CHICAGO — Physicians can now use data to help them personalize a smoker's risk of developing lung cancer, and advise smokers about whether to undergo annual low-dose CT screening for the disease.
The International Early Lung Cancer Action Program (I-ELCAP) collected the diagnostic and prognostic data from the baseline CT screening and follow-up of almost 28,000 smokers, lead investigator Claudia I. Henschke, M.D., reported at the annual meeting of the Radiological Society of North America.
“Based on our data, we can now predict—by age, and by how much has been smoked or when a smoker has quit—what is the likelihood of [their] developing lung cancer,” she said at a press briefing.
Whether to undertake the expense of lung CT screening (around $300) is a patient's personal decision, one that should be reconsidered each year, based on the previous year's results, she said. There are now enough data to guide physicians on whether to recommend annual screening for an individual patient, she added.
The study findings suggest that the probability of an early lung cancer being detected with annual CT screening is about 80%—and with early diagnosis of early disease there is a 95% probability of a cure.
“Annual CT screening identifies a high percentage of stage I diagnoses of lung cancer, the most curable form of lung cancer,” said Dr. Henschke, professor of radiology and division chief of chest imaging at New York Hospital-Cornell Medical Center in New York. “Our study found that deaths from stage I lung cancer were surprisingly low … if treatment was pursued.”
Without screening, there is a 5-10% chance of a cancer being cured (because it would usually be discovered at a late stage) compared to a 76-78% chance of a cure with screening and early treatment, she said.
The study found that a delay in treatment of more than 6 months resulted in increased tumor size and often a higher stage of disease. And if a cancer was detected after a 2-year gap in screening, it tended to be eight times larger than a cancer detected on annual screening, with more chance of lymph node metastasis, she said.
The I-ELCAP data will soon be widely available to help physicians personalize lung cancer risk and screening issues for a wide range of patient ages and smoking histories, Dr. Henschke said.
She gave the example of a 45-year-old with a smoking history of less than 30 pack-years. The data show that this smoker's risk of developing lung cancer is 0.2%, that there would be an 80% likelihood that an early cancer could be detected with annual screening, and a 95% chance of a cure, she said.
The study also found that age has as much of an impact on the likelihood of former and current smokers developing cancer as does the number of cigarettes smoked. It found that lung cancer develops in twice as many smokers aged 50-74 years (15 per 1,000), compared with smokers under age 50 (6 per 1,000).
In addition, regardless of a patient's age or smoking history, cancer risk does not decline appreciably until 20 years after smoking cessation. “It starts decreasing slowly when they quit, and drops to half by 20 years,” she said.
Although the U.S. Preventive Services Task Force does not recommend annual lung cancer screening, even for smokers, it has switched from a negative to a more neutral position on the subject, Dr. Henschke said.
Still, most insurance companies do not cover lung CT when it is done for screening purposes alone.