Patients should discuss early lung cancer screening issues with their personal physicians. Any patient who is at increased risk for developing lung cancer and is currently undergoing periodic screening chest X-RAYs should consider undergoing low-dose screening chest CT because of its superior ability to detect small pulmonary nodules. The high-risk patient group studied in the ELCAP study consisted of men and women over the age of 60 with at least 10 pack-years (one pack per day for 10 years).
The lung cancer screening exam must be performed on a spiral (helical) CT scanner. Spiral CT is more accurate than routine chest X-RAY in detecting tiny nodules, and compared to conventional non-spiral CT scanners, a spiral scanner can image the entire lung with minimal radiation using a single breathold.
The Low-Dose Spiral Screening CT is designed to replace the chest X-RAY in screening asymptomatic patients for pulmonary nodules. The low-dose technique is ideal to evaluate the lung parenchyma for nodules, but is not intended to screen for abnormalities elsewhere in the chest, such as the aorta, heart, lymph nodes, or bones. Like screening mammography, it is important to minimize the amount of radiation exposure in asymptomatic patients. No intravenous contrast is used. Like many other screening tests, many insurance companies will not pay for this exam, although in the future in high-risk patients this situation will hopefully change. The cost of a Low-Dose Screening CT exam is less than half of that for a Diagnostic Chest CT exam.
Diagnostic Spiral Chest CT scans are almost always performed to further evaluate an abnormal finding on chest X-RAY or to evaluate the chest in certain specific disease conditions. Unlike a low-dose screening exam, which evaluates only the lung parenchymal tissue, a diagnostic exam images all tissues in the chest (aorta, lymph nodes, airway, bones, etc.) and often requires intravenous contrast.
The radiation from a low-dose screening CT exam is very minimal and is approximately equal to that received from a standard chest X-RAY or from flying in a commercial jet across the country.
What does the procedure involve?
On the day of the exam after registering at the front desk, the patient will be asked to complete a brief lung cancer risk factor questionnaire. Then, the patient lies down on the Spiral CT scanner table and is positioned for the exam by the technologist. No intravenous line or contrast is needed. The patient holds his or her breath and the table will move through the gantry of the CT scanner while images of the lungs are taken. In approximately 20 seconds, the exam is complete.
What kind of results can be expected?
A “negative” result means that there are no nodules detected. Patients should discuss with their physician when they should return for a repeat exam. Although there is not uniform agreement on how often repeat screening CT should be performed, patients at high risk for lung cancer should consider undergoing this exam on a yearly basis. A “positive” result will be any patient with one or more pulmonary nodules. In this event, a patient may be asked to come back for a diagnostic CT chest exam, which examines all tissues in the chest, not just the lung parenchyma, and which may be performed with intravenous contrast. A diagnostic CT chest exam only takes slightly longer than a screening exam and is performed to confirm the results of the screening exam. In addition, additional thin slices may be taken of the nodule or nodules to determine the presence of calcium or fat, which is often seen in benign nodules. In addition, you may be given intravenous contrast material for your diagnostic CT scan, which may help distinguish a benign nodule from a malignant one. Just because a nodule is found does not mean that you have lung cancer. Depending on the results of the diagnostic spiral CT scan and after conferring with your personal physician, you may be referred to a lung specialist for bronchoscopically guided needle biopsy or to an interventional radiologist for percutaneous fine needle biopsy of your nodule. In many cases, when the nodule is too small to be biopsied, you may be asked to return in 3 or 6 months for another spiral CT scan that will precisely determine whether or not there is growth in the nodule.
