28 Feb, 17 | by EBM
By Dr. Geoffrey Modest
A recent real-world study reported on the results of the implementation of the low-dose CT (LDCT) lung cancer screening in smokers at 8 VA hospitals (see doi:10.1001/jamainternmed.2016.9022).
- 93,033 primary care patients assessed: 4246 met criteria for screening, 2452 [57.7%, a pretty low number…] agreed to be screened: 96% men, mean age 65,
- Of note, there was a large variation in the number of positive LDCT screens by site, varying from 31% to 85%. [This raises the issue of lack of consistency in radiologist interpretation of LDCTs, which is also found in mammography evaluation and for several other x-rays]
- 1257 (60%) had lung nodules, of whom 1184 (56%) required tracking (solid nodules <8mm without suspicious features (irregular or speculated borders) and not known to be new or growing based on prior imaging, ground glass nodules >5mm, or mixed solid and round glass nodules of any size)
- 42 (2%) required further evaluation but did not have cancer
- 31 (1.5%) had lung cancer within 330 days of follow-up
- False-positive rate of 97.5% !!!
- 857 (41%) had incidental findings (e.g. emphysema, other pulmonary abnormalities, coronary artery calcification)
- They calculated that 880,899 patients in the VA system would meet criteria for lung cancer screening
- The recommendation for LDCT screening of smokers was largely based on the National Lung Screening Trial (NLST), but
- There were significant differences in the demographics of these VA patients’ vs the NLST participants: more men, older group (53% were 65 or older), more current smokers (57% vs 48%)
- The rate of positive screens was more than twice as high in this study (60%, vs 27% in NLST)
- I have sent out many blogs on LDCT screening in the past (see below), but my concerns are several: the large number of false positives, the amount of radiation, the fact that one good trial (NLST) which lasted only 3 years generated a massive screening initiative (which can last up to 22 years, or 25 years if you go by the USPSTF guidelines!!), had very few lung cancers actually detected (despite their extrapolation which projected saving 3 deaths/1000 high-risk individuals screened), did not include some high risk patients and did include some low risk ones, and reinforced the false perception that the main problem with smoking is lung cancer.
- The editorialists wrote a very powerful response (see doi:10.1001/jamainternmed.2016.9446), noting:
- For every 1000 people screened:
- 10 would be diagnosed with early-stage lung cancer (potentially curable)
- 5 diagnosed with incurable advanced-stage lung cancer
- 20 would undergo unnecessary invasive procedures (bronchoscopy and thoracotomy) because of the screening
- 550 will have unnecessary alarm and repeated CT scanning, with its attendant radiation [which, as noted in my prior blogs, actually increases the average radiation exposure from the low-dose from the initial screen by 4-fold to that of a regular chest CT, given the follow-up requisite high-dose regular CTs, PET scans etc.]
- They also point out that many of the anticipated problems from LDCT screening were articulated by the CMS advisory body MEDCAC (Medicare Evidence Development and Coverage Advisory Committee), noting that they had “low confidence” that LDCT benefits would exceed the risks, and “high confidence” that evidence gaps remained after the initial studies (NLST did find benefit, though 3 European trials found no benefit)
- For every 1000 people screened:
So, to me, this VA study suggested several things:
- I think it reinforces that there really should be multiple studies done in different patient populations (include some “real-world” sites, where the recommendations will actually be implemented)
- That it is a bit crazy to generalize from a 3-year study to guidelines which could potentially expose millions of people to 22+ years of radiation.
- That all of this is especially true before we embark on a screening test which is so resource-intensive. Not just the cost (which is a lot, and could be used for many other social or medical issues which are underfunded), but also the intensity of resources (developing systems to track these patients, carving out time from the already time-limited primary care encounter to deal with shared decision-making, being sure that the patient qualifies for the study, doing the referral for the screenings over the years, devoting the time and resources of other office staff to dealing with all of this as well, and then doing all of the above for following up on the very common incidental findings (41% in this study), false positives (97.5%) etc….
- And, by the way, another article in the same journal (see doi:10.1001/jamainternmed.2016.9016 ) found that from 2010 to 2015 (NSLT was published in 2011), there were large % increases in LDCT done in never-smokers and low-risk smokers, such that many more of these who actually do not qualify per the guidelines are getting LDCTs than those who do qualify, suggesting that this very low-risk group is pretty undoubtedly getting risk with almost no benefit, and that there is some collateral damage to having guidelines: either confusion on the part of the clinicians, or insistence on the part of patients who do not want to be denied this (???) potentially life-saving intervention……
- And, speaking of collateral damage, one of the big concerns in primary care is that we are working in a quite litigious society, and we may be medico-legally responsible if a smoker who meets criteria for LDCT does not get one, even if logic is on our side…
Prior related blogs:
- See http://blogs.bmj.com/ebm/2015/08/26/primary-care-corner-with-geoffrey-modest-md-another-downside-of-lung-cancer-ct-screening/ which looked at a small number of VA patients, revealing their misperceptions about the screening, with some thinking that since the CT was okay, they could continue smoking (one concern is that LDCT focuses on lung cancer in smokers, but the highest mortality/morbidity is actually from smoking-related atherosclerotic disease)
- See http://blogs.bmj.com/ebm/2016/07/20/primary-care-corner-with-geoffrey-modest-md-lung-cancer-screening-for-smokers-an-individual-risk-based-approach/ which questions the criteria for LDCT screening, noting that many very high risk patients do not actually qualify and many low risk ones do
- See http://blogs.bmj.com/ebm/2014/01/02/primary-care-corner-with-dr-geoffrey-modest-time-to-screen-for-lung-cancer-with-ct-scanning/ which brings up the issues of radiation exposure, etc.