Abstract Rationale The optimal timing for initiating treatment in patients with Mycobacterium avium complex pulmonary disease (MAC-PD) remains uncertain. This study aimed to identify clinical factors associated with the decision for watchful waiting and to evaluate its impact on all-cause and respiratory infection-related mortality. Methods We retrospectively analyzed 1,205 patients with newly diagnosed MAC-PD across 18 hospitals (tertiary and secondary care) in Kyushu, Japan, between 2010 and 2017. Patients were categorized into those who initiated antimycobacterial therapy within 5 years of diagnosis and those managed with watchful waiting. Univariate and multivariate logistic regression analyses were used to identify factors associated with treatment initiation. Survival analyses were performed to compare all-cause and respiratory infection-related mortality according to the timing of therapy initiation. Results Among the 1,205 patients, 485 (40.2%) initiated treatment within 2 months of diagnosis, whereas 687 (57.0%) were initially managed with watchful waiting. During follow-up, 172 (25.0%) of the latter group subsequently started treatment, resulting in a total of 667 (55.3%) patients receiving therapy within 5 years. Independent factors associated with treatment initiation included younger age, lower body mass index, diabetes, MAC-PD related symptoms, cavitary lesions, and positive sputum smears. Among 488 patients who received antimycobacterial therapy for at least 6 months, delayed treatment initiation (≥2 months and ≥1 year after diagnosis) did not increase all-cause or respiratory infection-related mortality when analyses were anchored at treatment start. Conclusions In carefully selected patients without high-risk features, watchful waiting with delayed treatment initiation did not adversely affect all-cause or respiratory infection-related mortality. These findings support individualized management and align with current guideline recommendations for patient-specific timing of therapy, underscoring the importance of close monitoring to initiate treatment promptly upon disease progression. This abstract is funded by: Non-profit Organization Aimed to Support Community Medicine Research in Nagasaki; Research Center for GLOBAL and LOCAL Infectious Diseases, Oita University
Ide et al. (Fri,) studied this question.