Incidence of and Risk Factors for Tuberculosis among Cancer Patients in Endemic Area: A Regional Cohort Study

BACKGROUND AND OBJECTIVE: Cancer is a known risk factor for developing active tuberculosis (TB) disease. The incidence of and risk factors for TB are not known among cancer patients in Thailand. This study aimed to investigate risk factors for TB among cancer patients in an area with endemic TB infections. METHODS: We used the Khon Kaen population–based cancer registry and two TB databases to conduct a retrospective cohort study of cancer patients. From 2001 to 2015, we identified 40,948 eligible cancer patients. Following until 2017, we identified cases of TB diagnosed after cancer diagnosis and analyzed primary cancer site, staging, treatment, and demographic factors. Adjusted incidence rate ratios (adj. IRR) were computed to identify risk factors among a sub–set of cancer types (n = 9,733) using Poisson regression. RESULTS: Among all cancer patients, 472 cases of TB were diagnosed following cancer diagnosis (cumulative incidence = 1.15%, incidence rate = 421.86 cases per 100,000 patients per year). Among the sub–set of cancer types, 206 cases of TB were found (cumulative incidence = 2.11%, incidence rate = 848.26 cases per 100,000 patients per year). Risk factors for TB among cancer patients were sex (p < 0.001) (male adj. IRR = 1.87, 95% CI: 1.36–2.59), age (p < 0.001) (age >70 adj. IRR = 2.36, 95% CI: 1.56-3.55, compared to age ≤50) and cancer site (p < 0.001). Compared to thyroid cancer, TB infection was more associated with lung cancer without histopathological confirmation (adj. IRR = 6.22, 95% CI: 2.57–15.04). Cancer stage and treatment did not show statistically significant trends. CONCLUSION: Old age, male sex, and certain cancer types were independent risk factors for TB in cancer patients. Targeted latent TB screening may be appropriate among high risk groups.