QLTI-17. PROPHYLACTIC VANCOMYCIN REDUCES OMMAYA RESERVOIR-ASSOCIATED BACTERIAL MENINGITIS: A 12-MONTH PROSPECTIVE STUDY

Abstract

Abstract INTRODUCTION Intraventricular chemotherapy administered through an Ommaya reservoir (OR) constitutes the mainstay of therapy for adults with leptomeningeal metastases from solid and hematologic malignancies. Unfortunately, OR-associated bacterial meningitis remains a relatively frequent, costly, often morbid, and occasionally fatal complication, limiting the benefit of this approach. We investigated the potential efficacy, cost savings, and toxicity of intraventricular vancomycin co-administered with intraventricular chemotherapy. METHODS Detailed demographic, treatment, and outcome data were collected prospectively between 5/1/21 and 4/30/22 for 63 consecutive patients at our institution who underwent OR placement and subsequent intraventricular chemotherapy, co-administered with 10 mg of intraventricular vancomycin at each treatment. Reservoir-associated bacterial meningitis was defined as 2 consecutive positive cultures from the cerebrospinal fluid of the same organism or 1 positive culture in the presence of any other clinical or laboratory evidence of infection, or signs of infection at the surgical site. RESULTS The infection rate was 0% [95% CI 0-6.75%] among the 63 patients and 0% [0-0.76%] in the 501 consecutive treatments administered over the 12-month study period compared to 10.25% [7.39- 14.0%] in 322 patients and 1.71% [1.22-2.39%] in 1932 treatments over the preceding 5 years. The absolute risk reduction was 10.3% [3.83 - 14.04], p = 0.0049. The number needed to treat was 10 [7-26]. Cost per vancomycin dose was $10.00 ($5,010 over 12 months). The cost of non-surgical treatment of one OR-associated infection is $88,337.70, which translates into a $618,363.90 savings for the estimated 7 patients over 12 months spared an OR-associated infection. Savings were even further increased if OR removal and subsequent replacement was required. The only other covariate associated with (increased) infection risk on multivariable analysis was treatment number. No treatment-associated toxicity was observed. CONCLUSION Prophylactic intraventricular vancomycin eliminated OR-associated infection in patients receiving intraventricular chemotherapy. Dramatic cost savings were achieved without added toxicity.