TUBERCULOSIS AND LUNG CANCER

The occurrence of pulmonary tuberculosis (PTB) and lung cancer as comorbidities has been extensively discussed in many studies. In the past, it was well known that lung cancer is a specific epidemiological successor of PTB and that lung cancer often develops in scars caused by PTB. In recent years, the relevance of the two diseases has drawn attention in terms of the close epidemiological connection and chronic inflammation-associated carcinogenesis. In Japanese case series studies, most lung cancer patients with tuberculous sequelae received supportive care alone in the past, but more recently, the use of aggressive lung cancer treatment is increasing. Many studies on PTB and lung cancer as comorbidities have revealed that active PTB is noted in 2-5% of lung cancer cases, whereas lung cancer is noted in 1-2% of active PTB cases. In such instances of comorbidity, many active PTB cases showed Type II (non-extensively cavitary disease) and Spread 2-3 (intermediate-extensive diseases) on chest X-rays, but standard anti-tuberculosis treatment easily eradicates negative conversion of sputum culture for M. tuberculosis; lung cancer cases were often stage III- IV and squamous cell carcinoma predominant, and the administration of aggressive treatment for lung cancer is increasing. The major clinical problems associated with PTB and lung cancer as comorbidities include delay in diagnosis (doctor's delay) and therapeutic limitations. The former involves two factors of radiographic interpretation: the principles of parsimony (Occam's razor) and visual search; the latter involves three factors of lung cancer treatment: infectivity of M.tuberculosis, anatomical limitation due to lung damage by tuberculosis, and drug-drug interactions between rifampicin and anti-cancer drugs, especially molecularly targeted drugs. The comorbidity of these two diseases is an important health-related issue in Japan. In the treatment of PTB, the possibility of concurrent lung cancer should be kept in mind, while in the treatment of lung cancer, the possibility of concurrent PTB should also be considered.