Reducing Lung Cancer Death Rates: Low Dose Helical CT Scans

Lung cancer is the leading cause of cancer death among men and women. The American Cancer Society predicted that approximately 219,000 new cases of lung cancer would be diagnosed in the U.S. in 2009--causing about 159,000 deaths. Now there's some good news about reducing the number of deaths from lung cancer, thanks to thanks to the findings with a helical or spiral CT scan.

Standard chest x-ray versus helical CT scan

A study sponsored by the National Institutes of Health (NIH) enrolled more than 53,000 former or present heavy smokers (they smoked at least one pack a day for 30 years). Participants were 55 to 74 years of age with no evidence or history of lung cancer at the time the study was started in August 2002. They were randomly assigned to three annual screens with either helical CT or chest x-ray. Results were so good that the study was stopped in October 2010. That's when preliminary results showed that those who underwent CT scans had a 20.3 percent reduction in lung cancer death rate compared with those who had standard chest x-rays.

Why the CT scan makes a difference

An important reason for the high mortality of lung cancer is that it can’t be treated effectively in about three out of four afflicted people because they don’t present with symptoms until the cancer has advanced too far locally or has spread to other parts of the body. The overall average five-year survival rate for people diagnosed with lung cancer is only about 16 percent, BUT the survival rate is much greater when the cancer is detected and treated  early.

Many studies have looked for tests that would detect lung cancer early enough to improve survival. The most obvious approach was repeatedly screening high risk individuals with chest x-rays. Although chest x-rays twice a year did pick up more early cancers, screening did not reduce lung cancer death rate even when examination of sputum for malignant cells was added. So, the findings with spiral CT are quite exciting because no other screening procedure has reduced lung cancer death rates.  

Downsides to regular CT scans

It is premature for any official recommendations regarding spiral CT scanning, in part because the data from the study have not been fully examined or undergone peer review.  In addition, some of the potential downsides to regular CT exams include the following:

• False positive results (possible cancer lesions which turn out to be benign) were present in about 25 percent of subjects screened with CT.  False positives lead to further costly and possibly interventive tests like biopsies.
• High radiation exposure.  X-ray doses were about 15 times higher for spiral CT than for conventional chest x-ray, but somewhat lower than the exposure for a mammogram.
• False negatives (missing the presence of a malignant tumor) can lead to unwarranted reassurance.

After further examination of the study findings, and despite these potential harms of spiral CT scans, it seems likely that this screening procedure will be recommended for asymptomatic, high risk people. An approximate cost of $300 per scan is not unreasonable for possibly preventing death from lung cancer.

The best advantage is prevention

It must be kept in mind, however, that any possible advantage of early detection of lung cancer is far outweighed by the benefits of preventing lung cancer in the first place by not smoking. It is estimated that cigarette smoking is the cause of more than 90 percent of lung cancers.