CANCER
December 16, 2010

Lung Cancer Screening, A Closer Look

CT scans can detect lung cancer early and save lives, but there are risks and costs to be weighed.

A massive new study that’s caught the eye of the scientific community and the media alike reports that CT scans significantly cut the risk for lung cancer deaths over x-rays in very heavy smokers. For a disease that kills 85% of its victims within five years, and 60% within one year, the results may sound like a godsend. And there’s no doubt about it: the study illustrates beautifully the increasing power of medical technology to catch diseases early.

But this finding also comes at a time when there are heated debates about screening recommendations for the public. For instance, two major U.S. organizations are at odds about their recommendations for the appropriate age a woman should begin mammogram screening. And CT scans are being scrutinized for their safety after some patients were recently determined to have received radiation overdoses from the scans.

After the five years of follow-up, people in the CT scan group had a 20% lower mortality rate than people who received x-rays.

The new National Lung Screening Trial (NLST), the largest of its kind, also raises some important questions about how and when tests should be offered to the public, and how we as a nation decide when and if the benefits of a medical test outweigh the risks — and the costs — of screening.

What the Study Found

In the current study, over 53,000 current and former heavy smokers between the ages of 55 and 74 were randomly assigned to receive either CT scans or x-rays. To be considered heavy smokers, participants had to have racked up 30 pack-years, meaning that they smoked one pack per day for 30 years or two packs per day for 15 years, and so on. Participants were screened with CT or x-ray, depending on which treatment group they were in, once a year for three years. After this, they were followed for five years, with lung cancer frequency and mortality being the key variables that the researchers were interested in tracking.

After the five years of follow-up, people in the CT scan group had a 20% lower mortality rate than people who received x-rays (354 people in the CT group died of lung cancer, vs. 442 in the x-ray group). They also had a 7% lower mortality rate from any cause, but the reason for this finding is still unclear. Since the data for the study still haven’t been released, speculating about the reasons behind all of the findings is somewhat difficult at this time.

Raising Even More Questions Than It Answers

Should all smokers run out and demand helical CT scans from their doctors? The answer is likely "no." For one thing, we still don’t know whether the results of the current study apply to other groups of smokers, including moderate and light smokers and younger smokers. Additionally, there is a fairly high "false-positive" rate with helical CT scans: in the current study, the false-positive rate was 25%, meaning that doctors saw masses (or "nodules") that required further investigation but turned out to be benign, which may have led to unnecessary testing and additional expense.

As you may have noticed by now, the study raises almost as many questions as it answers. For example, how do we determine whether the benefits of a particular screening procedure outweigh its risks? As mentioned earlier, CT scans may expose patients to unsafe levels of radiation if they are done too frequently. As a result, we need to think about where the balance point lies between the dangers of over-screening and the obvious dangers of missing the disease.

'I want to emphasize, a screening program is NOT just a radiology facility that has a system in place for taking your money and doing a scan.'

Along those lines, should the high false-positive rate found in the current study affect how often CT scans should be recommended to current or former smokers? On the other hand, should these benign nodules actually be considered false-positives, since they still masses that deserve investigation? And, of course, still up in the air is who should decide when and how often screening is recommended: Should it be up to the government or should it be the decisions of the individual doctors themselves? Finally, should the cost of the scans (which are not typically covered by insurance) be a factor in who gets one or not?

The Experts Weigh In

To help us think about some of these issues, we asked two experts for their thoughts in the matter. Frank Detterbeck, MD, FACS, FCCP, is the Chief of Thoracic Surgery and Associate Director of the Yale Cancer Center at Yale University. Dr. Claudia Henschke, MD, PhD is a clinical professor at Mount Sinai School of Medicine and researcher at the Biodesign Institute at Arizona State University. Both are prominent researchers in lung cancer diagnosis and treatment, and agreed to speak with TheDoctor about how they feel the new research impacts lung cancer medicine, and medicine in general.

TheDoctor: In the new study, why was lung cancer mortality lower for the CT group — is it simply because the tumors were being discovered earlier?

Frank Detterbeck: Very hard to say because we haven’t really seen the data yet. Presumably, it is because lung cancers are being discovered in a stage when the treatments we have are more effective, which is similar to your statement that we are discovering them earlier.

What's special about this study, and what are its limitations? Are there any concerns or problems with the study?

FD: The study indicates that CT scans in the context of an organized program and system are useful (again, we don’t have the details), not that having a CT scan alone is useful. To make an analogy, it is not a good idea to have your neighbor take out your appendix in his garage just because you have heard there is good data that having an appendectomy in a hospital is useful if you have appendicitis. The majority of institutions do not have a system in place, and will need to develop this. A system includes not just the scan and a radiologist, but a clinician (pulmonologist or surgeon) who is part of the team. There should be a defined process for how findings are dealt with, not a matter of making it up as you go, one patient at a time. And I want to emphasize, a screening program is NOT just a radiology facility that has a system in place for taking your money and doing a scan.

Claudia Henschke: [T]he NLST is an important study as it provides the standard methodology to the question of lung cancer screening. It [shows] that CT screening when done for 3 years reduces deaths from lung cancer when compared to chest x-ray by 20%. We are thrilled about these results as they are consistent with our reported results.

More information will follow when the NLST paper is published. For example, we were told at the RSNA [the Radiological Society of North America] by the NLST investigators that the 5-year survival rates for CT were 58% and for chest x-ray 33%. In the absence of screening (usual care), the 5-year survival rate is around 10%. So chest x-ray is better than usual care and CT is better than chest x-ray. The latter has been well known from our study and those in Japan.

Does the number of "false-positives" (or nodules) detected with CT affect how often it should be recommended?

FD: In a strict sense, no. if CT screening lowers mortality then we should use it, we just have to deal with the false positives. On the other hand, in general, dealing with the false positives is an issue. Well designed screening programs have systems in place to sort through this. The public needs to understand though, that about 50% of people undergoing CT will have a little speck detected, and the vast majority of these are nothing. Managing the potential anxiety due to false positives is an issue if there is poor understanding of the fact that it is not just a CT and seeing something or not, it is a whole system of CT, interpretation, sorting through potential issues that is useful.

CH: [T]his can be defined in so many ways, and is usually not well understood. Nodules are not "false positives" as they are real nodules that are seen in CT scans and if biopsied or taken out, the nodule could be identified in the lung tissue - thus nodules are real. They would only be false positives if they do not exist in the lung tissue and no one "almost no one" would say that.

'First of all, we need to make rational decisions and not emotional ones. Unfortunately cancer raises such emotions that people stop thinking at all. They should remember that unnecessary interventions or harm that could have been prevented also raises emotions — people just don’t get that far in their thinking.'

The real question is how should these nodules be worked up. To that end, each screening study defines those nodules which require further workup. Currently, stating it simply, we suggest nodules of a certain size be worked up…. In the NLST, they defined any nodule(s) 4 mm or larger as a positive result in the first year. When they see the same nodule(s) the next year, they count it again. That is why the percentage remained around 24% each year. But most of these are nodules the person has had for many years and they do not change. We focus on the nodules that are new in each year of screening and that is less than 6% (similar to mammography). To have an optimal CT screening program, it is critical to have guidelines or quality assurance standards as was ultimately done for breast cancer screening.

Should cost-effectiveness be part of the discussion of when to offer screenings to the public? If so, how does one determine this (and who should determine it)?

FD: I think cost-effectiveness has to be part of the discussion. To put it into a light that is perhaps more easily appreciated and often forgotten, whatever we do has to be considered in terms of the benefits and the negative impact. CT screening in some people is likely to do them more harm than good (radiation exposure, possible unnecessary interventions). Doing CT screening will result in less money to provide other services — there is no question about it — and that may well harm both the people getting scans as well as the population in general. So we have to decide to do it where it has more benefit than harm, and not when there is likely to be more harm than benefit.

CH: This depends on the definition of a positive result and workup and treatment algorithm. If it is done poorly, then it is expensive, if it is done well, it should be highly cost-effective. Currently even outside of screening, there is no real quality assurance of how incidentally found nodules on CT scans are worked up. If all would follow certain guidelines, it would be much more efficient and cost-effective.

Who should decide?

FD: That is a can of worms. I think it has to be thoughtful people who do health care policy research, and consider the data in a broad context.

Cost-benefit is a big discussion in science and medicine right now. Like this one, the mammogram debate is another that has sparked controversy (to screen or not to screen at 40), with two major U.S. organizations at odds on their recommendations. What are your thoughts on medical recommendations in general, and how — and by whom — they are decided?

FD: I think people need to remember two things. First of all, we need to make rational decisions and not emotional ones. Unfortunately cancer raises such emotions that people stop thinking at all. They should remember that unnecessary interventions or harm that could have been prevented also raises emotions — people just don’t get that far in their thinking.

Second, coming up with rational recommendations is not a matter of them versus us. Often it is interpreted as someone pursuing their own interests as opposed to your interests. Physicians are really trying to [weigh] the risks and harms for the people the recommendations are for, not trying to play off one group against another.

Third, I am all in favor of personal choice, and personal values entering into decision making, and entering into how one interprets data. But personal values does not mean you have license to only look at one side, only at the data or statements you want to, and totally ignore other facts. I think people often confuse this.

'The study does not address the large population of people who get lung cancer who never smoked, or had very minimal smoke exposure. These people account for more than many other cancers, yet they are off our radar. '

So I think that thoughtful people in the health care profession should make these decisions, taking into account the data on all sides, and different value judgments, and they should allow some flexibility where appropriate for different values. But it should not be made by people with a vested interest (often the "patient representatives" have a very biased viewpoint that is not balanced by anyone else). I don’t think the public, the legislature, special interest groups should be making the final recommendations.

How can the public stay well-informed and knowledgeable about scientific study, without being caught up in the media frenzy that sometimes comes along after an important one?

FD: I don’t have an answer, because that means fixing what is wrong with the media and our culture. It is much more about sensationalism, appealing to emotions, and personal gain for the individual and media company. Actual data, balanced views, facts, critical thinking etc have disappeared from the media to the point that most people don’t even recognize it anymore. The opinion of a (not-so random) individual who commented to a reporter is taken by the public as evidence, rather than as an isolated statement of an opinion. You’re going to have to fix this one.

What is important for the public to take home from this?

FD: It’s great news, we have to evaluate it carefully and use it appropriately or we can also do harm, and that we have a lot more work to do. For example, the study does not address the large population of people who get lung cancer who never smoked, or had very minimal smoke exposure. These people account for more than many other cancers, yet they are off our radar. We need to keep investigating all the risk factors (not just one), and keep looking for better ways to assess risk so we can rationally implement studies like this where they are going to have a positive impact.

CH: For people who consider themselves to be at risk of lung cancer, they should contact their physician or a physician involved in a screening program that has existed for some time and ask about their program. What CT scanners? [W]hat radiation dose? [W]hat is their definition of a positive result? [D]oes the center follow-up all the people they screen? In other words, what is the quality assurance of any program. It has been shown to be very important for breast cancer screening and in fact for any screening program.

Where Does This Leave Us?

Without a doubt, the new study offers a lot of hope for a disease that has, historically, been very difficult to diagnose and treat — or more specifically, it has been difficult to diagnose it early enough to treat effectively. Dr. Henschke’s earlier groundbreaking research proposed that upwards of 80% of lung cancer deaths could be prevented with standardized use of CT scans. Now, the new study now finds that CT scans offer significant benefit over conventional x-rays in detecting lung cancer. Though the study answers a lot of questions, it still leaves us with some difficult issues to grapple with. As medical technologies become more complex and medical tests more capable, heated debates about their appropriate use and distribution seem to be an inevitable result. Hopefully, as we become more informed about how these tests function, as well as their potential drawbacks, we will be able to make better decisions and recommendations about how they are used to benefit the greatest number of people at the least amount of financial and emotional cost.

If you are interested in learning more about the NLST, please see the National Cancer Institute’s Questions and Answers page: http://www.cancer.gov/newscenter/qa/2002/nlstqaQA. If you believe you are at risk for lung cancer or have any other health concerns, as always, please contact your health care provider.

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