2646. Incidence of Myelosuppression Related to Valganciclovir Prophylaxis in Solid-Organ Transplant Recipients at High Risk of CMV Disease

Background Valganciclovir (VGCV) prophylaxis in solid-organ transplant patients (SOT) is limited by myelotoxicity. We aimed to analyze the impact of VGCV prophylaxis on myelotoxicity and risk factors for its occurrence. Methods Retrospective single-center cohort study of adult CMV-seronegative recipients transplanted between July 2005 and November 2017. CMV D+/R− recipients received 3 to 6 months of VGCV prophylaxis whereas CMV D-/R- received no VGCV. Definitions: leukopenia < 3.5 × 109/L, significant neutropenia < 1.0 × 109/L and significant thrombocytopenia < 50 × 109/L. Results A total of 363 SOT recipients were included, 169 (47%) CMV D+/R− and 194 (53%) CMV D−/R−, with a mean age of 49.5 years and 275 (76%) males; types of organ transplant: 133 (37%) liver, 181 (50%) kidney, 37 (10%) simultaneous kidney-pancreas and 12 (3%) other. Although there was no difference in the incidence of significant neutropenia or thrombocytopenia per transplant type, leukopenia in the first year was more common in liver transplant patients (P < 0.001). New onset leukopenia post-SOT, significant neutropenia (Figure 1) and significant thrombocytopenia in the first year were more common in patients receiving VGCV: 116 D+/R− (69%) vs. 52 D−/R− (31%), P < 0.001; 86 (91%) vs. 9 (9%), P < 0.001; 8 (80%) vs. 2 (20%), P = 0.050; respectively. G-CSF was used more frequently in patients receiving prophylaxis (60% CMV D+/R− vs. 10% CMV D−/R−, P < 0.001). Significant neutropenia had no impact on long-term mortality adjusted by age and transplant type (HR 1.1, 95% CI 0.6–2.1, P = 0.709). Significant neutropenia led to decrease immunosuppression in 90% of patients (vs. 46%, P < 0.001) and was associated with increased risk of rejection (HR 8.5, P < 0.001). In multivariate analysis for significant neutropenia in the first year, VGCV prophylaxis was the only predictor of this outcome after adjusting for confounders (HR 15.1, 95% CI 7.5–30.1, P < 0.001). Conclusion VGCV prophylaxis increased the risk of significant neutropenia by 15-fold post-SOT. No other clinical variables were useful to predict this complication. Therefore, complete blood count monitoring is still needed for all SOT recipients receiving VGCV prophylaxis. Disclosures All authors: No reported disclosures.