A bone scan is usually done only if a person has signs and symptoms of metastasis.

Staging Procedures

Staging procedures allow the doctor to view the lungs and/or surrounding area directly and to obtain a biopsy sample from the tumor and/or nearby lymph nodes or other tissue.

Bronchoscopy

A bronchoscopy allows your doctor to look inside the lungs and bronchi (large airways in the lung) for abnormal areas. Tiny tools can be inserted into the bronchoscope to obtain samples of tissue or fluid.

Endobronchial Ultrasound

Endobronchial ultrasound is a newer technique that offers a way to view the mediastinal area without the need for incisions, as it is done using a bronchoscopy. The images provided by the ultrasound instrument help guide the doctor in obtaining samples for evaluation. This procedure also allows the doctor to stage the mediastinal lymph nodes. The tissue samples obtained with this technique are smaller, and this can be a problem if there is not enough tissue to test for genetic alterations, which may be important for selecting appropriate treatment.

Mediastinoscopy

Mediastinoscopy is considered to be the best method for evaluating lymph nodes in the mediastinum (the area of the chest between the lungs and the heart). The doctor can remove lymph nodes through small incisions (surgical cuts) made just above the breastbone or on the left side of the chest next to the breastbone. It is essential to stage the mediastinal lymph nodes — that is, determine if cancer has spread to these nodes — when they appear enlarged on CT scans or have high areas of radioactivity on a PET scan. Mediastinal staging is important because a small tumor may appear to be early stage disease, but if the mediastinal lymph nodes are involved with cancer, the cancer is actually a later stage, which means the treatment approach should be different. You should talk to your doctors about whether a mediastinoscopy or endobronchial ultrasound is the best procedure for you.

Evaluation of Tissue Samples

Samples of tissue obtained during these procedures are examined by a pathologist, a doctor who specializes in the microscopic examination of tissues for cancer (and other diseases), to see if cancer cells are present and, if so, to determine what kind of cancer the cells represent (the histologic type). The pathologist will also document the size and location of the tumor, the number of lymph nodes with cancer cells and other important facts about the cancer. In some instances, the pathologist may not be able to identify the histologic type because the tissue sample is too small. When this happens, another biopsy may be necessary. The pathologic evaluation of biopsy samples offers the most valuable information for the diagnosing and staging of lung cancer.

Testing for Genetic Mutations

As researchers learn more about the biology of lung cancer, they have discovered three genetic mutations (alterations) that may affect how non-small cell lung cancers grow and, perhaps more importantly, how they respond to some types of treatment. These three mutations are mutually exclusively; that is, none is found with another in the same tumor. The genetic mutations differ according to the types of people and lung cancers in which they are most often found (Table 2).

Determining whether any of the three genetic mutations is present is becoming an important part of diagnosis of non-small cell lung cancer, especially among people with advanced disease, as their presence or absence can influence treatment choices. Talk to your doctor about whether your tumor specimen should be tested for genetic mutations, which is also known as molecular testing.

Table 2: Genetic Mutations in Non-Small Cell Lung Cancer

Additional Sources of Information

• American College of Chest Physicians: www.chestnet.org
    Living with Lung Cancer: Patient Education Guide
• College of American Pathologists: www.mybiopsy.org
• Lung Cancer Online: www.lungcanceronline.org
    Tests and Procedures
• National Cancer Institute: www.cancer.gov
    Non-Small Cell Lung Cancer Treatment (PDQ®)