Encouraging findings, lingering concerns
Nicholas Turner, MD, assistant professor in the division of infectious diseases at Duke University, Durham, N.C., praised the study for “pushing the boundaries for FMT,” and noted that the methodology appeared sound. Results in the placebo group, however, cast doubt on the generalizability of the findings, he said.
Dr. Nicholas Turner
“If you look at the group that received vancomycin plus placebo, their failure rate was really astoundingly high,” Dr. Turner said in an interview, referring to the 67% failure rate in the control group; he noted previous studies had reported failure rates closer to 10%. “I think that just calls into question just a little bit what happened with that control group.”
Dr. Turner said his confidence would go “way, way up” if the findings were reproduced in a larger study. Ideally, these future trials would use fidaxomicin, he added, which is becoming the preferred option over vancomycin for treating C. difficile.
John Y. Kao, MD, professor of medicine and codirector of the FMT program at University of Michigan Medicine, Ann Arbor, offered a different perspective, suggesting that the control group findings shouldn’t overshadow the efficacy of FMT.
“I agree that historical data would tell us that the placebo population should see a much higher response,” Dr. Kao said in an interview. “In my mind though, the success rate of FMT over placebo is what I would expect. The message of the study should be upheld: that FMT is an effective therapy whether it’s given early or, as the way we give it now, as a sort of rescue therapy.”
Dr. John Y. Kao
Despite this confidence in FMT as an efficacious first-line option, Dr. Kao said it is unlikely to be routinely used in this way anytime soon, even if a larger trial echoes the present results.
“We don’t know the long-term risks of FMT therapy, although we’ve been doing this now probably close to 20 years,” Dr. Kao said.
Specifically, Dr. Kao was most concerned about the long-term risk of colon cancer, as mouse models suggest that microbiome characteristics may affect risk level, and risk may vary based on host-microbiome relationships. In other words, an organism may pose no risk in the gut of the donor, but the same may not be true for the recipient.
While increased rates of colon cancer or other serious illnesses have not been detected in humans who have undergone FMT over the past 2 decades, Dr. Kao said that these findings cannot be extrapolated over a patient’s entire lifetime, especially for younger individuals.
“In a patient that’s 80, you would say, yeah, let’s go ahead and treat you [with FMT] as first-line therapy, whereas someone who’s 20, and has maybe another 50 or 60 years longevity, you may not want to give FMT as first-line therapy,” Dr. Kao said.
This study was supported by Innovation Fund Denmark. The investigators disclosed no competing interests. Dr. Turner previously performed statistical analyses for a Merck study comparing vancomycin, fidaxomicin, and metronidazole for C. difficile infection. Dr. Kao disclosed no relevant conflicts of interest.