Venous Thromboembolism Incidence and Risk Factors in Patients Undergoing Hematopoietic Stem Cell Transplantation.

Malignancy is a well-known risk factor for venous thromboembolism (VTE), and the Khorana risk score is effective for screening patients with solid tumors. However, there is a lack of validated screening tools and established risk factors for patients undergoing hematopoietic stem cell transplantation (HCT). Current literature reports a 2.5% to 8.5% incidence of VTE in HCT recipients. Anticoagulation is difficult to manage post-transplantation, given prolonged thrombocytopenia and the likelihood of bleeding. By identifying risk factors, a predictive model may be developed to prospectively test prophylaxis strategies in patients at the highest risk of a thromboembolic event (TE). This retrospective single-center study evaluated the cumulative incidence of TE at 6 months following allogeneic or autologous HCT in adult subjects undergoing transplantation between March 2014 and December 2019. The study also aimed to identify risk factors for developing a TE, evaluate the time from HCT to TE, and compare 1-year survival following HCT between patients with a TE and those without a TE. In evaluating the incidence of TE, ICD-9 and ICD-10 codes were used to determine cancer diagnosis, TE events occurring up 180 days after HCT, and comorbidities of interest. Each subject was reviewed for data accuracy by a manual retrospective chart review. Statistical tests including the cumulative incidence method with competing risks, Gray's test, and univariate and multivariate Cox proportional hazards models were used to analyze the time to first TE, evaluate risk factors, and assess 1-year survival post-HCT in relation to TEs occurring within 180 days of HCT. Variables examined included age, sex, body mass index, transplant type, hospital length of stay (LOS), history of TE prior to transplantation, active infections, graft-versus-host disease (GVHD), veno-occlusive disorder, cytomegalovirus serostatus, and other factors. The study included 636 evaluable patients; the majority were male (57.9%) and white (68.7%) and had undergone autologous HCT (68.4%). Twenty-nine patients (4.6%) experienced a TE within 180 days post-transplantation. TEs were more common in the allogeneic HCT recipients (n = 13/201; 6.5%) compared to the autologous HCT recipients (n = 16/435; 3.7%; P = .122). The cumulative incidence of TE was higher in patients who developed an active infection compared to those who did not (7.6% versus 3.1%; P = .011). Hospital LOS (hazard ratio [HR], 1.03; 95% confidence interval [CI], 1.0 to 1.06; P = .036) and active infection (HR, 2.34; 95% CI, 1.1 to 4.95; P = .027) were significantly associated with TE in univariate analysis but were not retained in the final multivariate model. There was no difference in 1-year survival between all patients who experienced a TE and those who did not; however, in the autologous HCT group, 1-year survival rate was significantly lower in patients with a TE compared to those without TE (80.4% versus 95.3%; P = .01) (Figure 3C). None of the examined variables, including a history of TE and GVHD, were associated with TE risk. Although the overall incidence of TE in our study was low, many patients received pharmacologic or mechanical prophylaxis, suggesting that such strategies may be effective in mitigating TE risk. Such factors as infection and hospital LOS may further increase TE risk. Providers should continuously monitor for risk factors and signs and symptoms of TE post-transplantation. It is also imperative to consider chemical prophylaxis if counts are recovered during hospitalization.