PURPOSE: Emphysema is associated with increased risk of lung cancer independent of smoking history and airflow obstruction. The specific lung cancer type(s) associated with emphysema remain unknown.
METHODS: Cross-sectional analysis of consecutive lung cancer cases referred to the pulmonary oncology centre of the Jewish General Hospital (Montreal) was performed (2001-2009). All lung cancer cases with age, sex, smoking history (pack-years), histology and chest CT were included. Emphysema was graded qualitatively on chest CT by two readers. The relative proportion of each lung cancer type was determined among patients with and without emphysema and adjusted for age, sex and smoking history by multiple logistic regression.
RESULTS: Age, sex, histology, smoking history and CT chest were available in 498 lung cancer patients (mean age 68yrs; 221 [44%] female). Seventy-eight were never smokers (16%) and 263 (53%) had no emphysema on chest CT. The most common histologies were adenocarcinoma (242 [49%]), squamous carcinoma (71 [14%]), undifferentiated carcinoma (48 [10%]) and small cell carcinoma (42 [8%]). Presence of emphysema was associated with increased risk of squamous (OR 3.1 95% CI 1.8-5.4) and small cell (OR 2.2 1.1 95% CI 1.1-4.1) histology. However, after adjustment for age, sex and smoking history, emphysema was significantly associated with squamous (OR 2.8 95% CI 1.5-5.0) but not small cell (OR 1.6 (0.78-3.2) histology. When these histologies were excluded from the analysis the presence of emphysema was not associated with adenocarcinoma or other histologies. A significantly greater proportion of patients with squamous carcinoma had quit smoking ≥10 years prior to diagnosis compared to small cell histology (20% vs 10%, p=0.03).
CONCLUSION: The odds of squamous (but not small cell) carcinoma was significantly increased among lung cancer patients with emphysema after adjusting for smoking history.
CLINICAL IMPLICATIONS: These findings suggest that squamous carcinoma may be related to the pathologic process of emphysema in addition to the direct carcinogenic effect of smoking. In contrast, small cell carcinoma is associated quantitatively and temporally with smoking history. Any association with emphysema likely represents confounding.
DISCLOSURE: Benjamin Smith, No Financial Disclosure Information; No Product/Research Disclosure Information