January 25, 2008 - The presence of emphysema seen on low-radiation-dose CT (LDCT) images appears to be an independent risk factor for lung cancer, investigators report in the December issue of Chest.
"Lung cancer screening using low-radiation-dose CT is a promising strategy currently undergoing intensive research efforts," note Javier J. Zulueta, M.D., the University of Navarra, Spain, and colleagues. "An important aspect of these strategies is the ability to identify patients at high risk for lung cancer who may benefit the most from smoking cessation treatments, early diagnosis or chemoprevention."
The researchers examined the significance of emphysema detected on LDCT of the chest using data from a prospective cohort of 1,166 former and current smokers enrolled in a lung cancer screening study. The participants underwent a baseline LDCT and spirometry followed by annual repeat LDCT studies for up to five years.
Emphysema was detected on 29 percent of the baseline LDCTs. Twenty-five percent of patients had airway obstruction on spirometry. Of the patients with emphysema on CT, 53 percent had no airway obstruction.
Overall, 23 subjects were diagnosed with lung cancer. Of these, 17 cases were detected on baseline screening, and six were detected on annual repeat screening.
Results of univariate analysis showed that the incidence of lung cancer among subjects with and without emphysema on LDCT was 25.0 per 1,000 person years and 7.5 per 1,000 person years, respectively (risk ratio, 3.33).
"In the stratified analysis, the presence of emphysema on LDCT was associated with an increased likelihood of a lung cancer diagnosis among subjects without airway obstruction (RR, 4.33)," Dr. Zulueta and colleagues report. "When the analysis was limited to participants with airway obstruction on spirometry, no relationship between emphysema on LDCT and lung cancer risk was found."
Multivariate analysis showed that the presence of emphysema on LDCT was associated with an increased risk of lung cancer after adjusting for potential confounders (RR, 2.51). Airway obstruction was not independently associated with an increased lung cancer risk.
The investigators conclude that "emphysema on LDCT is an independent risk factor for lung cancer." If the results are confirmed, "this information can be used to select candidates for lung cancer screening or chemoprevention trials."
Source: By Reuters Health, January 10, 2008
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