255. Breakthrough Mucormycosis (BT-MCR) on Antifungals Having Mucorales Activity Portrays Worse Prognosis compared with BT-MCR on Mold-Active Antifungals with no Mucorales Activity

Abstract

BackgroundBT-MCR is known to develop in the setting of agents having Aspergillus but no Mucorales activity. However, BT-MCR can occur even with the use of antifungals having with Mucorales activity in patients with hematologic malignancies and or stem cell transplant (HM).MethodsWe reviewed the records of HM patients treated for MCR (1994 to 2019) at MD Anderson Cancer Center. We identified patients with BT-MCR on antifungals having Mucorales activity: posaconazole (POSA), isavuconazole (ISA), and amphotericin B (AMB) (group A), and patients with BT-MCR on agents having Aspergillus but no Mucorales activity: voriconazole (VRC), itraconazole (ITZ), echinocandins (group B). BT-MCR was defined as MCR diagnosis (dx) after ≥7days (d) of antifungal use. The primary outcome was 42d mortality after the BT-MCR dx. Chi-square or Fisher’s exact test was used for categorical variables and Wilcoxon rank-sum test used for continuous variables. Cox regression model was used to evaluate the independent variables on outcome.ResultsWe identified 11 patients in group A (3 POSA, 5 ISA, 3 AMB) and 81 patients in group B (61 VRC, 13 echinocandins, 7 ITZ). Both groups were not different in terms of age, sex, underlying HM (AML/MDS in 100% vs. 88% in groups A and B, respectively), status of HM (active disease in 82% vs. 67%), prior stem cell transplant (45% vs. 54%) or GvHD (80% vs. 84%), neutropenia at dx (55% vs. 42%), prior receipt of >600 mg of prednisone (45% vs. 41%) or ICU at MCR dx (36% vs. 26%). Similarly, Mucorales species (Rhizopus spp. in 55% vs. 49%) and type of infection (sino-pulmonary in 73% vs. 68%) were no different between the groups. However, both d42 (82% vs. 46%, P = 0.025) and d84 (100% vs. 60%, P = 0.007) mortality was worse in group A. Similarly, median time to death was faster in patients in group A (26d, range 7-80d), vs. group B (42d, range 4–3146d, P = 0.031). Kaplan–Meier analysis showed a similar difference (Figure 1). In multivariate analysis, neutropenia (P = 0.038) and ICU at dx (P = 0.002) were independent factors on day 42d mortality in all 92 patients with prior Mucorales–active antifungals showing a trend associated with poor outcome (P = 0.17).ConclusionBT-MCR on agents having Mucorales activity is a marker of poor prognosis in HM patients. Early use of investigational immunotherapy and salvage antifungal chemotherapy studies is needed in that subgroup of patients. Disclosures All authors: No reported disclosures.