USPSTF Recommendations: Lung Cancer Screening

So, guideline season is still upon us, and I wanted to bring up something that kind of flew under the radar: Lung Cancer Screening.

You may remember a paper (and GR at UAB) from a few years ago that showed a mortality benefit for low dose CT scanning in smokers. The National Lung Screening Trial (NLST) This is the main study that drove the USPSTF to recommend CT screening in many smokers.

The guidelines are here. Here’s the scoop:

55-80 year olds with at least a 30pack year smoking history, currently smoking or quit within the last 15 years should receive Annual low dose chest CT. As with most screening guidelines, stop when life expectancy is “substantially limited” by another health problem, or when patients have been smoke free for more than 15 years.  Based on the wording above, it seems reasonable to stop at 80, sooner if there are significant comorbidities. They give this a Grade B recommendation.

Interestingly, the guidelines vary somewhat from the study itself.  The NLST enrolled patients 55-74, yet the guidelines recommend screening through age 80.  The study utilized 3 annual CT scans, and mortality benefit was seen after just those three scans. USPSTF recommended annual screening from 55-80 (potentially 25 scans if you start at 55 and the patient keeps smoking without developing some other health problem).

So the benefit of screening is obvious patients live longer, less likely to die from lung cancer.  The NLST enrolled >50,000 patients, screened them for 3 years, and then followed for an average of 6.5 years.  Overall mortality was reduced by 6.7% and lung cancer specific mortality was reduced by 20%.  NNS to prevent one lung cancer death is 320. In comparison, annual FOBT testing reduces colon cancer mortality by 15-20%, and the NNS 1173.

What about the harms?  Well, 39% of those in the CT group of the NLST had a positive test, and the majority of those led to more testing.  More testing may be more imaging, or may be a biopsy.  96% of the positive tests in the CT group were eventually proven to be false positives.  1.5% of those with a positive test had at least one complication from further testing.

Is this practice changing?  Maybe.  I have tried to order a low dose CT on a patient in the last few years, heavy smoker who I felt was high risk.  His insurance wouldn’t pay for it, but did pay for the regular CT when I told them I was worried about his weight loss.  The affordable care act mandates that all grade A or B USPSTF screening guidelines are covered without out-of-pocket cost to the patient.  In that case, we should be able to order these now without much pushback from the insurers.

Here are a few related stories:

What do you think?  Is the mortality reduction worth the huge number of false positives? Will you start ordering low dose CTs on your smoking patients? Would love to hear your thoughts in the comments.


To screen or not to screen

I read a blog post yesterday about pros/cons of CTs for lung cancer screening.  It’s here– and has good info on the risk benefit calculations to consider for that test.

BUT- the 4 points brought up are useful to consider for any screening test, so I thought I’d review them here as well.

1- Harm from the test itself.  In the case of CT scans, mammograms and other radiological tests, there is a potential for malignancy developing from the test itself.  We don’t really know what the risk is from low dose CT, but it exists.  Even blood draws (for PSA or lipid panels) carry some, albeit quite small, risk.

2. False positives.  We talk about this often with screening tests- they are set up to have a high sensitivity, often at the expense of specificity.  It is important to tell your patients (and remember yourself) that a positive test does not necessarily = bad diagnosis.  The next step to evaluate a positive test may be quite invasive- not sure about you, but I wouldn’t sign up for a bronch or VATS just for funsies. 

3. Incidentalomas.  Slightly different from #2, you may find something that you weren’t looking for, yet have to evaluate further.  This was 1 out of 13 patients in the CT for lung cancer screening study.  That’s a lot of further testing.  

4. Overdiagnosis.  This is the hardest to explain, but may be more important than we realize.  Most folks, if there is a cancer, want it out- want a cure.  But many cancers may be slow growing and never cause a problem. We are more comfortable with this concept in prostate cancer, but it exists in breast cancer, and likely lung cancer as well.  The treatments for these disease are painful, exhausting, and maybe even life threatening in and of themselves.  First, do no harm.  

So, we like screening in general medicine, but more and more, we are learning that it’s not all it’s cracked up to be.