 
Exams may be scheduled at
619-849-XRAY (9729).Please contact
Dr. Mark Schechter
if you have any questions or comments at
(619) 849-XRAY (9729)
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Early Lung Cancer Screening:
Detection By Low-Dose Multislice Spiral Chest CT
Why is there a need for improved lung cancer detection?
There were an estimated 160,000 deaths from lung cancer in the United States in 1998 with an estimated 172,000 new cases diagnosed. Despite understanding that the main risk factor, tobacco, is known for the development of lung cancer, the prognosis for the disease remains dismal. The overall cure rate of lung cancer is approximately 12%, but the cure rate for Stage I cancers is 70-80%. Any lung cancer screening method that can safely detect a large number of potentially curable Stage I lung cancers is an exciting public health development.
What methods are available for the detection of early lung cancer?
Screening protocols based on chest x-rays and sputum cytology are relatively insensitive in the detection of small, potentially curable Stage 1 lung cancers. Computed Tomography (CT) is unequivocally more sensitive than chest x-ray in detecting small potentially curable lung cancers and other kinds of parenchymal lung disease.
What scientific studies have been done to evaluate this test?
Until recently, most scientific studies examining lung cancer screening documented negative results. Although poor design and other flaws probably beset these studies conducted in the 1970’s, they were performed before computed tomography (CT) became widely available in the 1980’s.
In the July 1999 Lancet, there was published a landmark scientific study (Early Lung Cancer Action Project or ELCAP) which demonstrated that CT can greatly improve the likelihood of discovering small potentially curable Stage 1 lung cancers in a high-risk patient group (heavy tobacco users) when compared to chest x-ray. In this study, CT detected three times as many non-calcified pulmonary nodules as chest x-ray in the study group and CT detected six times as many Stage I cancers as chest x-rays. In addition, the malignant nodules detected on CT were significantly smaller than those detected on chest x-ray. This is very important because the smaller the tumor size the more likely it is a curable Stage 1 cancer. Indeed, approximately 70-80% of Stage 1 lung cancers are curable, compared to an overall 12% cure rate for all lung cancers.
In the ELCAP patient group, non-calcified pulmonary nodules were detected in 23% of the screening CT exams compared to only 7% of the chest x-rays performed in the same patients. Malignant disease was detected in 2.7% by CT scanning and in only 0.7% by chest x-rays. Stage 1 cancers were detected in 2.3% by CT and 0.4% by chest x-ray. Further studies are necessary to confirm the cure rate of Stage I cancers identified by this method and compare it to other available survival data, to further refine low-dose screening CT recommendations in high-risk patients, and to document the cost-effectiveness of this method.
Who should consider undergoing lung cancer screening?
Patients should discuss this issue 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).
What type of machine is required to perform this test?
This 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.
How is Low-Dose Screening CT different from Diagnostic Chest CT?
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.
How much radiation does a patient receive from a Low-Dose Screening CT exam?
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.
Why should patients have their Low-Dose Screening CT exams at Radiology Medical Group?
Radiology Medical Group, Inc. - The leaders in medical imaging services since 1917! The radiology physicians and staff of RMG are nationally recognized for their leadership, imaging expertise, and innovation for over 80 years in the San Diego medical community. Screening CT chest examinations and other diagnostic CT studies are performed on our new Multi-Slice CT (MSCT) scanner, which represents the latest and most advanced spiral CT technology. Compared to conventional single slice or dual slice spiral CT, MSCT offers improved image quality and exam speed. As with all examinations performed at RMG, medical images and results are immediately and electronically available to your physician.
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