ESTES PARK, COLO. – Look in the near future for widespread adoption of a more selective approach to getting chest radiographs after pneumonia.
Since 2000, the American Thoracic Society, the British Thoracic Society, and the Canadian Infectious Diseases Society along with the Canadian Thoracic Society have published guidelines for management of community-acquired pneumonia. The guidelines recommend a routine follow-up chest x-ray within a couple of months after the treatment of pneumonia. The main purpose, other than in the minority of patients with ongoing pneumonia-related symptoms, is to exclude an underlying lung cancer that may have predisposed to the pneumonia.
However, recent studies suggest that the diagnostic yield of these follow-up radiographs is too low to justify a recommendation for routine imaging. The contention is that only the subset of pneumonia patients who are at increased risk for lung cancer should be targeted for a follow-up chest x-ray. A more selective approach will save substantial health care dollars and reduce radiation exposure, according to Dr. Robert L. Keith, professor of medicine and a pulmonologist at the University of Colorado at Denver, Aurora, which sponsored this update in internal medicine.
He cited what he considers "a great study" by Canadian investigators who conducted a population-based study of 3,398 Edmonton patients who had been followed for 5 years after treatment of pneumonia. The incidence of diagnosis of new lung cancer was 1.1% at 90 days, 1.7% at 1 year, and 2.3% at 5 years, which the investigators deemed too low to provide a strong rationale for routine follow-up chest x-rays (Arch. Intern. Med. 2011;171:1193-8).
Only 40% of the patients had had a follow-up chest x-ray within 90 days, suggesting that the majority of Edmonton-area physicians were already skeptical about guideline-recommended routine postpneumonia radiography. The diagnostic yield of lung cancer achieved via the imaging studies was 2.5%.
A key study finding was that none of the 79 lung cancers that were diagnosed within 5 years following pneumonia occurred in patients younger than age 40 years at the time of their lung infection, and only five cases occurred in 40- to 49-year-olds. The investigators identified three independent risk factors associated with lung cancer within 5 years after an episode of pneumonia: age 50 years or more, with a relative risk of 19; male sex, with a 1.8-fold increased risk; and current smoking, with a relative risk of 1.7.
Dr. Keith predicted that most health care systems are going to endorse the lung cancer screening strategy that proved so successful in the landmark National Lung Screening Trial (N. Engl. J. Med. 2011;365:395-409). That study in more than 50,000 subjects showed that screening via low-dose helical chest CT reduced lung cancer mortality by 20%, compared with screening by chest x-ray in high-risk patients as defined mainly by their age and smoking history.
Based upon the results of this National Cancer Institute–sponsored study and other recent lung cancer screening studies, the National Comprehensive Cancer Network has recommended routine screening using low-dose helical CT for two high-risk groups: individuals aged 55-74 years with at least 30 pack-years of smoking who either are current smokers or who quit fewer than 15 years ago, and patients aged 50 or older with at least 20 pack-years of smoking and one additional risk factor. The additional risk factors are contact with radon, occupational exposure to asbestos or other carcinogens, a history of lung cancer in a first-degree relative, a personal history of any tobacco-related aerodigestive cancer, or chronic obstructive pulmonary disease.
Dr. Keith reported that he serves on the speakers bureaus for Boehringer Ingelheim and Pfizer.