There are four main concerns that have been voiced about screening in general and in particular screening with low-dose CT.
- Radiation: As we have shown, our doses are so low as to be of either zero or negligible risk. The American Association of Physicists in Medicine counsels reassurance for all doses under 50mSv, while our LDCT always clocks in under 1mSv, and usually around 0.6mSv.
- Cost: It is true that there is a cost associated with lung CT screening. CT machines are expensive, as are the staff to run and maintain them, and the radiologists to govern their use and interpret their output. There is also the cost of ancillary staff to maintain the database and communicate results. There are also the downstream test and treatment costs of true and false positives. It is ultimately a societal question whether or not something is “worth it”, but lung cancer screening compares very favorably to other screening exams we already perform. PLOS 2013
- False positives: Erring on the side of caution, radiologists will recommend followup or biopsy inevitably on nodules that end up being benign. A report with a suspicious or indeterminate finding may cause anxiety in the patient, and it may lead to complications from other tests (e.g., biopsy). This is a legitimate concern, and for that reason it is important to have strict guidelines for reporting and a responsible program in place. Consider that a lot of the high false positive rates in the literature on lung screening come from a diversity of reasons–if a radiologist reports an adrenal adenoma (a benign nodule), is that a false positive when screening for lung cancer? If a radiologist recommends one additional 6 month chest CT to ensure the stability of a 7mm nodule she feels is likely benign, is that a false positive? If early trials had radiologists following up nodules more aggressively than we do today, should that be held against us? Our experience is that the false positive rate is well under 3%. We are not unduly alarming legions of patients, and we have been careful to include language to assuage the patient who receives a report recommending further investigation.
- Overdiagnosis: This is a controversial topic. Suffice to say overdiagnosis means radiologists correctly identify a lung cancer, the pathologist agrees it is a lung cancer, but it is likely that some of those patients would have eventually died from causes other than the lung cancer. That might be because the patient dies due to a faster acting cause (car crash, heart attack) or because that patient’s particular lung cancer was very slow-growing and non-deadly. Right now we simply do not know how to separate patients with deadly cancers from patients with non-lethal cancers–hopefully in the future we will have blood tests or tests we can perform on the cancerous tissue to help us separate out the less deadly cancers. But in the end, it seems unfair to judge a screening program for finding potentially non-lethal cancers, UNLESS overall mortality remains unaffected by screening. In fact, we know that lung cancer screening lowers mortality by at least 20% and is therefore a worthwhile endeavor.