Last Updated: 2009-11-17 16:00:14 -0400 (Reuters Health)

NEW YORK (Reuters Health) – Tuberculosis (TB) appears to be linked to an increased risk of lung cancer, particularly adenocarcinoma, according to a meta-analysis appearing in the December 15th International Journal of Cancer.
Senior author Dr. Bao-Sen Zhou of China Medical University, Shenyang and colleagues observe that a number of retrospective studies have suggested a relationship between pre-existing TB and lung cancer, but findings have been inconsistent.

To investigate further, the researchers examined data from 37 case-control studies and 4 cohort studies that together involved more than 19,000 cases and 118,000 controls.
Their meta-analysis of risk estimates found a significantly increased lung cancer risk associated with pre-existing TB. This was not due to confounding effects of tobacco use, the authors said. In fact, the relative risk in never smokers was 1.8.

In studies that controlled for smoking, the relative risk of lung cancer with TB was 1.74. After adjusting for lifetime environmental tobacco smoke exposure, this rose to 2.93.
Pooled estimates for adenocarcinoma showed a significant association (relative risk, 1.60) with a history of TB. There were no significant associations between TB and squamous cell or small cell lung cancer, however.

The researchers conclude by pointing out that "increased lung cancer risk appeared greatest within the first 5 years after TB diagnosis, but the risk for lung cancer remained 1.99-fold elevated for more than 20 years after TB diagnosis."

Int J Cancer 2009;125:2936-2944.