Background: Multiple studies have demonstrated an increased risk of lung cancer in the presence of emphysema detected visually on computed tomography (CT) independent of smoking history and airflow obstruction. The relationship between emphysema and specific histologic subtypes of lung cancer remains uncertain.

Objective: To determine the extent to which emphysema on chest CT is associated with lung cancer histology.

Methods: Cross-sectional analysis of consecutive lung cancer patients referred to the Jewish General Hospital was performed (2001-2009). All those with demographic data, smoking history (pack-years), documented histology and chest CT were included. Emphysema was graded on CT by three readers, using a standardized rubric. Odds of each lung cancer subtype were compared between patients with and without emphysema, and adjusted for age, sex, physician diagnosed COPD and smoking history by multiple logistic regression.

Results: Complete data were available for 498 lung cancer patients (mean age 68 years; 44% female; 16% never smokers; 53% without emphysema on CT). The most common histologies were adenocarcinoma (242 [49%]), squamous (71 [14%]), undifferentiated (48 [10%]) and small cell carcinoma (42 [8%]). The presence of emphysema was associated with increased odds of squamous (OR 3.1; 95% CI 1.8-5.3) and small cell (OR 2.1; 95% CI 1.1-4.1) carcinoma. After adjustment for age, sex, COPD and smoking history, emphysema was associated with squamous (adjusted OR 2.6; 95% CI 1.4-4.8) but not small cell (adjusted OR 1.5; 95% CI 0.76-3.1) carcinoma. Sensitivity analysis was performed by sequential censoring of each histologic subtype yielding similar results. Adenocarcinoma was less common in the presence of emphysema relative to squamous and small cell carcinoma (adjusted OR 0.62; 95% CI 0.41-0.92). When these latter histologies were censored, no significant association between adenocarcinoma and emphysema was observed (adjusted OR 1.0; 95% CI 0.49-2.1).

Conclusions: Relative to other histologic subtypes, the odds of squamous carcinoma were significantly increased among lung cancer patients with emphysema after adjustment for age, sex, COPD and smoking history. Other common subtypes were not independently associated with emphysema.