Extended treatment duration and recurrence in successfully treated drug-susceptible pulmonary tuberculosis with cavity on chest radiograph

Background Cavity on chest radiograph is recognized as an independent risk factor for recurrence in pulmonary tuberculosis (TB), but evidence supporting extended treatment in these patients remains limited, particularly in real-world data from Korea. Methods We performed a retrospective analysis using data from a multicenter prospective cohort of patients with pulmonary tuberculosis enrolled at 18 Korean institutions, comparing recurrence rates between standard treatment (≤200 days) and extended treatment (>200 days) among drug-susceptible pulmonary TB patients with cavity on chest radiograph. Results Among 159 patients, 58 (36.5%) received standard treatment and 101 (63.5%) received extended treatment. Baseline sputum smear positivity was higher in the extended group (29.3% vs. 56.4%, p = 0.002), but 2-month culture positivity (6.3% vs. 4.4%, p > 0.999) and time to culture conversion (8.00 ± 3.91 vs. 7.45 ± 3.73 weeks, p = 0.454) were similar. Recurrence during post-treatment follow-up occurred in 4 patients (2.5%) and did not differ between groups (3.4% vs. 2.0%, p = 0.966). Treatment interruption due to adverse drug reactions was more frequent with extended treatment (1.7% vs. 7.9%, p = 0.204), while overall adverse event rates were comparable. In a fixed-time analysis using Firth’s penalized logistic regression, extended treatment showed a numerically lower risk of recurrence, although statistical significance was not reached (adjusted odds ratio [aOR], 0.07; 95% confidence interval [CI], 0.01–1.06; p = 0.056). Among covariates, low body mass index was associated with recurrence, but this estimate was very imprecise and should be interpreted with caution. Conclusion Cavity on chest radiograph alone may not be sufficient to justify routine extension of treatment beyond 200 days. Because only four recurrence events were observed, the adjusted association favoring extended treatment was imprecise and should be interpreted as exploratory rather than definitive. Larger prospective studies that systematically capture microbiologic response and detailed radiologic disease burden are needed to identify which patients with cavitary disease may benefit from individualized treatment extension.