2381. Epidemiology of Clostridium difficile Infection in Patients Receiving Interleukin-2 Therapy

BACKGROUND: Clostridium difficile infection (CDI) has been associated with interleukin-2 (IL2) therapy, possibly leading to unnecessary testing and treatment of colonized patients receiving IL2 therapy. Since the debut of IL2 therapy for renal cell carcinoma (RCC) and metastatic melanoma (MM), only one study with 6 patients has shown a relationship between CDI and IL2 treatment, and no mortality data were reported. Because of the rising concern for appropriate testing and treatment of CDI, further studies looking at the correlation between IL2 therapy and CDI are needed. This study aims to describe CDI rates among a larger cohort of IL2 treated patients and to include mortality data. METHODS: Retrospective case series. A case of CDI was defined as (1) Bowel movements >3 or stool output >600 mL WITH, (2) positive laboratory test, either through toxin detection via ELISA prior to 2010 or molecular testing via PCR after 2010. RESULTS: During the study period from 2008 to 2015, 359 patients with RCC or MM receiving IL2 treatment were evaluated with a total of 294 patients undergoing Clostridium difficile testing (CDT). Median age was 52 (range 24–69), 33% female. An average IL2 dose of 27 million international units (MIU) was given in this population. 15% (45/294) had a positive CDT, but 7% (21/294) were found to have CDI. All patients with CDI had antibiotic exposure within the last 30 days of diagnosis. Of the patients who developed CDI, 24% (5/21) had a previous CDI episode within the last 90 days. None of the patients developed megacolon. Developing CDI lead to an all-cause mortality of 24% (5/21). CONCLUSION: The results of this study show a lower CDI rate (7%, 21/294) than previously reported in IL2-treated patients (66%, 4/6), but this difference is likely due to the difference in population size. In addition to CDI rate, this study adds information about mortality in IL2-treated patients with CDI, which was not previously described in the literature. Applying a clinical criterion to laboratory testing results revealed a difference in laboratory testing positivity and actual infection rates, suggesting 8% of this population maybe colonized with Clostridium difficile, providing further evidence for Antibiotic Stewardship Committees to put in place local guidelines to avoid indiscriminate CDT in this population. DISCLOSURES: All authors: No reported disclosures.