Risk of Active Tuberculosis Higher After Cancer Diagnosis.
Cancer patients—especially those with cancers of the aerodigestive tract and hematological and tobacco-related cancers—are at increased risk of active tuberculosis, with elevated rates among those receiving radiotherapy or cytotoxic drugs, according to a new Denmark-based study co-authored by School of Public Health researchers.
The findings, published in the Journal of Infection, lend support to the theory that cancer is a clinical predictor for increased risk of active tuberculosis (TB), probably due to decreased infection barriers, immunosuppression, and shared risk factors.
“Our nationwide population-based cohort study provides strong evidence that cancer is associated with increased risk of active TB,” the study says. “While risk of TB was highest in the period immediately before and after a cancer diagnosis, it remained elevated beyond five years of follow-up.”
The research team, from SPH and Aarhus University Hospital in Denmark, used data on cancer diagnoses from the Danish Cancer Registry from 2004 to 2013 and on active TB, during the same years, from the Danish National Patient Registry.
Cancer patients were particularly at increased risk of TB shortly after diagnosis, the study found. Within the first year after diagnosis, the adjusted relative risk of TB was 4.14 higher; between one and five years of follow-up, it was 1.70.
Particularly high risks of TB were observed for cancers of the aerodigestive tract (8.12 times the risk), tobacco-related cancers (5.01 times), and hematological cancers (4.88 times).
The researchers said the high relative risk of TB shortly after a cancer diagnosis was consistent with the hypothesis that cancer renders patients susceptible to new TB infections or reactivation of a “previously contained focus of TB.”
Cytotoxic drugs and radiotherapy treatments further increase those risks because of the likely “additive effect of cancer treatment on cancer-induced susceptibility to reactivation of LTBI (latent TB infection),” the researchers said. They said that screening for LTBI before initiation of chemotherapy could be useful for people with cancer, particularly those with other risk factors for LTBI, such as alcoholism or drug abuse.
SPH co-authors on the study include: Robert Horsburgh, professor of epidemiology; and Henrik Sorensen, adjunct professor of epidemiology. The study was led by Dennis Simonsen of Aarhus University Hospital.