Johns Hopkins University School of Medicine researchers are harnessing the power of CT and PET imaging in a bid to improve how tuberculosis is treated.
Using the visualization capabilities of both modalities combined, the group was able to noninvasively measure the effectiveness of a key drug used to treat TB: rifampin. Their approach, detailed Feb. 17 in Nature Medicine, showed that the agent is not attacking the specific areas necessary to defeat the deadly infection.
"This is eye-opening since the lesions and cavities are the sites known to have the largest populations of bacteria in TB patients," Alvaro Ordonez, MD, a pediatrics researcher at the Baltimore-based university, said in a statement. "Therefore, rifampin is not getting where we need it most."
A central problem in treating TB is mycobacterium infectious agents, which carve cavities into the lungs to protect itself from being killed by therapeutic drugs. This process destroys cells and blood vessels while building up scar tissue in the surrounding area. After this occurs, delivering anti-tuberculosis drugs through the bloodstream becomes more difficult.
And until this most recent trial, the only way clinicians could tell if rifampin was even working is if they analyzed surgically removed portions of the lung from patients who didn’t respond to standard therapy. There are a number of drawbacks to this approach, the authors noted, including the fact that it is invasive.
For their study, Ordonez and colleagues injected 12 patients with a microdose of 11 C-rifampin—an agent that emits charged particles and enables clinicians to track the TB-fighting drug during imaging. After determining that this dose could accurately represent how a standard clinical dose would behave, they analyzed the patient’s PET imaging data.
The scans showed that 11 C-rifampin uptake was lowest in the lesions and cavities caused by TB. In fact, it was less than half of the amount recorded in healthy lung tissue. By using this data, investigators hypothesized that increasing a patient’s dose of rifampin could reduce the time required to treat TB from six months down to four.
"This would have a dramatic impact on the worldwide fight against TB," Sanjay K. Jain, with Johns Hopkins’ Center for Tuberculosis Research, said in a statement. "We hope that the tool will one day enable clinicians to determine the most effective doses of specific drugs in specific patients, so as to further optimize the treatment of infectious diseases," Jain added.