As the CT scan became more popularly available, people tried to expand its use from a diagnostic tool to a screening tool. The use of CT scans in screening smokers for lung cancer became particularly controversial. Since 85 percent of all lung cancers are found in smokers and another 5 percent in persons exposed to secondhand smoke, many in the academic community argued that routine screening of smokers would have the salutary effect of identifying early stage lung cancers. Others in the medical community, such as the Mayo Clinic, urge caution.
CT Scans
CT, or computerized tomography, scans are important tools that provides three-dimensional cross section images of the body. Conventional x-ray imaging results in a two-dimensional low resolution image of hard tissue. CT scans provide exquisite depth and high resolution images of soft tissue because they are generated using multiple x-rays from different angles. Consequently, they are capable of picking up tiny lung nodules that are not apparent using conventional techniques.
Lung Cancer
According to the National Cancer Institute, lung cancer is the leading cause of cancer-related death in the United States. Roughly 90 percent of all lung cancer cases can be attributed to smoking. Unfortunately, lung cancer is invariably diagnosed late, so the five-year survival rate is only 14 percent.
Since smoking and cancer are so intertwined and diagnosis was made late, smokers were seen as an ideal population to screen for lung cancer. The hope was that early diagnosis would lead to prompt treatment, reduced mortality and longer survival rates.
Pros
Columbia University College of Physicians and Surgeons suggests that screening CT scans in high-risk individuals such as smokers are highly advisable because CT scans detect 2 and 3 millimeter nodules in the lungs that cannot be detected with chest x-rays.
An October, 2006 issue of the New England Journal of Medicine includes a study in which 31,567 asymptomatic smokers received CT scans. In the study, 412 people with early stage I cancers were identified, 302 of which underwent surgery to remove the tumor. The estimated 10-year survival rate of this group is 88 percent which is far higher than if those tumors were diagnosed later.
Cons
Despite these results, the Mayo Clinic and the National Cancer Institute do not support screening at this time. They point to the risk of unnecessary surgery and exposure to radiation. The National Cancer Institute notes that improved long-term survival rates engendered by early treatment do not necessary equate to reduced mortality. In addition, many of the nodules found in the lungs of smokers are not cancerous at all.
Future Research
As of 2010, The National Cancer Institute is conducting a long-term study entitled the "Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial." This study examines the long-term benefit of CT scans as a screening tool for lung cancer. By tracking patients who were diagnosed early and treated promptly, the organization hopes to determine whether overall mortality is improved.
References
- National Cancer Institute: Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial
- National Cancer Institute: Spiral CT Scans for Lung Cancer Screening: Fact Sheet
- Columbia University Dept of Surgery: Lung Cancer, Screening & Early Detection
- Mayo Clinic: Lung CT scan for cancer: Should you be screened?
- New England Journal of Medicine: Survival of Patients with Stage I Lung Cancer Detected on CT Screening
