Mucus plug and lung cancer incidence in patients with COPD.

Airway mucus plugs are frequently observed on chest computed tomography (CT) scans in patients with chronic obstructive pulmonary disease (COPD). However, the association between the presence of mucus plugs and the risk of lung cancer in COPD patients has not been thoroughly investigated. This study aimed to determine whether mucus plugs are associated with an increased risk of lung cancer in COPD patients. We conducted a retrospective cohort study of COPD patients treated at a teaching hospital between 2004 and 2020. The primary outcome was the incidence of lung cancer, with secondary outcomes including lung cancer histologic subtypes. Among 616 COPD patients, 256 (41.7%) had mucus plugs, while 360 (58.4%) did not. Over a median observation period of 66 months, 56 patients developed lung cancer. Mucus plugs were significantly associated with an increased risk of lung cancer (adjusted HR = 2.281 [95% CI = 1.192-4.363], P-value = 0.013). Notably, this association was significant even in patients who did not meet conventional lung cancer screening criteria. Patients with mucus plugs also had a significantly higher incidence of squamous cell carcinoma (P-value = 0.001), but not adenocarcinoma. In COPD patients, the presence of mucus plugs is associated with a higher incidence of lung cancer, particularly squamous cell carcinoma.