Lung Cancer Screening

The debate over lung cancer screening techniques requires some explanation. Survival rates appear to increase with early tumor detection, so it may seem reasonable to start treatment at the first sign of lung cancer. However, clinical trials have examined standard screening devices, including the chest x-ray, and have been unable to provide definitive evidence that early tumor detection extends patient life.

Critics have argued that current cancer screening often generates false positive results, mistaking a non-threatening condition for a tumor. This leads to further, more invasive testing, such a biopsy or thoracotomy (the surgical removal of lung tissue through a chest incision), procedures which carry their own health risks.

Ongoing clinical trials are examining the viability and effectiveness of various screening procedures, and how survival rates are affected by early tumor detection. The chest x-ray, computerized tomography and bronchoscopy are the tools at the heart of the ongoing cancer screening debate.

Does a Chest X-Ray Help?

The chest x-ray has long been considered the standard screening device for lung cancer: A chest x-ray is fast, non-invasive and relatively inexpensive. X-ray results can detect tumors as small as one to two centimeters (0.4 to 0.8 inch). Advocates of chest x-rays suggest that their use may improve survival by ten to twenty percent. However, the results of a joint twenty-year study performed by the National Cancer Institute and the Mayo Clinic suggest that routine chest x-rays do not significantly improve lung cancer survival rates.

Spiral Computerized Tomography

Spiral computerized topography (also known as a spiral CT scan), uses a rotating x-ray machine to take pictures of the lungs. These pictures are then compiled by computer to create a 3-dimensional image. Spiral computerized tomography can detect abnormalities in the lungs less than one centimeter (0.4 inch) in length. Clinical trials are comparing spiral CT scans to conventional chest x-rays, to see if they provide more effective cancer screening results and higher survival rates.

Fluorescent Bronchoscopy

During a bronchoscopy a lighted tube is inserted into the airways through the mouth, and relays pictures to a monitor. By using blue fluorescent light instead of regular white light, clinical trial investigators have been able to identify lesions less than one millimeter (0.04 inch) across. Investigators hope that fluorescent bronchoscopy will eventually be used routinely in high-risk individuals to detect the first signs of lung cancer, before symptoms develop.

Early Detection, False Positive Results and Over Diagnosis

The issue is not that cancer screening devices, such as CT scans and bronchoscopy, can detect small tumors. The debate centers on the number of false positive results that cause people anxiety and fear, and can lead to further unnecessary testing. Scaring from smoking, lung inflammation, and other respiratory conditions may be mistaken for early-stage tumors. An unneeded biopsy or thoracotomy can put the body through stress, can cause unwanted complications, and can aggravate existing heart conditions.

Over-diagnosis is another concern. Treatment is often given at the first sign of lung cancer, but critics argue that many small tumors may never become life threatening, and don’t actually require medical intervention.

The debate is complex. Do you start treatment at the first possible sign of lung cancer, whether treatment is necessary, or not? Are unnecessary treatments justified as preventive medicine? The argument over the validity of screening techniques is not likely to be resolved soon. In the meantime, staying informed of all your options is your best choice.

Resources

ClinicalTrials.gov. (reviewed 2003). Fluorescent light bronochoscopy plus white light bronchoscopy for early detection of lung cancer.

Reuters Health. (2003). Lung screens find cancer, but at high cost: Study.

Marcus, P.M., Bergstralh, E.J., Fagerstrom, R.M., Williams, D.E., Fontana, R., Taylor, W.F., Prorok, P.C. (2000, August 16). Lung cancer mortality in the Mayo Lung Project: Impact of extended follow-up. Journal of the National Cancer Institute, 92(16), 1308-1316.

National Cancer Institute. (2002). NLST: National lung screening trial.

Oncology News International. (1997, October). Florescent ‘LIFE’ images spot occult lung cancer lesions.

Shaw, G., Walsh, F., Rolfe, M., Cantor, A., Vick, V., Andra, K. (1999). Value of fluorescent bronchoscopy in identifying bronchial metaplasia and dysplasia in smokers. ASCO Annual Meeting Abstracts.