People who've suffered from tuberculosis have a better chance of developing lung cancer, according to new research from Taiwan. Doctors have long noted that patients diagnosed with tuberculosis often go on to have other lung problems, even long after their TB is cured. But this is the first time a direct link between tuberculosis and an increased risk for lung cancer has been documented.
Epidemiologist John Sung from the China Medical University and Hospital in Taipei kept hearing from doctors in TB clinics that their patients frequently seemed to develop lung cancer. But no studies had examined the phenomenon. So, Sung obtained records from the country’s national insurance plan, to look for a link.
He selected one million sample patients out of 23 million from insurance data between 1990 to 2002. Of those million patients, Sung identified about 4,500 who had been diagnosed with tuberculosis. Then, he compared how many of the TB patients developed lung cancer over the subsequent decade as compared to the rest of the people in the data group who’d never had TB.
"We found that among of TB patients the incidence rate is 26.3 per thousand person-years, and for the general population is 2.4," says Sung. "So it's about 11 times higher in the TB patients than in the general population. It's really high."
Sung says it didn’t matter whether the TB patients were smokers, or had other risk factors for lung cancer. Just having had TB was enough. Sung also found that former tuberculosis patients were at increased risk for other potentially-fatal chronic lung diseases. The scale of the increase came as a surprise to the clinic doctors.
"According to observation, they knew TB patients have a high risk that they did not know how high," says Sung. "They did not expect that the incidence ratio is so high."
Sung's findings suggest doctors who treat tuberculosis should follow their patients after their TB is cured and they should be on the lookout for signs of lung cancer. Tuberculosis patients also need to continue being vigilant about their health so they can get treated earlier should they develop a problem.
Sung’s research is published in the Journal of Thoracic Oncology.