Prior respiratory disease tied to lung cancer

Chronic bronchitis and emphysema are associated with lung cancer, according to a new study by researchers from Europe and Canada in the American Journal of Respiratory and Critical Care Medicine.

Respiratory conditions are often present with lung cancer, but few studies have looked at more than one condition at a time. The researchers examined lung cancer risk associated with chronic bronchitis, emphysema, tuberculosis, pneumonia, and asthma. They found that bronchitis and emphysema are both positively associated with lung cancer -- as is pneumonia that occurs less than two years before the diagnosis.

The researchers found that people with chronic bronchitis, emphysema, and pneumonia had an increased risk of lung cancer, compared with persons with no diagnoses of prior respiratory disease, wrote researchers from the International Agency for Research on Cancer (IARC) in Lyon, France, and colleagues at several other centers (Am J Respir Crit Care Med, July 23, 2014).

The project relied on pooled data from case-control studies to examine the association between multiple prior respiratory diseases and lung cancer, gathering data from 12,739 cases and 14,945 controls (mean age 63 years) from seven studies.

As measured by odds ratio (OR), for men the most significant relationship between lung cancer and a prior respiratory disease was seen with pneumonia diagnosed two or fewer years prior to lung cancer but not for longer periods (OR = 3.31). Next on the list was emphysema (OR = 1.50), while chronic bronchitis was the weakest of the three but also demonstrated a positive relationship (OR = 1.33).

Among the women study, two diseases -- emphysema and pneumonia -- remained positively associated with lung cancer after adjusting for confounding factors, though the relationship was not statistically significant for emphysema. More women than men had never smoked, and on average women consumed less tobacco than men. Chronic bronchitis was associated with an increased risk of lung cancer (OR = 1.25).

The relationships varied between different patterns of diagnoses for prior respiratory diseases lung cancer, with emphysema being especially important while asthma and bronchitis that co-occurred were not associated with lung cancer, the group wrote.