CT Scans for Older Smokers Should Lead to Earlier Lung Cancer Diagnoses
May 29, 2012
A new lung cancer screening study in the Journal of the American Medical Association is touting the benefits of annual low dose CT scans for heavy smokers and former smokers who are 55 to 74 years old.
The goal of the CT scans is to detect lung cancer early enough so that treatments can change significantly the course of the disease.
A benefit-risk analysis was based on evidence review that included 53,454 participants in three difference trials. It was sponsored jointly by the American Cancer Society, the American College of Chest Physicians, the American Society of Clinical Oncology and the NationalComprehensive Cancer Network.
An estimated 226,000 Americans will be diagnosed with lung cancer in 2012, and the disease is expected to claim 160,000 lives.
Lung cancer is the leading cause of cancer death in the world and in the United States. The current five-year survival rate upon diagnosis is 16 percent.
The biggest reason for the low survival rate is late-stage detection. About 70 percent of cases diagnosed already are in stage III or stage IV, at which most treatments have proved ineffective.
CT scans could lead to earlier diagnoses and more effective treatment.
Although the latest recommendation of scans is the strongest ever, it also remains limited in scope. The review followed only people who smoked at least one pack of cigarettes daily for 30 years or two packs daily for 15 years.
And the recommendation is only for those in the specific age range (55 to 74).
The panel did not recommend screening for anyone younger or older because the risks outweighed the benefits, according to Peter Bach, M.D., of Memorial Sloan Kettering Cancer Center who was chairman of the panel that conducted the study.
One of the risks is the 20-percent chance of a false positive test, which often leads to more testing, biopsies and other invasive procedures and potential complications.
In the past, chest X-rays and lung sputum cytological exams were used to help diagnose lung cancer, but they provided a less-detailed image than a CT scan, and they also produced a high rate of false positive results.
The new study examined the risk of overdiagnosis of cancers, which has the potential to increase with more CT scans. Some cancers are discovered that have no important effect on a patient, or ones that never grow big enough to cause a problem, according to Dr. Harold Sox, professor of medicine at Dartmouth Institute who was part of the study.
“Several trials have shown the overdiagnosis of lung cancer,” said Sox in an follow-up interview with Cancernetwork.com. “The patients whose cancers were not going to cause any harm get treated often with surgery that they really wouldn’t need, if we had a way of knowing what the future of that cancer was. So these patients end up suffering the same harms from treatment and incurring the same costs of treatment, but they don’t get any benefit.”
Smoking is the primary cause of lung cancer, although it also can be caused by an exposure to asbestos. A combination of the two leads to a higher-than-normal risk of developing lung cancer. The recent study did not specifically address CT scans for those with high asbestos exposure.
The recommendation also comes with a warning that the CT scans should be done only in a multidisciplinary medical center, where there are both specialized radiologists and surgeons on staff.
Bach warned that even the most thorough annual screenings reviewed produced only a one-in-five reduction in lung-cancer deaths.
“The simple notion that screening intercepts cancers before they become advanced may be correct, but the extent to which you can do it is really quite limited, at least as this study suggests,” Bach said.