Preventing ASCVD Events: Using Coronary Artery Calcification Scores to Personalize Risk and Guide Statin Therapy

CAC Scores on Annual LDCT Scans

Because LCS requires annual LDCT scans, primary care practitioners and patients need to understand the significance of changing CAC scores over time. For individuals not on statin therapy, increasing calcification is a marker of progression of subclinical atherosclerosis. Patients undergoing LCS not on statin who have progressive increases in their CAC should consider initiating statin therapy. Individuals who opted not to initiate statin therapy who subsequently develop CAC should be re-engaged in a discussion about the significance of the finding and the clinically proven benefits of statin therapy in individuals with subclinical atherosclerosis. These considerations do not apply to individuals already on statin therapy. Statins convert lipid-rich plaques to lipid-depleted plaques, resulting in increasing calcification. As a result, CAC scores do not decrease and may increase with statin therapy.³⁹ Individuals participating in annual LCS should be informed of this possibility. Also, in these individuals, referral to specialty care as a treatment failure is not supported by the literature.

Furthermore, serial CAC scoring to titrate the intensity of statin therapy is not currently recommended. The goal with moderate-intensity statin therapy is a 30% to 49% reduction from baseline LDL-C. If this milestone is not achieved, the statin dose can be escalated. For high-intensity statin therapy, the goal is a > 50% reduction. If this milestone is not achieved, then additional lipid-lowering agents, such as ezetimibe, can be added.

Further ASCVD Testing

LCS with LDCT is associated with improved health outcomes, and LDCT is the preferred imaging modality. The ability of LDCT to detect and quantify CAC is sufficient for clinical decision making. Therefore, obtaining a traditional CAC score increases radiation exposure without additional clinical benefits.

Furthermore, although referral for additional testing in those with nonzero CAC scores is common, current evidence does not support this practice in asymptomatic individuals. Indeed, the risks of LCS include overdiagnosis, excessive testing, and overtreatment secondary to the discovery of other findings, such as benign pulmonary nodules and CAC. With respect to CAD, randomized controlled trials do not support a strategy of coronary angiography and intervention in asymptomatic individuals, even with moderate-to-severe ischemia on functional testing.⁴⁰ As a result, routine stress tests to diagnose CAD or to confirm the results of CAC scores in asymptomatic individuals are not recommended. The only potential exception would be in select cases where the CAC score is > 1000 and when calcium is predominately located in the left main coronary artery.

Conclusions

LCS provides smokers at risk for lung cancer with the best probability to survive that diagnosis, and coincidentally LCS may also provide the best opportunity to prevent ASCVD events and mortality. Before initiating LCS, clinicians should initiate a shared decision making conversation about the benefits and risks of LDCT scans. In addition to relevant education about smoking, during shared decision making, the initial ASCVD risk estimate should be done using the PCE and when appropriate the benefits of statin therapy discussed. Individuals also should be informed of the potential for identifying CAC and counseled on its significance and how it might influence the decision to recommend statin therapy.

In patients undergoing LCS with an estimated risk of ≥ 7.5% to < 20%, moderate-intensity statin therapy is indicated. In this setting, a CAC score > 0 indicates subclinical atherosclerosis and should be used to help direct patients toward initiating statin therapy. Unfortunately, in patients undergoing LCS a CAC score of 0 might not provide protection against ASCVD, and until there is more information to the contrary, these individuals should at least participate in shared decision making about the long-term benefits of statin therapy in reducing ASCVD risk. Because LDCT scanning is done annually, there are opportunities to review the importance of prevention and to adjust therapy as needed to achieve the greatest reduction in ASCVD. Reported elevated CAC scores on LDCT provide an opportunity to re-engage the patient in the discussion about the benefits of statin therapy if they are not already on a statin, or consideration for high-intensity statin if the CAC score is > 1000 or reduction in baseline LDL-C is < 30% on the current statin dose.