Efficacy of Prolonged Treatment in Drug-susceptible Pulmonary Tuberculosis Patients With Cavities or Positive Sputum Culture at Two Months of Treatment: A Multi-center Registry Analysis From Republic of Korea

Abstract Background: The presence of a pulmonary cavity or a positive sputum culture at two months of treatment are recognized risk factors for recurrence in pulmonary tuberculosis (TB). Consequently, extended treatment has been recommended for these patients, although objective evidence to support this practice is limited. Methods: We conducted a retrospective analysis using data from a prospective cohort study (July 2019 – June 2023) involving TB patients from 18 institutions in South Korea. The study evaluated the effectiveness of extended (>6 months) treatment in drug-susceptible pulmonary TB patients with either a pulmonary cavity visible on chest radiographs/CT scans or a positive sputum culture at two months. Relapse rates between standard and extended treatment groups were compared. Results: Among 302 drug-susceptible pulmonary TB patients with either a pulmonary cavity or a positive sputum culture at two months, 107 received standard treatment, and 195 received extended treatment. The extended group had higher rates of sputum acid-fast bacilli smear positivity (60.5% vs. 35.3%, p<0.01), retreatment (23.7% vs. 14.2%, p<0.05), and cytopenia (14.9% vs. 6.5%, p=0.03), but similar recurrence rates (2.1% vs. 3.7%, p=0.38). Propensity score matching showed no significant difference in relapse rates (2.2% vs. 3.3%, p=0.65). Logistic regression analysis of all 994 patients identified significant recurrence factors: diabetes (OR 3.87, CI 1.28-11.71, p=0.02), chronic lung disease (OR 4.65, CI 1.36-15.87, p=0.01), retreatment (OR 3.74, CI 1.30-10.79, p=0.01), and drug interruption >7 days (OR 5.40, CI 1.64-17.84, p<0.01). Neither a positive culture at two months (OR 0.73, CI 0.09-5.46, p=0.73), presence of a pulmonary cavity (OR 0.87, CI 0.36-2.09, p=0.75), nor extended treatment duration (OR 1.57, CI 0.72-3.43, p=0.26) were significant predictors. Conclusion: This study found no evidence that extended treatment improves outcomes in drug-susceptible pulmonary TB patients with a pulmonary cavity or positive sputum culture at two months.