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CT scans: new screening tool or risky fad?

From the February ACP-ASIM Observer, copyright 2002 by the American College of Physicians-American Society of Internal Medicine.

By Phyllis Maguire

An evolving technology

Ask Dallas internist Neal L. Sklaver, FACP, about the value of full-body computed tomography (CT) scans, and he gives a mixed review.

On one hand, several of his patients who've had the procedure without his knowledge discovered early cancers. "Those scans may have been lifesaving," Dr. Sklaver said, "particularly for patients who had no symptoms or reason to suspect underlying neoplasms."

On the other hand, he pointed out that the proliferation of freestanding CT scanning centers has also led to unnecessary follow-up tests—and frightened patients. "It drives up the overall costs of health care, and patients become very anxious about any abnormality," he explained, "even when there is no reason to suspect underlying disease."

CT scan


In this body scan, the blue mass shows a lung and the loops of the colon.


Dr. Sklaver's mixed emotions reflect a growing divide within the medical community. Full-body scans—as well as cheaper scanning packages, like heart, lung and colon scans—are being aggressively marketed to consumers across the country. As a result, physicians are trying to decide whether the procedures are merely the latest consumer health craze or the dawn of a new age of diagnostic imaging.

Some physicians say they encourage patients to use the technology to check for coronary calcification or suspicious nodules. Others believe that because the utility of CT scans remains unproven, patients are throwing money away—and possibly exposing themselves to risky follow-up tests or unnecessary radiation. Those concerns have prompted the FDA to look critically at body scans' growing use.

To add to the controversy, the medical literature runs the gamut from supporting to dismissing the value of CT scan screening. While researchers prepare to spend big money to try to settle the debate, internists wonder whether to jump on the CT scan bandwagon, throw up the barricades or stay on the fence.

Patient boon or physician dilemma?

Like many health care trends, using CT scans as a wellness screening tool started in California and worked its way east. In the mid-1980s, CT technology improved enough to successfully image a beating heart. Freestanding heart scanning centers, as well as cardiac scan services in a handful of academic centers, soon cropped up.

When The Lancet published research in 1999 proclaiming CT scans vastly superior to chest X-rays in detecting small lung cancers in high-risk patients, CT scanning as a screening tool received a huge boost. Media reports led thousands of smokers to flood academic and freestanding centers with calls asking for lung scans. Entrepreneurs—including business-minded radiologists—began opening new centers with scanning services, including lung scans, "virtual colonoscopies" and full-body scans. (Body scans—which typically scan the chest, abdomen and pelvis—include heart and lung scans, but not colonography.)

In affluent areas where the centers have sprung up, consumers are embracing scanning as a sexy, new screening tool. Experts estimate that there are now 50 freestanding CT scanning centers nationwide, while more than a dozen academic medical centers offer some form of CT scanning as a "wellness" service.

Because almost no insurance companies cover scanning costs, patients don't need referrals. Instead, they shell out anywhere from a few hundred dollars for a heart or lung scan to $1,000 or more for colonography or a full-body scan.

While many physicians say patients ask ahead of time if they'd recommend the procedure, others say they don't know someone has been scanned until the patient shows up with a report. Although patients may receive a short consult with a radiologist or technician at the scanning center, they often need their physician to interpret their results.

Toni J. Brayer, ACP-ASIM Member, a primary care physician in San Francisco, recently spent time calming a patient whose virtual colonoscopy was termed "suboptimal" in his report. While the problem resulted from inadequate bowel preparation, the patient was sure the report meant he was dying. "Patients don't understand the nuances in medical reports," Dr. Brayer said, "so you spend lots of time explaining normal results, which can drive you crazy."

Wild goose chase?

Even more troubling, physicians say that the abnormalities that body scans discover—and there are many—must be followed up with often unnecessary and potentially risky testing.

"You set off on a wild goose chase, unleashing a chain of events that could hurt patients more than help them," said Colorado internist Kenneth R. Cohen, FACP. "You wind up doing expensive tests that may never have been indicated at all."

The discovery of pulmonary nodules may lead to invasive biopsies, while high coronary calcium scores may prompt unwarranted stress tests or catheterizations. One physician knew of a patient who had a kidney removed when noninvasive procedures couldn't determine the nature of a renal abnormality discovered through scanning. The abnormality turned out to be benign.

While insurers don't pay for scans, some cover the costs of tests to follow up abnormalities, a factor that drives up everyone's health care costs, Dr. Cohen said. For practices paid through capitation—like New West Physicians in Lakewood, Colo., where Dr. Cohen is medical director—pursuing false diagnostic leads hurts the group's bottom line.

Physicians are also concerned that patients may substitute scanning for an ongoing relationship with their physician. Brobson Lutz, FACP, a primary care physician in New Orleans, recalled one patient who had an angioplasty several years ago.

"I hadn't heard from him in three or four years," Dr. Lutz said, "but when he started having anginal chest pain, he went for a heart scan that showed calcification. Then he called me."

Dr. Lutz referred the patient to a cardiologist, but only after telling him the scan had been a waste of time. "He needed an angiogram, not a heart scan, and I could have told him that over the phone," he said. "It's like getting your medical care at The Sharper Image."

However, scanning supporters point out that many other screening and diagnostic procedures can also lead to unnecessary testing. And San Francisco's Dr. Brayer, who finds explaining the results a nuisance, noted that scans can serve as a powerful motivator for change. "A heart scan [that shows calcification] makes patients sit up and take notice," she said. "It's a visible, concrete piece of data that helps them pay attention to risk factors and get serious about their health."

But Colorado's Dr. Cohen said that in his experience, CT scans may also give patients the green light to continue disastrous behaviors. "If a smoker gets scanned and doesn't have cancer, that doesn't 'empower' him to stop smoking," he explained. "It reassures him that he hasn't harmed himself, which is a ludicrous conclusion."

Experts weigh in

As physicians debate the effectiveness of CT scans as a patient-driven screening tool, many are taking a closer look at the technology's effectiveness. How useful are CT scans in detecting early cancers and coronary disease, and can they help physicians predict disease or make treatment decisions?

Professional societies have not yet endorsed body scans, claiming the procedure needs more study and data. In a September 2000 position statement, for instance, the American College of Radiology concluded there is not yet "sufficient scientific evidence" that body scans are cost-effective or prolong life.

In January 2001, the American Cancer Society issued guidelines for the early detection of cancer, concluding that results from existing studies on CT scans as lung cancer screening tools were "encouraging." The guidelines also cited an "urgent" need for more data on the use of CT scans to detect lung cancer. (The guidelines are online at www.cancer.org/eprise/main/docroot/PUB/content/PUB_3_8X_
American_Cancer_Society_Guidelines_for_the_Early_
Detection_of_Cancer
.) Cancer experts also point out that it is unclear whether detecting early cancers reduces deaths or leads physicians to treat tumors that would not have become life-threatening.

Perhaps the greatest controversy about using scans for screening and diagnosis relates to coronary artery disease. A consensus paper issued in 2000 by the American College of Cardiology/American Heart Association (ACC/AHA), for example, claimed that "the majority" of the paper's authors would not recommend CT scanning to diagnose obstructive coronary artery disease because of the high percentage of associated false positives.

The authors pointed out, however, that positive calcium scores derived from heart scans "might be valuable" in determining whether an intermediate-risk patient is actually at high risk for coronary disease. They also noted that low calcium scores make "the presence of atherosclerotic plaque, including unstable plaque, very unlikely." (The paper is available online at www.acc.org/clinical/consensus/electron/ja070000326p.pdf.)

The paper also repeatedly called for ongoing investigation to determine what role heart scans can play in predicting heart disease. While research is ongoing, a debate is raging within the cardiology community about the value of heart scan screening.

"The premise is that this [heart scan] technology can pick up subclinical disease," said Maj. Patrick G. O'Malley, FACP, chief of the general internal medicine division at Walter Reed Army Medical Center in Washington, who is doing research on heart scans. "It is further presumed that doing so is a meaningful predictor of coronary events that would have been missed with conventional risk factors, such as hypertension or family history, or conventional risk assessment tools like Framingham scores. That's still very controversial."

Part of the controversy, experts say, stems from the fact that physicians don't know what precise role calcium plays in the development of coronary disease, nor the extent to which coronary calcification is a predictor of cardiovascular events.

"Many people—particularly older patients—have calcium, and many with calcium in their vessels aren't going to have blockages," said Robert A. O'Rourke, MACP, professor of cardiology at the University of Texas at San Antonio and chair of the committee that authored the ACC/AHA consensus paper. "At the same time, calcium is not very prevalent in ruptured plaques."

Howard N. Hodis, ACP-ASIM Member, director of the atherosclerosis research unit at the University of Southern California School of Medicine, added that there is not a direct correlation between calcium and atherosclerosis. A low calcium score does not mean that patients don't have dangerous levels of coronary plaque, he explained, saying that he is not convinced that calcium scoring helps assess an asymptomatic patient's coronary disease risk.

Because the role of calcification and the utility of calcium scoring have not been determined, Dr. Hodis said that he is disturbed that academic medical centers offer heart scan services. "Doctors out in private practice say, 'If they're doing them over at this prestigious institution, then they must be OK' and recommend them to patients," Dr. Hodis said. "We don't know yet if heart scans have value for patients or physicians, but we do know that scanning helps you find cases to move into your cardiology practice."

Yet Paolo Raggi, FACP, the director of noninvasive imaging and preventive cardiology at Tulane University School of Medicine in New Orleans, defended the practice of offering heart scans at academic health centers. (He said he prefers that heart scan patients be referred by physicians, but his center will scan patients without referrals.)

It is because "we don't understand atherosclerosis," he said, that he uses calcium scores from heart scans as another factor to help stratify cardiovascular risk. Those scores are particularly helpful for intermediate risk patients who, he said, make up 60% of the population who experience cardiac events.

For example, Dr. Raggi said that he would consider a 43-year-old patient with a family history of heart disease, a cholesterol level of 210 and a heart scan with significant calcification to be a candidate for statins; the same patient with a low calcium score would not be, at least not in the immediate future.

In response to the charge that screening with CT scans will drive up health care costs, Dr. Raggi said that he believes it would be cheaper to screen (at $400 a test) the roughly 20 million American patients at intermediate risk for heart disease to determine who really needs aggressive drug treatment. By comparison, he said, putting each of those patients on a regimen of statins could cost $1,000 a year per patient.

And he believes that the difficulties practitioners can encounter interpreting scan results and their many false positives mean that academic health centers should be involved in CT scan screening. "Some private centers are being run by very conscientious physicians," he said, "but I'm afraid there will be a proliferation of centers thrown up by businessmen who see nothing but a chance to make an easy $500."

Looking to research

Several studies are attempting to resolve some of the uncertainties about CT scans for screening. The National Heart, Lung and Blood Institute, for instance, has launched the $68 million, 10-year Multi-Ethnic Study of Atherosclerosis (MESA) to test different methods of detecting early heart disease. As part of the study, researchers will use CT scans to see if coronary calcification effectively predicts cardiovascular disease.

And the National Cancer Institute recently funded a $200 million, 20-site study involving 50,000 patients at high risk for lung cancer. The goal? To determine whether researchers can reduce lung cancer mortality by using CT scans instead of chest X-rays.

Until research provides definitive answers, some freestanding scanning centers are trying to separate themselves from the pack by advertising that board-certified radiologists are always on site to interpret results. One such company is AmeriScan, which offers full body scans and smaller scan packages at four sites in Arizona and California.

AmeriScan's medical director, Craig A. Bittner, MD, a cardiovascular interventional radiologist, left a position at Stanford University School of Medicine to start the company. He said that maintaining quality is the only way to establish the industry's credibility in the eyes of the public and the medical profession—and keep down the number of false positives associated with CT scanning.

Freestanding centers are also being scrutinized by the FDA, which is taking a dim view of body scans. Agency officials said they are concerned that using body scans for screening exposes healthy patients to unnecessary radiation (see "An evolving technology," page 14) and potentially risky follow-up. An agency spokesperson explained that the FDA approved the use of CT scans only for diagnostic purposes under the direction of a physician. As a result, the agency is exploring legal options to curtail the use of body scans as self-referred screening tools.

Dr. Bittner called the FDA's concerns "unfortunate," saying "there is no precedent for the FDA regulating the application of a technology." At the same time, Dr. Bittner said that AmeriScan plans to double the number of its sites every year, and that he is convinced neither the technology nor patient demand for it will go away.

"This is just the tip of the iceberg," Dr. Bittner said of the current scanning industry. "Diseases aren't going away, and as more baby boomers age and get educated, they're going to understand the strength of early diagnosis."

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An evolving technology

Computed tomography (CT) scanning technology, which combines X (electromagnetic) radiation with computer programs to create a readable image, was developed in the 1970s. Until the late 1980s, however, the usefulness of CT scanning was limited by its speed. After each X-ray scan—also known as a "slice"—the patient had to be moved before the next slice could be taken.

"The best scanners then could do maybe eight scans a minute because they were limited by the 'shoot-and-move' technique," said Elliot K. Fishman, MD, professor of radiology and director of diagnostic radiology and body CT at Baltimore's Johns Hopkins Hospital.

The technology was revolutionized by innovations that dramatically boosted CT scanning speeds. One innovation was the development of electron beam CT (EBCT), which uses prisms to scatter the X-ray beam and take a faster picture.

Spiral CT scans were another advance: While the patient continues to move on a conveyor table, the X-ray tube now rotates or spirals around the patient, allowing much faster scanning speeds.

"Now you could scan an entire chest with a 3-mm slice in about 25 to 30 seconds, the time it takes to hold a single breath," Dr. Fishman said. "That was a major advantage." Those improvements allowed both EBCTs and spiral CTs to image a beating heart.

In the late 1990s, a new generation of machines was developed, known as multi-detector (also multi-slice or multi-row) spiral CT scanners. Instead of taking one slice per X-ray tube rotation, four beams are shot through the patient at once, yielding four simultaneous slices with data integrated into a composite picture. (The technology continues to evolve, Dr. Fishman said: The newest machines can take eight slices per rotation, while scanners to be introduced later this year will take 16.)

There are several advantages to scanners' increasing speed. For one, patients don't have to hold their breath as long. IV contrasts (which are typically not used with CT scans as screening tools) are at "a high level for only a small period of time," so faster speed makes better use of contrast material. And image resolution at higher speeds is "substantially increased," Dr. Fishman said, making it possible for CT scans to pick up coronary calcification and small nodules.

Evolving technology has also made it possible to decrease the patients' radiation exposure when being scanned. The new generation of scan detectors, Dr. Fishman said, is more efficient than their technological antecedents and needs 30% less radiation than conventional CT scans. He also pointed out that CT scan manufacturers have developed software that tailors radiation doses to patient size, keeping doses down.

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