Blog | Tuesday, January 15, 2013

QD: News Every Day--CT scans reconsidered for screening for high-risk lung cancer

Doctors should counsel high-risk patients about lung cancer screening with low-dose computed tomography, according to guidelines issued by the American Cancer Society.

The organization's recommendations state that clinicians with access to high-volume, high-quality lung cancer screening and treatment centers should counsel healthy patients ages 55 to 74 years who have a 30-pack-year smoking history and who currently smoke or have quit within the past 15 years.

The full text of the guidelines appears free online at CA: A Cancer Journal for Clinicians, as does a two-page handout for patients.

Among the other recommendations:
--Smoking cessation is still a priority and screening is not an alternative to quitting;
--Clinicians should not discuss CT lung cancer screening with patients who do not meet the criteria, and counter requests for it by citing the uncertainty regarding the balance of benefits and harms in groups outside this recommendation; and
--Chest X-rays should not be used for cancer screening.

The guidelines are heavily based on results from the National Cancer Institute's National Lung Screening Trial (NLST). In this study, a group of adults at high risk of lung cancer were randomized to receive three annual lung cancer screening examinations with low-dose computed tomography or three annual chest X-rays. There was a statistically significant 20% reduction in lung cancer mortality (95% confidence interval [CI], 0.73 to 0.93) and a 6.7% reduction in deaths from any cause (RR, 0.93; 95% CI, 0.86 to 0.99) comparing low-dose CT tomography to annual chest X-rays.

Otis W. Brawley, MD, FACP, offers a perspective on the statistics involved in the guideline. He is a co-editor of the journal, a co-author on the paper and chief medical and scientific officer for the American Cancer Society.

Dr. Brawley wrote that NLST results showed that more than 53,000 people in good health, aged 55 and over and at high risk of lung cancer because of their smoking history were randomly assigned to either a treatment group that received low-dose spiral CT scans or a control group that received chest X-rays.

There were 356 lung cancer deaths among those who underwent a CT scan, compared to 443 who'd received X-rays. As Dr. Brawley explains, "The difference of 87 lives saved from a lung cancer death represents a statistically significant 20% decrease in risk of lung cancer death. One way of looking at this is: among about 27,000 people screened with a CT scan, 87 lung cancer deaths were prevented, but 356 lung cancer deaths still occurred."

For harms of screening, of the nearly 27,000 people who got three CT scans, 40% had an abnormal finding and needed more and sometimes invasive testing, more than 95% of which did not result in a cancer diagnosis.

Among those who underwent CT screening, 16 participants died within 60 days after an invasive diagnostic procedure, although not necessarily from the procedure itself. Six of the 16 did not have lung cancer.

"Some have interpreted the NLST as showing that for every 5 to 6 lives saved from lung cancer, 1 life was lost due to screening and the additional diagnostic procedures," Dr. Brawley wrote.

He concluded, "As technology improves, there is growing concern about the identification of some small tumors that are technically cancer but are actually of no threat. These 'overdiagnosis' tumors may lead to unnecessary treatment, unnecessary complications, and unnecessary discomfort--at times even death--for the patient. For those of us in the medical profession, it's our job to keep these as few and far between as possible."