Development of lung cancer in patients with nontuberculous mycobacterial lung disease

Background: As lung cancer development in patients with nontuberculous mycobacterial lung disease (NTM-LD) has never been reported, we investigated its incidence and clinical characteristics. Methods: Prospective observational cohort registry (from June 2012 to June 2017), and retrospective identification by the International Classification of Diseases, tenth revision (between March 2010 and March 2018), were used to identify NTM-LD patients aged ≥20 years who developed lung cancer. Results: Eight patients (two men and six women, one with smoking history), having Mycobacterium avium complex lung disease (MAC-LD) were identified. Four were identified from retrospective chart reviews and four from the prospective observational cohort registry (n = 361, 289 women; 311 never-smokers). All patients underwent chest computed tomography (CT) at least once a year. The incidence rate of lung cancer developing in NTM-LD patients was 124.6 per 100,000 patient-years, which was higher than the lung cancer rate in Japan. The mean age at diagnosis of MAC-LD and lung cancer was 63.6 and 74.4 years, respectively. The most common lung cancer types were adenocarcinoma (six patients) followed by squamous cell carcinoma (two patients). Lung cancer was diagnosed at early and advanced clinical stages in seven and one patients, respectively. Outcomes were favorable, except in two patients: one with advanced stage disease, and another with poor performance status. Conclusions: We identified the clinical characteristics of eight MAC-LD patients who developed lung cancer. NTM-LD may be a risk factor for lung cancer development. Periodic follow-up with chest CT might contribute to early diagnosis and curative therapy for lung cancer.