Lung Cancer

 For many years we had no good screening test for lung cancer.  Traditionally we relied upon chest x-rays (CXR) as the screening modality, but this turned out to be a poor choice. 

To qualify as a good screening test, the procedure must meet several criteria. First,  the condition must be prevalent enough in the population to allow  screening to be cost effective.  Lung cancer certainly meets this criteria.  A condition like adrenal cancer wouldn't qualify, as the disease isn't common enough to make a screening test worthwhile.  This of course is from a population point of view; for one afflicted with adrenal cancer, screening might have helped.  But the decisions are based on a value to the population, not an individual.

The second criteria is that the test must be easily assessable and acceptable to the patient. A CXR certainly meets this criteria.  A brain biopsy looking for Alzheimers disease would not. 

Third, the disease being screened for must have an effective treatment.  Lung cancer can be treated.  A disease such as ALS cannot be, and so there is no screening test -- what would you do with the information should a diagnosis be made?

Finally, the screening test must confer a mortality benefit for the patient.  For example, a screening colonoscopy significantly reduces the risk of death from colon cancer. Finding a polyp and removing it essentially prevents colon cancer. 

This last is what detracted from a CXR being used as a screening test.  The radiograph certainly can find a lung cancer in the pre-symptomatic stage, allowing earlier treatment, but this has not been shown to make much of a difference.  Waiting until a person becomes symptomatic before initiating treatment for lung cancer essentially results in the same outcome as diagnosing it earlier with a CXR.

However, the use of a CT scan to look for suspicious nodules, and allowing them to be surgically resected HAS been show to reduce death form lung cancer, and so meets the criteria for a good screening test. 

The group that most benefits from this CT scan, which is done yearly, are those with a 20 pack year smoking history.  A pack-year is the number of packs per day multiplied the number of years smoked (1 pack per day (PPD) for 20 years; 1/2 ppd for 40 years, etc.).  There is no longer a criterion, as there once was when the guideline was first developed, as to when one had stopped smoking, if relevant. 

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