Both colon cancer and atherosclerotic heart disease meet the criteria for disease screening (ie, a prolonged incubation period, an identifiable predisease lesion, and a positive clinical response to treatment when the lesion is detected early). The American Cancer Society (ACS) estimates that 50,000 people in the United States die each year of colon cancer—a preventable disease. Prevention consists of periodic screening for precancerous polyps with either a colonoscopy or a high-sensitivity stool-based test. However, if any of the stool assays is positive, a colonoscopy is required. A colonoscopy costs approximately $3000, involves a thorough bowel prep, requires a day lost from work, and is poorly tolerated by patients. Current 2018 guidelines issued by the ACS recommend screening for colon cancer beginning as early as 45 years of age and repeating the procedure every 5-10 years depending on the assessment of cancer risk.
1
Coronary artery heart disease is also a preventable disease and kills 600,000 people a year in the United States. Prevention depends on reducing cardiac risk factors and identifying individuals with arterial atherosclerotic plaque with a coronary artery calcium scan.
2
If the scan is positive, indicating coronary artery atherosclerotic disease, aggressive medical therapy to reduce low-density lipoprotein (LDL) cholesterol will significantly reduce the incidence of atherosclerotic cardiovascular disease.3
A coronary artery calcium scan costs $150, takes 10 minutes, and requires no preparation except to avoid caffeine on the day of the test. Except for the short duration of the test, no time is lost from work. The American Heart Association (AHA) recommends using the coronary artery calcium scan only to refine the intermediate-risk category profile and not for diagnosing pre-heart attack coronary artery atherosclerotic plaques.4
A comparison shown in Table 1 of routine preventive colonoscopy and not-yet-recommended routine preventive calcium scanning raises the question: Why is there a difference in prevention recommendations when both diseases are diagnosable and preventable? The answers are complex and often confusing.
This type of study design (a no treatment control group of individuals with a positive test) would not be ethically feasible.
Table 1Comparison of Two Different Disease Prevention Tests
| Colon Cancer | Atherosclerotic Heart Disease | ||
|---|---|---|---|
| Deaths per year | 50,000 | Deaths per year | 600,000 |
| Colonoscopy cost | ~$3000 | CAC scan | ~$150 |
| Treatment cost per colon cancer | ~$42,000 | Treatment cost per heart attack | ~$94,000 |
| Colonoscopy test preparation | Overnight bowel prep | CAC test preparation | Avoid caffeine on day of test |
| Retest schedule if negative (- no polyps) | Every 5-10 years | Retest schedule if negative-zero score | Every 5 years |
| Retest schedule if positive (+ polyps) | Every 3-5 years | Retest schedule if positive | Not required; medical Rx only |
| Prognostic value | Excellent | Prognostic value | Excellent |
| Availability | Widespread | Availability | Widespread |
| Patient acceptability | Low | Patient acceptability | High |
| Insurance coverage | High | Insurance coverage | Low |
| Physician reimbursement | High | Physician reimbursement | none |
| Physician involvement | High | Physician involvement | Low |
| Facility reimbursement | Good | Facility reimbursement | Low |
| Cost effective | Yes | Cost effective | Yes |
| RCT proven cancer prevention () | No | RCT proven CVD prevention () | No |
CAC = coronary artery calcium; CVD = cardiovascular disease; RCT = randomized controlled trial.
First, the expert panels that formulate recommendations are significantly different for colonoscopy and calcium scanning. For colonoscopy, the panel is primarily composed of gastroenterologists and cancer specialists.
1
These individuals have extensive clinical experience in treating patients with metastatic colon cancer with limited options for effective curative treatment. For them, prevention of precancerous disease is clearly the best approach for controlling the morbidity and mortality of this disease. In contrast, the expert panels for cardiovascular disease are primarily cardiologists with extensive experience in treating established cardiovascular disease.4
Once patients have survived a cardiovascular event, there are numerous treatments available, including aggressive medical therapy, placement of a coronary artery stent, and coronary artery bypass grafting. Unfortunately, prevention and identification of coronary artery plaques prior to events is readily available but not recommended by most cardiology-based expert panels.5
Second, the current system of financial reimbursement rewards treatment of atherosclerotic cardiovascular disease rather than prevention. In contrast to a colonoscopy for which there is adequate reimbursement for the gastroenterologist and facility, reimbursement for a coronary artery calcium scan does not adequately cover the cost of the professional time or facility, thus creating financial disincentives for performing the test.
Third, despite that cardiovascular disease kills more individuals than all cancers combined, the level of fear from cancer often exceeds the fear of having a heart attack.
6
This fear often motivates individuals to undergo an uncomfortable colonoscopy, whereas prevention of heart disease is usually left to recommendations for improved lifestyle, unless excessive risk is present.4
Furthermore, if the patient is determined to be at intermediate or high risk for cardiovascular disease by using an Internet risk calculator, the patient is often placed on a statin despite that he or she may have no atherosclerotic disease. This approach leads to poor patient compliance and unnecessary adverse medication effects.7
Fourth, changing physician behavior is difficult and requires extensive education. Major scientifically based advances in medicine require 17 years, on average, to be translated into improved patient care.
8
Colonoscopy with polypectomy has been traditional medicine for more than 20 years. In contrast, coronary artery calcium scanning has only recently been accepted as a test to further characterize the presence of disease in individuals determined to be at an intermediate risk by an Internet risk calculator.4
Despite several recent publications outlining the benefits of calcium scanning, most primary care physicians are not familiar with the interpretation of coronary artery calcium scores.9
Referral to a cardiologist is common practice for patients with a positive calcium scan. This occurs despite the evidence that further testing is not required unless the patient is having angina at rest.9
Additional physician training can help reduce these unnecessary referrals.In summary, prevention of cardiovascular disease identifies arterial wall lesions that can progress to arterial thrombosis, similar to identification of colonic polyps that can progress to colon cancer. Neither calcium scanning nor colonoscopy is a perfect test. Colonoscopy has been estimated to identify only 75% of small precancerous lesions.
10
Likewise, calcium scanning does not identify early noncalcified plaques that can rupture and result in arterial thrombosis. However, individuals with a zero calcium score have very few noncalcified plaques.11
One advantage that the coronary artery calcium scan has compared to colonoscopy is that a histological diagnosis is not required. When the scan is positive for calcium, atherosclerotic disease is present.Both the demonstrated pathology from colonoscopy biopsy and the demonstrated pathology from calcium scanning have a large evidence base for supporting intervention, preventing colon cancer and preventing heart attacks, respectively. In neither case is there the need or justification of a control arm because disease has been confirmed and successful prevention achieved in both cases. In the case of colonoscopy, polyps are removed, and in the case of coronary artery disease, the cholesterol is removed from the plaques, reversing the lesions.
Importantly, both tests often identify early stages of a lethal disease process. Colonoscopy with polypectomy has been shown to save many lives in otherwise healthy patients.
12
Coronary artery calcium scanning could do likewise, if routinely recommended to primary care physicians. Education of clinicians should be a high priority if cardiovascular disease is to be reduced. Technology-based learning collaboratives, such as Project ECHO, could assist with the adoption of this new best practice.13
As part of prevention of chronic disease in our aging population, there is a strong rationale for routine calcium scanning starting at the age of 45 years,14
the same age as is recommended for routine colon cancer screening.References
- Colorectal cancer screening for average-risk adults: 2018 guideline update from the American Cancer Society.CA Cancer J Clin. 2018; 68: 250-281
- Coronary artery calcium scanning: past, present, and future.JACC Cardiovasc Imaging. 2015; 8: 579-596https://doi.org/10.1016/j.jcmg.2015.02.006
- Efficacy and safety of more intensive lowering of LDLC cholesterol: a meta-analysis of data from 170,000 participants in 26 randomized trials.Lancet. 2010; 376: 1670-1681
- AHA/ACC/AACVPR/AAPA/ABC/ACPM/ ADA/AGS/APhA/ASPC/NLA/PCNA: Guideline on the management of blood cholesterol.Circulation. 2018; 139: e1082-e1143https://doi.org/10.1161/CIR.0000000000000625
- Cardiovascular risk assessment: a systematic review of guidelines.Ann Int Med. 2016; 165: 713-722https://doi.org/10.7326/M16-1110
- What do people fear about cancer? A systematic review and meta-synthesis of cancer fears in the general population.Psychooncology. 2017; 26: 1070-1079
- Long-term persistence in use of statin therapy in elderly patients.JAMA. 2002; 288: 455-461
- The answer is 17 years, what is the question: understanding time lags in translational research.J R Soc Med. 2011; 104: 510-520https://doi.org/10.1258/jrsm.2011.110180
- Abnormal coronary artery calcium scans in asymptomatic patients.Am J Med. 2017; 130: 394-397
- Colonoscopic miss rates of adenomas determined by back-to-back conoloscopies.Gastroenterology. 1997; 112: 24-28
- Presence and severity of noncalcified coronary plaque on 64-slice computed tomographic coronary angiography in patients with zero and low coronary artery calcium.Am J Cardiol. 2007; 99: 1183-1186.4
- Cancer screening in the United States, 2018: a review of current American Cancer Society guidelines and current issues in cancer screening.CA Cancer J Clin. 2018; 68: 297-316
- Academic health center management of chronic diseases through knowledge networks: Project ECHO.Acad Med. 2007; 82: 154-160https://doi.org/10.1097/ACM.0b013e31802d8f68
- A feasible, simple, cost-saving program to end cardiovascular disease in the United States [epub ahead of print].in: Am J Med. 2019
Article info
Publication history
Published online: July 10, 2019
Footnotes
Funding: None.
Conflicts of Interest: None.
Authorship: All authors had access to the data and a role in writing this manuscript.
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© 2019 Elsevier Inc. All rights reserved.
