Prognostic significance of post-bronchoscopy sputum cytology in lung cancer diagnosed by bronchoscopy: a retrospective cohort study of 625 patients.

Background: Post-bronchoscopy sputum cytology (PBS) is traditionally considered a supplementary diagnostic tool for lung cancer; however, its prognostic relevance in bronchoscopically confirmed cases remains unclear. This study evaluated the clinicopathological characteristics and prognostic value of PBS positivity in patients with bronchoscopically diagnosed lung cancer. Methods: This single-center retrospective cohort study included 625 patients with newly diagnosed, bronchoscopically confirmed lung cancer, who underwent PBS between May 2007 and December 2024. Patients were classified as PBS-positive and PBS-negative. Clinical characteristics, tumor features, and overall survival (OS) were compared. Factors associated with PBS positivity were evaluated using multivariate logistic regression. Prognostic factors for OS were assessed using univariate and multivariate Cox proportional hazards models. Survival was estimated using the Kaplan-Meier method. Results: Among the 625 patients, 82 (13.1%) were PBS-positive. PBS-positive patients were significantly younger and more likely to have advanced T-factor tumors, larger primary tumors, and proximal airway involvement. Younger age and advanced T-factor were independently associated with PBS positivity. Median OS was significantly shorter in the PBS-positive group than in the PBS-negative group (median 14.3 Conclusions: PBS positivity was associated with aggressive tumor characteristics and independently predicted poor OS in bronchoscopically confirmed lung cancer. Although its diagnostic value may be limited, PBS positivity represents a simple, noninvasive prognostic marker that may support risk stratification and clinical decision-making.