FRONTLINE CANCER: Lung cancer screening guidelines can save lives
By Scott M. Lippman
Lung cancer is the deadliest of all cancers, killing more people than all other cancers combined. Several factors make it so lethal. For one thing, lung cancer is the second most common cancer in both women (after breast) and men (after prostate). And, unfortunately, most cases aren’t discovered until the disease has advanced to a late stage.
The leading cause of lung cancer is smoking and the easiest way to lower one’s risk of lung cancer is to simply not smoke – or to quit. Now there may be an approach to earlier, effective detection in people at high risk for lung cancer: Low-dose computed tomography (CT) screenings of the lungs.
Recently, the U.S. Preventive Services Task Force issued draft recommendations urging annual low-dose CT lung scans for smokers. It’s a significant step.
The recommendation is based, in part, on research performed at UC San Diego Moores Cancer Center by Eric Goodman, M.D, and colleagues, who were part of a multi-center clinical trial funded by the National Cancer Institute.
The purpose of the National Lung Screening Trial was to compare lung cancer death rates in participants receiving low-dose CT lung scans versus traditional chest X-rays. Trial participants were all current or former smokers between the ages of 55 and 74, with at least a 30 “pack-year” history.
(A pack-year is the number of cigarette packs [20 cigarettes] smoked daily times the number of years. A patient who smoked a pack a day for 30 years would have a 30 pack-year history. Someone who smoked three packs a day for 10 years also has a 30 pack-year history.)
Trial findings reported a 20 percent lower death rate from lung cancer among participants who received low-dose CT scans, largely because they received earlier diagnoses of tumors at more treatable stages.
That’s important to note. Virtually all recent advances in lung cancer treatment have been in non-smoking-related lung cancer. Smoking-related lung cancer remains a major clinical challenge, which makes the need for effective early detection even more urgent.
CT scans have been used in clinical practice since the early 1980s, with steady improvement of the technology and image resolution over the years. The latest generation of CT scans can see lung abnormalities as small as two millimeters – the thickness of a nickel.
Still, actually detecting evidence of lung cancer remains a daunting task for radiologists. The vast majority of tiny “spots” seen on lungs are not cancer. Far more often they’re things like scarring related to an old case of pneumonia you may not remember. To rule out cancer, follow-up CT scans are ordered to look for subsequent growth. If a spot gets bigger, a biopsy may be needed to confirm diagnosis.
There is, of course, concern about radiation exposure. As their name suggests, low-dose CT scans use the minimum radiation levels necessary to produce a viable, informative image. A typical screening is the equivalent of six months of exposure to naturally occurring background radiation. And radiation risk markedly declines after age 50 – when these scans are most likely to occur.
The question patients and their doctors must ask is obvious: Does the benefit outweigh the risk? For smokers, the answer would seem to be an unambiguous yes.
The task force recommends an annual low-dose lung screening test for people who have a 30 pack-year history of smoking or who have quit within the past 15 years. It’s currently recommended only for this group of people to minimize the limitations of false positive exams and radiation exposure. There are, of course, other risk factors that a diagnostic clinician should take into account as well, such as exposure to asbestos or radon, prior history of radiation and conditions like chronic obstructive pulmonary disease. And, of course, the screening should be conducted at a center with high expertise in CT scans.
One of the biggest benefits of lung cancer screenings is the venue and moment. It’s an opportunity for the screening team to talk with a patient about smoking cessation. This is not a trivial point. Even with a 30 pack-year history, it is never too late to quit. A smoker who quits by age 50 can escape up to half of the health consequences of smoking. Quitting by 65 years can still avoid over 20 percent of the health consequences of the person who continues to smoke.
We know that quitting is hard but the long-term payoff is indisputable. At a minimum, all smokers getting a low-dose CT scan should also call the California Smokers Helpline (1-800-NO-BUTTS). The original work showing the effectiveness of the Smokers Helpline came from research at our own cancer center. It is never too late to quit the habit and reduce your chance of getting lung cancer.
—Scott M. Lippman, M.D., is Director of UC San Diego Moores Cancer Center. His column on medical advances from the front lines of cancer research and care appears in the La Jolla Light the fourth Thursday of each month. You can reach Dr. Lippman at email@example.com.
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