Lung cancer is the most common cause of cancer death in both men and women and is the only major cancer that screening is not recommended (e.g., breast, prostate, cervical, colon).
Screening for Lung Cancer
In the US, 25% of the population smokes. The lifetime risk of developing lung cancer in smokers is approximately 10%. More than 170,000 new patients are diagnosed each year with lung cancer. The 5-year survival is 13%, a figure which hasn't changed in decades.
Routine screening for lung cancer with chest radiography or sputum cytology in asymptomatic persons has been abandoned because the yield of chest x-ray screening is low (0.4% cancer). Prospective trials have shown no evidence that screening reduces mortality. Public health has emphasized the prevention of tobacco use.
Chest x-ray screening
The sensitivity of chest radiographs for Stage I disease is low (15%), data extracted from the NCI sponsored trials at the Mayo Clinic, Johns Hopkins, and Memorial Sloan Kettering institutions. In addition, of those lung cancers detected in those trials, up to 50% were interval cancers, or cancers that were diagnosed between the screening examinations.
Nonrandomized trials have shown that CT may be useful in lung cancer screening. CT nearly doubles the percentage with Stage I disease. The size of the detected cancers (average 15 mm) is half the average size detected on chest radiographs. While 5 year survival is increased in those that are screened, these results may not decrease mortality from this disease. A decrease in mortality can only be shown by a randomized trial.
CT Cost - Multiple CT examinations
CT screening is costly. Depending on the geographic locale, up to 60% of screened individuals may have a nodule which may be malignant. Determining whether such nodules are malignant requires multiple CT examinations over several months to make sure that the nodule does not grow. (See protocol below) Given the number of smokers and former smokers in the US, the cost may exceed $70 Billion dollars.
An NCI sponsored trial, coordinated by ACRIN, began September 2000. This is the most costly screening trial ever. ($200 million). It will be over 10 years before results are known. In the meantime, many patients are willing to undergo screening, in the hopes that screening will be of benefit.
Berlin L. Liability of performing CT screening for coronary artery disease and lung cancer. AJR 2002; 179:837-42. [Related Records]
|Collimation||5 mm||7 mm|
|Recons||3.5 mm||3.5 mm|
|Tube||40 mA||80 mA|
Dose 0..65 mRem compared to 5.8 mRem conventional CT
Time to Follow-up (from Kostis)
*motion artifacts increase the follow-up by 2-3 months
Bibliography: MedLine search for CT Screening for Lung Cancer