NEW YORK (Reuters Health) – Fidaxomicin, approved by the US Food and Drug Administration in 2011 for the treatment of Clostridium difficile-associated diarrhea, is particularly effective in cancer patients, a multicenter study has shown.

“For patients with cancer, fidaxomicin treatment was superior to vancomycin, resulting in higher cure and sustained response rates, shorter TTROD (time to resolution of diarrhea), and fewer recurrences,” the researchers found.

Dr. Oliver A. Cornely, with the University Hospital of Cologne, Germany, and colleagues explain that the incidence of C. difficile-associated diarrhea (CDAD) is six time higher among oncology patients than other hospitalized patients. To compare treatment with vancomycin or fidaxomicin in this population, the team analyzed data from two double-blind randomized trials.

Among a total of 1105 patients with CDAD, 183 had solid tumors or hematologic malignancies. Overall, cure rates were lower among the cancer patients (79.2%) than in the other patients (88.6%; p<0.001), the investigators found.  Also, the median TTROD in the two groups was 100 hours versus 55 hours, respectively.

Looking at differences between treatment arms, cure rates for patients without cancer were similar with fidaxomicin or vancomycin (88.5% versus 88.7%; p=0.913). However, for cancer patients, the cure rate was better with fidaxomicin (85.1%) than vancomycin (74.0%; p=0.065)

Similarly, the median TTROD among patients without cancer was 54 hours with fidaxomicin and 58 hours with vancomycin, while corresponding times among the cancer group were 74 hours versus 123 hours.

The risk of recurrence was approximately double with vancomycin rather than fidaxomicin treatment, whether or not patients had cancer, according to the report in the Journal of Clinical Oncology online May 28. “However, because both cure and recurrence outcomes were improved in the fidaxomicin arm as compared with the vancomycin arm in patients with cancer, the relative odds of sustained response at 28 days in patients with cancer were more than 2.5-fold for fidaxomicin versus vancomycin (OR=2.56; p=0.003),” the authors point out.

Regarding safety for patients with cancer, 85.3% of those receiving fidaxomicin had at least one adverse event compared to 83.5% of those treated with vancomycin.

Dr. Cornely and colleagues caution that their analysis was conducted post hoc, and the studies were not designed to look specifically at efficacy in patients with cancer. “Despite these limitations,” they concluded, “the results are promising and support the conduct of additional studies within cancer populations.”

As they point out, “Earlier resolution of diarrhea combined with a high probability of sustained response can potentially avoid delays in cancer therapy.”

SOURCE: Resolution of Clostridium difficile–Associated Diarrhea in Patients With Cancer Treated With Fidaxomicin or Vancomycin
J Clin Oncol 2013;31.