Diagnostic Efficacy of Sputum Cytology versus Invasive Procedures for Lung Cancer: A Comparative Study

Objective and aim: Interventional diagnostic procedures such as bronchoscopy and transthoracic needle aspiration can lead to significant complications, especially in more vulnerable patients. In our study, we aimed to evaluate the characteristics of patients with high diagnostic rates via sputum cytology, a non-invasive technique. Methods: This retrospective, nested case-control study included patients who were diagnosed with lung cancer and who underwent sputum cytology at least once in our tertiary referral hospital between 2012 and 2022. Results: There were no significant differences between the groups in terms of age, gender, comorbidities, presence of hemoptysis at admission, smoking history/smoking duration, endobronchial localization, clinical stage, maximum standardized uptake value (SUVmax), or long tumor diameter (p > 0.05). However, patients diagnosed with sputum cytology were more likely to have adenocarcinoma (81.2% vs. 27.7%, p < 0.001) and less likely to have unclassified non-small cell lung cancer (0% vs. 22.9%, p = 0.03). The mean length of survival for patients diagnosed with sputum cytology was shorter than that for those diagnosed with invasive procedures (34 vs. 160 months, p = 0.03). Conclusion: Our findings suggest that sputum cytology may have diagnostic efficacy for the adenocarcinoma subtype. Despite the similar clinical stages between the groups, the higher mortality observed in patients diagnosed with lung cancer via sputum cytology may warrant updates in the staging system.