2/19/16: LUNG CANCER: Annual CT Screening Should Be Considered for Former Heavy Smokers Up to 30 Years After They Quit the Habit

 

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Two-thirds of the patients newly diagnosed in the United States with lung cancer would not meet the U.S. Preventive Services Task Force’s (USPSTF) current criteria for screening for the disease, according to an epidemiological study by the Mayo Clinic recently published in the Journal of Thoracic Oncology.

Lead author Ping Yang, M.D., Ph.D., and her Mayo colleagues conclude that the USPSTF’s definition of “high risk” for developing lung cancer should be expanded. (See Yang et al, “Trends in Subpopulations at High Risk for Lung Cancer,” JTO 11: 194-202; http://www.jto.org/article/S1556-0864(15)00038-6/fulltext.)

Based on my own personal experience and research, I agree.

The USPSTF is an independent, nongovernmental group of national experts in prevention and evidence-based medicine. It recommends annual screening for lung cancer with low-dose computed tomography (“helical” CT scans) in adults ages 55 to 80 who have a 30 or more “pack-year” smoking history and currently smoke or have quit smoking within the past 15 years. A pack-year is the number of cigarette packs a person smoked per year multiplied by the number of years he/she has smoked or smoked.

Low-dose computed tomography uses lower amounts of radiation than a standard chest CT scan and does not require intravenous contrast dye. Computers create CT scans by processing multiple X-ray images of a target area from different angles.

The Mayo researchers recommend CT screening in former smokers ages 55 to 81 who have a 30-plus pack-year smoking history and quit smoking within the past 30 years. This extension of time, they say, would save “more lives with an acceptable amount of elevated exposure to radiation and cost.” The scientists calculate that the extension would result in 16 percent more cases being detected earlier, with only “minimal increases” in false-positive results (0.6 percent), over-diagnosis (0.1 percent), and radiation-related lung cancer deaths (4 percent).

If my 79-year-old uncle, who smoked two packs a day for more than 30 years before he quit at age 49, had been annually screened in the past 15 years, he may not have been diagnosed with Stage IV small-cell carcinoma last July. His aggressive lung cancer might have been detected before it had metastasized to his liver. I say “might” because small-cell lung cancer tends to spread very early, so most lung cancers that are found before metastasis, when they might be surgically removed, are the non-small-cell type. With screening, however, my uncle would, theoretically at least, have had a chance for curative surgery.

Lung cancer has two main types: small-cell carcinoma, also called oat-cell carcinoma, and non-small-cell carcinoma, which are microscopically distinguishable by their appearance.

The vast majority of lung-cancer cases—about 85 percent—are non-small-cell, which is abbreviated as NSCLC. Small-cell (SCLC) cases are usually, but not always, associated with smoking—on the order of 90 percent. About 85 percent of all lung cancers are caused by smoking.

Smoking is on the decline in the United States. That’s the good news. Dr. Yang and her colleagues report that the “incidence of lung cancer and mortality due to lung cancer have been decreasing among men for the past three decades and . . . recently, have begun showing a decrease among women.” Fewer than 18 percent of U.S. adults currently smoke—down from 24 percent in 1998—and more than 30 percent are former smokers, they say.

While serving as healthcare advocate for my father, I tried to discern a former smoker’s risk of developing lung cancer. I share the results of my research, some of which is detailed below, in my book, “Our Parents in Crisis: Confronting Medical Errors, Ageist Doctors, and Other Healthcare Failings.”

My father smoked on and off for about 33 years, sometimes quitting for a year at a time. He favored cigarettes, smoking about a half-pack per day, and then switched to cigars, before he finally went cold turkey in 1981 a few months before his 57th birthday.

In 2010, a routine chest X-ray revealed a single nodule on one of Dad’s lungs. Subsequent CT scans showed more nodules. After nearly 30 years of cessation, I reasoned, hadn’t he dodged the lung-cancer bullet?

My uncle thought the same thing when he was diagnosed with small-cell lung cancer in July 2015, six weeks shy of his 79th birthday, and immediately began chemotherapy. He was shocked. He figured he had beaten the odds. Sadly, not so.

Over the years, my father, a scientist-physician who came of age when “everyone smoked,” had read study reports suggesting that after 10 years of cessation, a former smoker’s risk of lung cancer declines.

In my own research, I learned that, on average, smokers lose about 10 years of life. Those who have habitually smoked cigarettes since early adulthood but stopped before age 40 can gain back these years, according to the World Health Organization’s International Agency for Research on Cancer (IARC). Regardless of when you started, however, and how many pack-years you smoked, says the IARC, if you kick the habit before age 40, you will achieve greater health benefits than if you quit at an older age. Younger lungs have a better chance of healing.

Indeed, normal aging exacts a significant toll on the respiratory system, as I discuss in my book, so, the sooner you quit, the better. According to The Merck Manual of Geriatrics, 3rd ed., the effects of normal aging on a nonsmoker’s respiration are similar to “mild emphysema.”

But even with older damaged lungs, such as my father had at age 56, studies indicate that as time after cessation increases, former smokers’ relative risk of developing lung cancer, vis-à-vis people who never smoked, decreases. Former smokers will always have “excess risk,” however, because “of residual genetic damage that persists despite cessation of smoking,” according to the IARC.

In the 2007 handbook, “Reversal of Risk After Quitting Smoking,” the IARC analyzed all of the then-available data worldwide about the hazards of smoking and the benefits of stopping. Its bottom line: “There is persistent increased risk of lung cancer in former smokers compared to never smokers of the same age, even after a long duration of abstinence [such as 30 years]. Stopping smoking before middle age avoids much of the lifetime risk incurred by continuing to smoke. Stopping smoking in middle or old age confers substantially lower lung cancer risk compared with continuing smokers.” (My emphasis added.)

In summary, the IARC writes: “Cigarette smoking causes relatively few deaths before 35 years of age, but it causes many deaths in middle age (here defined as 35-69 years) and at older ages. Although some of those killed by tobacco in middle age might have died soon anyway, many could have lived on for another 10, 20, 30 or more good years. Those who stop smoking in early middle age, however (before they have incurable lung cancer or some other fatal disease), avoid most of their risk of being killed by tobacco, and stopping before middle age is even more effective, gaining on average about an extra 10 years of life.”

My father, who died of heart disease at age 89, did not have lung cancer. His younger brother does.

I quantify Dad’s smoking history as about 15 pack-years and my uncle’s history as about 60 pack-years. Neither one fits within the USPSTF’s patient criteria for annual screening, but my uncle’s history should have raised a red flag with his primary-care physician. His doctor may have made a judgment call about screening, but it was not one that he made in consultation with my uncle. Still, there are no hard-and-fast rules about lung-cancer screening, just recommendations.

The USPSTF assigns grades to all of its recommendations and gives its lung-cancer screening recommendation, made in 2013, a “B” because such screening has more potential benefits than potential harms, but the harms may outweigh the benefits in an individual patient’s case. (See the USPSTF’s recommendation at http://www.uspreventiveservicestaskforce.org/Page/Document/UpdateSummaryFinal/lung-cancer-screening.)

False-positives, also called false alarms, are one such harm. Low-dose CT scans can suggest that a person has lung cancer when, in fact, he does not. False-positives can cause the patient needless anxiety and worry and lead to unnecessary tests and surgeries that pose their own risks. Further, people who have other serious illnesses or are in poor general health—my uncle has had heart disease for years—should not be screened if they are more likely to be harmed by the resulting treatment, including surgery, according to the USPSTF. The radiation from repeated low-dose scans also can cause cancer in otherwise healthy people.

The USPSTF based its recommendation largely on results from the National Lung Screening Trial (NLST), a multi-center study funded by the National Cancer Institute that enrolled more than 53,000 current or former cigarette smokers, between ages 55 and 74, who had smoked at least 30 pack-years. The former smokers had to have quit within the past 15 years, and all participants had to be free of symptoms or signs of lung cancer and be medically fit for surgery. Each was screened over three years, either by low-dose CT or by a chest X-ray. The NLST’s findings were released in 2010.

The Mayo researchers discuss shortfalls of the NLST—it didn’t go far enough—in their analysis and conclude that “the current USPSTF recommendation to stop screening after 15 years of smoking cessation is not reflective of the continued high risk, although participation of the expanded population in the screening setting needs to be further evaluated.”

Pending such evaluation, if I were a former smoker of at least 30 pack years and I had quit from 15 to 30 years ago, or even longer ago, I would be talking with my doctor about CT screening. One finding that the NLST clearly establishes is that a chest X-ray screening offers no advantage over a lack of screening in terms of mortality reduction. You might as well skip the chest X-ray. The low-dose CT scan, however—forget the “odds”—could be a lifesaver.

Ann, 2/19/16

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