Increased risk of active tuberculosis after cancer diagnosis.

BACKGROUND

Cancer may increase risk of active tuberculosis but evidence is sparse. We therefore examined tuberculosis risk in patients with incident cancer using Danish nationwide medical databases.

METHODS

We conducted a matched follow-up study comparing risk of active tuberculosis in cancer-exposed individuals to that in a general population comparison cohort, matched on gender, age, and country of origin, in different follow-up intervals using Cox regression.

FINDINGS: We identified 290,944 patients with incident cancer and 871,147 matched comparison cohort members during 1 January, 2004-30 November, 2013. After adjusting for comorbidities, the overall adjusted hazard ratio (aHR) for tuberculosis among cancer patients was 2.48 (95% confidence interval [CI]: 1.99-3.10). The highest tuberculosis risks were observed following cancers of the aerodigestive tract (aHR = 8.12; 95% CI: 4.33-15.22), tobacco-related cancers (aHR = 5.01; 95% CI: 3.37-7.44), and hematological cancers (aHR = 4.88; 95% CI: 2.27-10.48). Tuberculosis risk was highly elevated within the first year after cancer diagnosis (aHR = 4.14; 95% CI: 2.88-5.96), with a 6.78-fold increased aHR for cancer patients receiving cytostatics or radiotherapy. Beyond five years of observation, the overall aHR for tuberculosis remained at 2.66 (95% CI: 1.22-5.81).

INTERPRETATION: Cancer is a clinical predictor for increased risk of active tuberculosis, probably related to decreased infection barriers, immunosuppression, and shared risk factors.