TB Associated With Increased Lung Cancer Risk, Study Says

Contracting tuberculosis is associated with an increased risk of developing lung cancer in rural China, according to a study published in the March issue of the International Journal of Cancer, Reuters Health reports. According to lead author Eric Engels of the National Cancer Institute, tobacco and indoor air pollution are "major causes" of lung cancer in Xuanwei County, China. He said researchers have proposed that TB could "increase the risk of lung cancer because of lung inflammation and fibrosis that could induce genetic damage."

For the study, Engels and colleagues used data from a retrospective cohort study involving 42,422 farmers in Xuanwei. They tracked the association between TB and lung cancer risk among the subjects from 1976 to 1996. In 1992, the participants completed questionnaires that included questions about demographics, household characteristics and lifetime medical history. During the study period, 246 subjects, or 0.6%, reported contracting TB. In addition, 2,459 participants, or 5.8%, died of lung cancer, including 31 of the 246 people who had TB.

The researchers determined that the hazard ratio for lung cancer mortality was 6.1 for subjects who contracted TB. In addition, they concluded that the association between TB and lung cancer risk was especially high during the first five years after TB diagnosis, when hazard ratios ranged from 6.7 to 13. The hazard ratio remained significant at 3 for 10 years after TB diagnosis, the study said. The researchers also found that associations between TB and lung cancer were similar among men and women.

The researchers write that their findings support the "possibility that [TB] may act through a process of localized pulmonary inflammation and fibrosis to initiate or promote the development of lung cancer, particularly in conjunction with other carcinogenic exposures." In addition, they write that the potential relationship between TB and lung cancer development "points to the continuing need to develop and implement improved [TB] prevention and treatment programs, especially in the developing world" (Reuters Health, 3/12).

An abstract of the study is available online.