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Lung screening is a noninvasive, painless procedure that uses low-dose x-rays to screen the lungs for cancer in just 30 seconds. Lung screening is performed on a multislice computed tomography (CT) scanner and can detect smaller nodules or cancer than standard chest x-rays. A tumor or nodule is a mass of extra cells that grows on the lungs. It can be benign (noncancerous) or malignant (cancerous). By detecting malignant tumors in an early stage with CT lung screening, intervention can occur at a time when the cancer is still curable and localized to the lungs.

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Why is lung screening important?

Lung cancer is the number one cause of cancer-related deaths in the United States. This disease is responsible for more deaths annually than breast, prostate, and colorectal cancers combined. Over 169,000 new cases of lung cancer will be diagnosed this year. In 2002, lung cancer is expected to kill 154,900 people (89,200 men and 65,700 women). In the United States, the lifetime risk of developing invasive lung cancer is 1 in 17 for men and 1 in 18 for women. In Delaware, 500 people will die of lung cancer and 600 new cases will be found this year. These rates are above the national average for both men and women.

It is estimated that as many as 80% of lung cancers could be cured if detected at an early stage. Unfortunately, only 15% of lung cancers are caught at this stage, making the 5-year survival rate for all stages of lung cancer 20%. Catching lung cancer in an early stage while it is still localized to the lungs is essential. A person’s chance of survival decreases when the tumor grows to be 3 cm or more. If the cancer spreads to areas of the body outside the lungs, the survival rate is only 3%, compared with 48% if the cancer is just in the lungs. CT lung screening is extremely capable of detecting lung nodules as small as 2 or 3 cm. By catching malignant tumors when they are still small, they can be removed before disease spreads to other areas of the body.

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Who should have lung screening?

Lung screening is recommended for individuals between ages 50 and 80 who have any of the following risk factors:

•  History of lung cancer
• 10 pack-year or more smoking history (1 pack of cigarettes per day for 10 years, 2 packs of cigarettes per day for 5 years, etc.)*
• Past history of smoking (less than 10 years ago)
• Repeated exposure to secondhand smoke
• Exposure to other cancer-causing agents (eg, asbestos and radon)

Follow-up screening is recommended every 1 to 2 years for patients who remain at high risk. It is important for patients to be aware that having a negative scan (no nodules or cancer) does not mean that lung cancer will not develop in the future if they remain at high risk for the disease.

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How accurate is lung screening?

Recent studies show that CT lung screening is more sensitive than standard lung screening methods (ie, chest x-ray, sputum cytology) in detecting lung cancer. Unlike standard chest x-rays, CT lung screening takes cross-sectional images of the lungs. This allows the radiologist to see the lungs from top to bottom. Chest x-rays only show views of the lungs from the front and sides. With 3D imaging, CT lung screening can measure the growth of tumors in all directions whereas standard x-rays can only measure tumors at their widest point, preventing the radiologist from tracking changes in the volume of the tumor.

Since 1993, the Early Lung Cancer Action Project (ELCAP) has been studying the ability of CT lung screening to detect small, stage I lung cancer. Participants in the study included 1000 men and women over age 60 with a 10 pack-year smoking history, no history of cancer, and no symptoms of lung cancer. Lung screening with low-dose CT detected positive findings in 233 participants compared with only 68 positive findings on standard chest x-rays. Overall, CT screening found a greater number of smaller nodules and nearly 6 times more stage I lung cancers than standard x-rays. CT lung screening found 20 cancers that standard chest x-rays did not detect. Of these malignant tumors, 85% were stage I cancers. ELCAP researchers estimated that this rate of early detection could increase the 5-year survival rate from 15% to between 60% and 80%. Another group of researchers studied the value of annual CT lung screening for detecting lung cancer and reported that screening CT correctly identified cancerous tumors 97% of the time.

In 2001, ELCAP reported results from repeat CT lung screenings. Researchers found that out of 8 individuals who had further nodular growth and underwent biopsy, malignancy was diagnosed in 7. It was concluded that the false-positives (nodules mistakenly identified as malignant) are uncommon and that screening identified disease at an earlier, more-curable stage.

A 2002 study by the Mayo Clinic found that CT lung screening is also superior to sputum cytology in detecting lung cancers. Out of 1520 participants, CT screening detected 23 of 25 cases of lung cancer whereas sputum cytology only found 2 cases. Out of these cancers, 57% were in an early stage of development.

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What are the limitations of lung screening?

As with all screening studies, false positives do occur with lung screening. False positives are findings that the radiologist interprets as a possible cancer when it is not. False positives can result in the removal of benign nodules and additional anxiety, medical expenses, and risk of an invasive procedure for the patient. In the ELCAP study, approximately 20% of participants had positive findings that were not malignant. A 2002 study by the Mayo clinic reported that out of 22 patients who had tumors removed, 7 (31%) were not cancerous.

ELCAP researchers suggest that false positives can be easily eliminated if physicians use a baseline CT scan to track the growth of tumors on follow-up screenings. This way only tumors showing growth typical of cancer undergo biopsy or surgical removal. For example, in the ELCAP study, small tumors that did not appear benign were followed for up to 24 months. Nodules were removed only if they showed growth or were more than 10 mm. In 2001, the ELCAP study released their latest results for repeat CT screenings. A total of 1184 repeat lung screenings were performed. Of these 1184 scans, positive results occurred in 2.5% of the participants. After monitoring growth of the new nodules, 8 participants underwent biopsy for suspicious nodules. Malignancy was found in 7 of the 8 nodules. The researchers concluded that false positive results found on biopsy are uncommon and catching lung cancer at an early, curable stage is far more beneficial than no screening at all.

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How does lung screening work?

Lung screening at Diagnostic Imaging Associates is performed on the multislice GE LightSpeed Plus or LightSpeed¹⁶ CT scanner. A CT scanner is a tool which allows the radiologist to see any nodules or lesions on the lungs. A volumetric data set is acquired and a digital picture is made by a computer after low-dose x-rays record multiple slices or cross sections of the body. The word “slice” is often used to explain the images taken of patient anatomy because they are similar to a single slice of bread taken from a whole loaf (Figure 1).

Figure 1. As with a loaf of bread that is cut into many slices, computed tomography can make pictures of “slices” of the body’s internal structures.

During lung screening, the patient is asked to lie on the table of the CT scanner. This tabletop moves the patient’s body through the opening of the CT scanner (Figure 2) which houses an x-ray tube and multiple rows of detectors. The x-ray tube rotates around the patient as x-rays pass through the body to the detectors, where thousands of x-ray measurements are received. Next, the computer processes this information and displays the corresponding images on a computer screen. This imaging technique avoids any overlap of organs or tissues.

Figure 2.

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What kind of preparation is involved?

No preparation is required for lung screening.

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What can I expect when I arrive for my lung screening study?

When you arrive at Diagnostic Imaging Associates for lung screening, you will be greeted by our staff at the front desk and escorted to a private waiting room. At this time, our Virtual Screening Manager will conduct a personal interview with you that will include questions about your family medical history and risk factors you may have for lung cancer.

Next, you will be taken to a dressing room and asked to change into an examination gown. You will then be lead to the CT suite where a radiologic technologist will position you on the table of our multislice GE scanner. Scout views will be taken to locate the lungs within your chest. During these scout views the technologist will enter your patient information (ie, name, patient number, examination date) into the computer workstation. The scout views will then be used to plot the slices of the lungs that will be recorded by the CT scanner. The next scan will obtain the slices that will be used to detect the presence of nodules or cancer. You will be asked to hold your breath for approximately 30 seconds during this scan. Holding your breath is very important because it eliminates blurring of the image that is caused by motion of the chest during breathing. Approximately 240 images of your lungs will be taken at this time.

After the images of your lungs are taken, you will be escorted back to the dressing room to change into your regular clothing. The results of your lung screening study will be mailed to you in three working days. Your report will include a summary of the radiologist’s findings and recommendations for further follow-up. Results will also be sent to your primary care physician, upon request. Because of the volume of images that must be analyzed, immediate results from the radiologist are not possible. Three working days allows the radiologist to take the proper amount of time to review your study and report accurate findings and, if necessary, to seek consultation with other physicians regarding any unusual findings.

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What do lung screening images look like?

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What if my lung screening study is positive?

If the radiologist notes that you have a positive finding on your lung scan, you will be advised to make an appointment to see your primary care physician and possibly a lung specialist to review the results and implications of your scan. You will likely undergo a diagnostic test to confirm the findings of your lung screening examination. A diagnostic CT scan uses the standard amount of radiation and produces images with higher resolution. This additional testing may show that the nodules are benign or are actually scars. If the nodules are suspicious, they will need to be followed or surgically removed.

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Is lung screening safe?

Each year the population of the United States is exposed to radiation from various background sources. The average dose of background radiation for a U.S. citizen living at sea level is 360 millirem (mrem). By comparison, a chest x-ray is 3.2 mrem, a mammogram is 17 mrem, and a barium enema is 540 mrem. The amount of radiation a patient receives from lung screening has been estimated to be around 100 mrem. Evidence has shown that a radiation dose of 100 rem (100,000 mrem) or more can cause irreparable cell damage.

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How much does lung screening cost?

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Where can I have a lung screening examination?

Diagnostic Imaging Associates is the first radiology provider in Delaware to offer Virtual Check-Up™ and requires no referral from a doctor or insurance plan. All virtual screening studies can be performed at three of our seven convenient locations – Omega Imaging & MRI, Brandywine , and Glasgow.

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