Diagnosis and Staging
A number of tests and diagnostic tools may be utilized to identify lung cancer and determine how advanced it is. Blood testing is routinely ordered as part of the workup and includes a complete blood count (CBC) and chemistry panel (includes several parameters such as liver and renal function tests and electrolytes) (O'Hanlon 2013).
Imaging. X-rays, magnetic resonance imaging (MRI), chest CT, and positron emission tomography (PET) scans are used in the diagnosis and staging of lung cancer (Horn 2013a). In addition, a bone scan may be performed to see if the cancer has moved into the bones (Horn 2013a; American Lung Association 2014b). PET scans can also help determine if cancer has metastasized to other areas of the body (Schrevens 2004). A PET scan involves injecting the patient with a radioactive tracer compound called fluorodeoxyglucose, or FDG, which is a modified glucose molecule that can still be taken up by cells. Shortly after being injected with FDG, the patient is analyzed with computer-aided scanning technology that detects gamma rays emitted by the radioactive FDG. Since cancer cells are more metabolically active than most normal cells, the FDG, which cells recognize simply as glucose, is taken up more rapidly into cancerous tissue. Thus, a PET scan will reveal areas of cancer metastasis by detecting higher concentrations of FDG in affected tissues (Lucignani 2004; Avril 2001; Huang 2000; Bustamante 1977; Lopez-Lazaro 2008; Verhagen 2004; Zhu 2011).
A tissue sample is necessary to accurately diagnose the type of lung cancer, plan treatment, and predict prognosis (O'Hanlon 2013).
Biopsy. Fine needle biopsy uses a long, thin needle to remove a piece of tissue from the lungs, which can then be examined under a microscope (American Lung Association 2014b). A biopsy may not be necessary if tissue will be obtained during surgery to remove the tumor (NCCN 2014a).
Tissue samples can be obtained several different ways. The type of procedure or biopsy performed depends on characteristics of the suspected cancer based on radiographic and clinical findings (Rivera 2013):
- Bronchoscopic biopsy. Bronchoscopy involves insertion of a flexible tube down the throat into the lungs to allow the physician to view the airways and lungs (A.D.A.M. 2013b). It is typically performed prior to surgery (NCCN 2014a).
- Endobronchial ultrasound (EBUS)-guided lung biopsy. Endobronchial ultrasound is similar to a bronchoscopy except an ultrasound device is fitted onto the end of the bronchoscope. It is used to see if the cancer has spread to the lymph nodes and/or nearby tissues in the chest (American Lung Association 2014b). Endobronchial ultrasound (EBUS)-guided lung biopsy is a minimally invasive procedure in which a thin catheter with a balloon at the end is inserted into the airways to obtain detailed images. A biopsy instrument can be inserted through the catheter to obtain a biopsy sample (Gomez 2009).
- Mediastinoscopy is performed by a surgeon inserting a small camera through tiny incisions to visualize the mediastinum (ie, the part of the chest between the sternum and spine and between the lungs). This procedure is useful for removing lymph nodes and looking for abnormal growth on the outside of the lungs and in the chest (A.D.A.M. 2012a; A.D.A.M. 2012b).
- Thoracoscopy, video-assisted thoracic surgery (VATS). A surgical procedure in which the surgeon looks for and removes tumors in the chest wall (American Lung Association 2014b).
Sputum cytology. Mucus coughed up from the lungs is examined under a microscope for any cancer cells (American Lung Association 2014b).
Thoracentesis. The doctor slips a needle between the ribs to drain fluid and assess it for cancer cells (American Lung Association 2014b).
The extent of the cancer is determined by tumor size, whether cancer cells have spread to nearby lymph nodes, and whether additional metastatic events have occurred. NSCLC is staged from I to IV, with stage IV representing advanced, metastatic cancer. Stages are further subdivided based on specific characteristics of the tumor and lung as well as where the cancer has spread (NCCN 2014a; NCI 2013a).
SCLC cases are divided into either a limited disease stage, in which the cancer is limited to the lungs and nearby lymph nodes, or extensive disease stage, in which metastasis to areas outside the chest cavity has already occurred (NCCN 2014b).
Staging is completed after several tests, including MRI, CT, or PET scans; bone scans; pulmonary function tests; endoscopic ultrasound; mediastinoscopy; lymph node biopsy; and sometimes, bone marrow aspiration and biopsy to see if the cancer has metastasized to the bone marrow (NCI 2013c).
Lung Cancer Screening
Most major lung- and cancer-related organizations, including the American College of Chest Physicians, American Society of Clinical Oncology, American Cancer Society, and American Association for Thoracic Surgery now recommend annual screening with low-dose computed tomography (LDCT) in current smokers and most former smokers ages 55 to 80 (depending on specific guidelines). Recent guidelines recommend screening with LDCT for current smokers who have smoked an average of a pack of cigarettes a day for 30 years or who have quit within the past 15 years after smoking at these levels (Moyer 2013).
The recommendations are based on the results of the National Lung Screening Trial, which were published in 2011. The study found that current or former heavy smokers who underwent 3 annual lung cancer screening examinations using LDCT had a 20% reduction in lung cancer mortality over the five- to seven-year duration of the study compared to those screened annually with chest X-rays (National Lung Screening Trial Research Team 2011). Additional evidence suggests LDCT may prevent approximately 12 000 lung cancer deaths per year in the United States (Ma 2013).
If the screening detects lung nodules, additional radiographic tests are conducted based on the size of the nodule, including a follow-up LDCT in 3 to 6 months or an immediate CT/PET scan. Patients with large nodules are referred to a surgeon for biopsy or surgical removal (NCCN 2014a).
LDCT scans do expose patients to some radiation; this exposure is lower than one year’s worth of background radiation (Detterbeck 2013). Nevertheless, potential risks due to radiation exposure are considered to be outweighed by the benefits of lung cancer screening with LDCT (UKCC 2014).
Researchers are working to identify blood tests that could be used to screen for lung cancer. A study published in the Journal of Clinical Oncology in early 2014 validated the use of a blood test that analyzes small fragments of genetic material (microRNA) in blood plasma to detect lung cancer up to two years earlier than spiral CT, with fewer false positives than the imaging test. The test looks for genetic markers of lung cancer; this test or one like it could enter the United States and European markets sometime in the near future (PR Newswire 2014; Sozzi 2014).