Seeing Is Believing: Why Coronary Calcium on Lung Cancer Screening Matters
Because every smoker is getting optimal coronary artery disease risk factor management...not.
Cigarette smoking is to atherosclerosis as gasoline is to fire: a powerful accelerant. Thus, it makes sense that smokers are at higher risk for adverse events related to coronary heart disease (CHD), such as myocardial infarction and sudden cardiac death, compared to their non-smoking peers. It also makes sense that smokers need more aggressive risk factor modification, chief among them of course smoking cessation.
In a recent JACR opinion piece, Adam Bernheim, MD, and his co-authors assert that coronary calcium scoring (CCS) on lung cancer screening (LCS) CT has "dubious value." Why? We know that CCS is most helpful in risk stratification for patients at moderate risk of downstream coronary events. For these patients, their physicians can decide how aggressive to be with respect to risk-factor-modification strategies, such as prescribing lipid-lowering medication. Those who qualify for LCS CT are, by definition, in the high risk category (except for women at the lower end of the LCS age range) for CHD events, which also qualifies them for guidelines-based statin therapy. Therefore, the authors argue, these patients are already taking statins, making CCS moot.*
I thought this caveat too big to just accept at face value, so for the most recent consecutive twenty patients who underwent LCS CT at my institution, I checked whether they were on statins. (I did not check whether they also carried a diagnosis of hyperlipidemia.) Of these twenty, thirteen were former smokers and seven were active smokers. Twelve (60 percent) were on statins and eight (40 percent) were not. So there goes the assumption that all LCS-eligible patients are on statins. Why aren't they?
Perhaps PCPs in my region are undertreating this patient population. Perhaps the patients declined statin therapy. Maybe a few individuals had a prior adverse reaction to statins. There may be a number of other potential reasons these patients aren't already on statins.
The main rationale for CCS in LCS-eligible patients not on statins is not for incremental risk stratification. Instead, the goal may be to effect patient behavioral modification and provider compliance with existing guidelines. The absence of coronary calcium is good news: even if risk-factor modification has not been optimized prior to LCS CT, starting statin therapy afterward may slow the development or progress of atherosclerosis. The presence of coronary calcium can also be good news. Visualizing coronary calcification has been demonstrated to be a powerful motivator for patients to adhere to prescribed preventive medical treatment and to adapt recommended lifestyle changes. Seeing is believing.
What about those patients already on statins? The presence of little-to-no coronary calcium may be reassuring for patients and their providers to demonstrate that by virtue of the steps they've taken, such as smoking cessation and statin therapy, they may be well on their way to lowering the patient's long-term CHD event risk. If there is a larger-than-expected amount of coronary calcium, patients and providers can have a conversation about what preventive measures they could ramp up, create a plan for how they will deal with the possibility of subclinical coronary atherosclerosis transitioning to symptomatic heart disease (such as timing of stress testing or coronary catheterization), and review signs and symptoms of heart attack with patients and their family members.
Rather than turning a blind eye to coronary calcium on LCS CT, let's offer these patients not only the possibility of finding lung cancer when it is subclinical, early stage, and potentially curable, but also the opportunity to decelerate the progress of subclinical coronary atherosclerosis and potentially prevent major cardiac events. Either way, we could save a life or two or more.
*Although the article authors also argue against CCS on LCS CT for technology-based reasons, subjective assessment of coronary calcium on non-ECG-gated LCS CT has been demonstrated to correlate with traditional ECG-gated CCS CT by researchers including the Early Lung Cancer Action Program, the NELSON trial, and the National Lung Screening Trial groups (2-5).
So this begs the question, does cac on CT screening necessitate an "S" category in lung rads scoring? We have disagreement in our group.