Non-pulmonary cancer risk following tuberculosis: a nationwide retrospective cohort study in Lithuania.

Background: Lithuania remains one of the highest tuberculosis burden countries in Europe. Epidemiological studies have long pointed to infections as important factors of cancer aetiology, but the association between tuberculosis and the risk of non-pulmonary cancers has rarely been tested and results have been inconsistent. The aim of this population-based cohort study was to examine the risk of cancer among patients diagnosed with tuberculosis using data from Lithuanian Tuberculosis, Cancer and Resident's Registries.

Methods: The study cohort included 21,986 tuberculosis patients yielding 1583 cancers diagnosed during follow-up (1998-2012). Standardized incidence ratios (SIRs) and 95% confidence intervals (95% CIs) were calculated to compare the incidence of cancer among cohort participants with the general population for overall, non-pulmonary, site-specific cancers, as well as for subgroups of smoking-related, alcohol-related, hormone-related and haematological cancers.

Results: The SIRs of all cancers combined were 1.89, 95% CI: 1.79-2.00 in men and 1.34, 95% CI: 1.19-1.50 in women. Risk was increased 3-fold within the first year following diagnosis; it decreased during later years, although remained significantly elevated for ≥5 years. Elevated long-term increased risks persisted for non-pulmonary cancers overall, and for cancers of mouth and pharynx, oesophagus, stomach, larynx, cervix uteri and leukaemias. Tuberculosis was associated with a decreased risk of melanoma. Increased risks were observed for smoking-related cancers in men (SIR 1.95, 95% CI: 1.79-2.13) and women (SIR 1.46, 95% CI: 1.22-1.73), alcohol-related cancers in men (SIR 2.40; 95% CI: 2.14-2.68) and haematological cancers in men (SIR 1.73, 95% CI: 1.33-2.23). The risk of hormone-related cancers was 18% lower (SIR = 0.82, 95% CI: 0.66-0.997) among women, the inverse association was weaker among men (SIR = 0.95, 95% CI: 0.84-1.07).

Conclusions: The risk of total and several non-pulmonary cancers was elevated in a cohort of tuberculosis patients. The recommendation for the awareness of this association among physicians is warranted. Analysis suggests a reduction in risk of hormone-related cancers and melanoma.