Emphysema is an independent risk factor for both non-pulmonary cancer and lung cancer, according to research published today (11 May) in the European Respiratory Journal.
Researchers carried out spirometry testing and CT examinations on 886 individuals aged 40–85 years with a smoking history of ⩾2.5 pack-years at baseline and no previous cancer diagnosis, of whom 422 had COPD, to determine whether amount of emphysema and airway wall thickness could independently predict the subsequent incidence of non-pulmonary cancer and lung cancer.
Emphysema, measured as a percentage of low-attenuation area (%LAA), was the main predictor of interest and was categorised into low (LAA less than 3%), medium (LAA 3–10%) and high (LAA ⩾10%) categories. The researchers also carried out multivariate analyses to adjust for sex, age, smoking status, age of onset of smoking and percentage of predicted forced expiratory volume 1 (FEV1).
Participants were followed up for 10 years to assess cancer rates amongst the group; 13% of participants were diagnosed with non-pulmonary cancer and 4% with lung cancer, while 0.9% received both diagnoses.
Significantly, just 18% of those not diagnosed with cancer had a LAA of ⩾10%, whereas 25% of those diagnosed with non-pulmonary cancer and 59% of those diagnosed with lung cancer had a LAA of ⩾10%; this data suggests that an increased amount of emphysema predicts an increased risk of developing non-pulmonary cancer and lung cancer. The study also showed that airway wall thickness at baseline was not a predictor of either lung cancer or non-pulmonary cancer.
The authors propose several mechanisms that may explain the association between emphysema and non-pulmonary cancer and lung cancer, including inflammatory mediators, common genetic and epigenetic factors, and exposure to risk factors such as smoking.