Cancer Screening Using Low-Dose CT
What is Cancer Screening?
Screening is the use of tests or examinations to detect a disease in people without symptoms of that disease. For example, the Pap test is used for cervical cancer screening. Screening for some cancers is important because it can help the doctor discover cancer early and treat it successfully. Because lung cancer usually spreads beyond the lungs before causing any symptoms, an effective screening program for early detection of lung cancer has the potential to save many lives.
The use of chest X-rays was evaluated several decades ago. Most studies concluded that these tests could not find many lung cancers early enough to improve a patient’s chance for a cure. For this reason, lung cancer screening is not a routine practice for the general public or even for people at increased risk, such as smokers.
Recently, a new technique of X-ray called spiral or helical low-dose computerized tomography (CT) scanning has been successful in detecting early lung cancers in smokers and former smokers. Because this technology may be useful for high risk populations, the Worker Health Protection Program is offering this lung cancer screening to former workers from Mound, Fernald, INL, NTS and to both current and former workers from Y-12, ORNL and the GDPs, aged 50 to 85 who have a history of smoking and/or occupational exposure to known lung cancer risk factors, such as asbestos, radiation and beryllium. Workers aged 45 to 85 are also eligible if the medical screening results show asbestos-related findings on the chest X-ray or an abnormal beryllium lymphocyte proliferation test (Be LPT).
Why is Screening for Lung Cancer
in a High-risk Population so Important?
Lung cancer is the leading cause of cancer death for both men and women. About 160,000 people in the United States will die of lung cancer each year. Without screening, over 50 percent of lung cancers are found at a late stage and the overall five-year survival rate for lung cancer is currently 15percent, meaning only 15 of every 100 people survive at least five years. By contrast, if lung cancer is found early and treated by surgery, before it has spread to lymph nodes or other organs, the five-year survival rate increases dramatically – as high as 70%. This means that 70 out of 100 of these patients are likely to survive for at least five years.
Several studies have shown that low-dose CT screening detects many lung tumors at early stages. For example, in a study done of 1000 smokers and former smokers, low-dose chest CT found 27 tumors while conventional chest X-ray found only 7. Of the 27 tumors the CT scan identified, 23 (85%) were in the early stages. The X-rays only found four of these early tumors. (Lancet 1999; 354: 99-105.)
In addition, in June 2011, the National Cancer Institute (NCI) released results from its National Lung Screening Trial (NLST) that showed a 20 percent reduction in deaths from lung cancer among current and former smokers who underwent three successive, annual low-dose chest CT screenings, compared to a similar group (the “control group”) who underwent chest X-ray screenings.
What is Spiral, Low-dose CT?
Low-dose spiral CT is a simple procedure in which a special imaging machine rotates rapidly around the body taking over 100 pictures in sequence. This information is processed by a computer to produce a cross-section of a specific area. The low-dose CT scan uses less radiation than a standard CT and yet is sensitive enough to detect abnormalities that are too small to be seen on a conventional set of chest X-rays.
How is the Low-dose CT Procedure Done?
Throughout the low-dose CT scanning procedure, the patient lies very still on a table. The patient passes through the x-ray machine, which is shaped like a doughnut with a large hole. The machine rotates around the patient and a computer creates images from the scan that can be reconstructed into a 3-dimensional model of the lungs. When the picture is taken you will be asked to hold your breath for approximately 10 seconds. The amount of radiation (an estimated average of 1.2 mSv or 120 mrem for most people) is significantly less than that absorbed during a diagnostic CT scan of the chest (an estimated average of 8 mSv or 800 mrem). As further comparison, the estimated average annual exposure from natural sources in soil and air is 3.1 mSv or 310 mrem per year.
What Will Happen if the CT Scan Shows an Abnormality in My Lung?
If an abnormality is detected on the CT scan, it may or may not be cancer. If there is suspicion of a lung cancer, you will be notified within 10 working days of the screening. At that time, we will advise you to see your personal physician, who may recommend, diagnostic testing. We do not pay for any such diagnostic testing or any treatment that may follow. Those expenses are normally covered by health insurance, including Medicaid and Medicare. Sometimes the doctor will be able to tell from the CT scan that the lung nodule is not cancerous. In this case, or if the CT scan shows no nodule at all, you will be notified within 3 weeks of the screening and no follow-up will be needed.