Can CAT Scans Prevent Lung Cancer? Smoke and Mirrors

I still marvel at the accomplishments of CAT scans and imaging studies.  These technologies have revolutionized the medical profession.  Imagine foretelling 50 years ago that a new technology would emerge that could perform ‘exploratory surgery’ without an incision.   This prediction would be greeted with disbelief, if not scoffing.  Of course, there would be similar reactions if decades ago other technological feats, such as fax machines, personal computers, emails and internet, were predicted.

CAT scans save patients’ lives, prevent surgeries, make accurate diagnoses and refine treatment plans.  This is the good news.  However, as expressed repeatedly on this blog, there is a darker side of the story.

• Without doubt, too many CAT scans are performed.
• Accumulated medical radiation has health consequences.
• Resources expended on unnecessary CAT scans could be devoted to worthy health care endeavors
• Radiologists suffer from litigophobia and identify every tiny abnormality, which generates patient anxiety and more medical tests chasing these trivial results.   Off the record, radiologists will confide that these ‘abnormalities’ are inconsequential, but their formal dictations always suggest that these lesions may be ominous.  Their dictated recommendation?  Mores scans!
• CAT scans can provide patients with false security, which is the premise behind total body scans that are scamming the public.
• CAT scanning and other technologies have eroded physicians’ bedside physical examination skills.   Does anyone think we are as skilled using a stethoscope as our predecessors were?  Of course, one can argue that we don’t really need these antiquated skills anymore. 

Recently, the press went ga ga over a new study that concluded that screening CAT scans on cigarette smokers could save lives. They hyped headline of The New York Times was CT Scans Cut Lung Cancer Deaths.   The study concluded that annual chest CAT scans on smokers could reduce the risk of death by lung cancer by 20%.   Why is my reaction so cynical to what was heralded a groundbreaking development in oncology? 

First, I am always wary when study results are presented in relative terms, such as a 20% decrease in the number of deaths.  Relative percentage terms always exaggerate the clinical benefits and are misunderstood by the public, as well as the press.  For example, assume that a new cholesterol-lowering medication is prescribed to 500 people who are compared with a control group of untreated individuals to determine if the drug can prevent heart attacks.    If 4 folks in the medication group develop a heart attack, and 5 control patients do also, then the drug company can correctly claim it lowers heart attack rates by 20%.  This sounds impressive, although the true benefit that an individual realizes is trivial, since 99% of all patients suffered no cardiac event.   Can’t you just see the headline Drug Cuts Heart Attack Rate by 20%?

In the chest CAT scan study, 300 people must be screened to save one life.  Is this worth it?  Of course, if the lucky individual is in your family or mine, then any cost would justify the outcome.  However, we cannot make public policy based on anecdotes or rare favorable outcomes.   For those who argue that saving lives is worth enormous expense at the expense of others, do they also support the following positions which would save lives?

• Lowering the highway speed limit to 40 mph
• Outlawing air travel
• Prohibiting swimming
• Eliminating skiing
• Forbidding contact sports

Assuming the CAT scan study’s conclusions are correct, 299 smokers have to be screened to save a fellow inhaler.  Twenty-five percent of the scans had ‘abnormalities’ discovered that led patients into the medical labyrinth described above.  So, in the group of 300, 1 life was saved and 75 were targeted for subsequent medical assault.  When you consider that there are nearly 50 million smokers in America, imagine the billions of dollars that will be spent and the hundreds of thousands of patients who will be subjected to medical care evaluating harmless lesions.   

In addition, as doctors who have been around a while know, one study shouldn’t change the course of medical practice.  Over the past decade or two, many other groundbreaking studies were subsequently refuted.   I’m sure that physician readers can cite many examples of these medical retreats.  In six months’ time, we could learn of new study that concludes that smokers who are screened with CAT scans have a higher death rate.

A better strategy that is considerably cheaper and more effective is to try to reduce the number of cigarette smokers.  The CAT screening study cost $250 million.  What if those funds were used instead to treat nicotine addiction?  Would this have saved more lives than annual CAT scan screening?  The low tech approach, at least, is more focused on low hanging fruit, rather than aiming buckshot style at every smoker.  Moreover, I would imagine that if a smoker is told that his annual CAT scan is negative, that he will have less incentive to consider quitting.  For him, a negative scan may reinforce his belief that he will avoid a malignant fate.

Other bloggers, including KevinMD and Gary Schwitzer didn’t drink the CAT scan Kool Aide.  My advice?  When the press is serving up Kool Aide, hire a food taster.

Do I think there may a reasonable role for CAT scans in smokers?  I’m not holding my breath on this one.