Wednesday, January 29, 2014

What Role Does CT Play in Screening for Lung Cancer?

The short answer is: depends

In December 2013, the United States Preventive Services Task Force (USPSTF) released a conditional recommendation for lung cancer screening. The Grade B recommendation states:
The USPSTF recommends annual screening for lung cancer with low-dose computed tomography in adults ages 55 to 80 years who have a 30 pack-year smoking history and currently smoke or have quit within the past 15 years. Screening should be discontinued once a person has not smoked for 15 years or develops a health problem that substantially limits life expectancy or the ability or willingness to have curative lung surgery.

For more information about what this means from a radiology perspective, here is an interview from ARRS InPractice:
Why did the USPSTF come to these conclusions?
Lung cancer is a serious public health problem, causing one in four cancer deaths. It is estimated that seven percent of people born today will develop lung cancer in their lifetimes. Eighty-five percent of lung cancer is caused by smoking; 85 percent of lung cancer is fatal. 
The randomized, multicenter, National Lung Screening Trial (NLST) trial [1], which compared three annual LDCT scans with three annual posterior-anterior chest radiographs at 33 sites in the United States, found that LDCT screening correlated with significant reductions in lung cancer (20%) and all-cause (6.7%) mortality.

Is CT the best method for lung cancer screening?
The NLST trial showed such a major advantage for LDCT over radiography for lung cancer screening —a 20% reduction in lung cancer mortality—that the trial was stopped early. Thus, CT is currently the only available examination for effective lung cancer screening.

How low can the patient radiation exposure be reduced for effective lung cancer screening?
In published trials [2], estimated radiation doses using LDCT have been between 0.60 and 1.75 mSv per exam. It is predictable that satisfactory LDCT results can be achieved with submSv doses, equivalent to less than 4 months of ambient radiation (assuming the natural occurrence of 3 mSv per year).

Check out InPractice for the rest of the interview with Dr. Patrick Colletti.  The USPSTF Statement wording is interesting - if screening is conditional on 'willingness to have curative lung surgery', should providers have a discussion with patients about treatment options if cancer is discovered prior to screening? Does this extend to other screening modalities such as mammograms? As the latter experience has shown, screening is not always benign. Hopefully future recommendations further clarify when and for whom screening should be undertaken. The real question now is: will insurance companies reimburse for lung cancer screening scans?