Prognostic Parameters For Remission Of and Survival In Acquired Hemophilia A: Results Of The GTH-AH 01/2010 Multicenter Study

Acquired hemophilia A (AHA) is a rare autoimmune disorder caused by neutralizing autoantibodies against coagulation factor VIII (FVIII:C). Immunosuppressive treatment may result in remission of disease over a period of days to months. Until remission, patients are at high risk of bleeding and complications from immunosuppression. Prognostic parameters to predict remission and the time needed to achieve remission could be helpful to guide treatment intensity, but have not been established so far. GTH-AH01/2010 was a prospective multicenter cohort study using a standardized immunosuppressive treatment protocol. The primary study endpoint was time to achieve partial remission (PR, defined as FVIII:C activity >50 IU/dl after cessation of any hemotherapy for >24h, and no active bleeding). Secondary endpoints were time to achieve complete remission (CR, defined as PR plus negative FVIII:C inhibitor, steroid tapered to <15 mg/d prednisolone, and cessation of any other immunosuppressive treatment), and overall survival (OS). Enrolment was strictly prospective and only allowed within 7 days of starting immunosuppression. Outcome data were recorded in all patients enrolled. The treatment protocol consisted of prednisolone (100 mg/d from day 1 to the day of PR, then tapered down to <15 mg/d over 5 weeks), oral cyclophosphamide (150 mg/d, from day 21-42, unless PR was achieved), and rituximab (375 mg/m² weekly for 4 weeks starting on day 43, unless PR was achieved). If AHA was first diagnosed in patients previously on prednisolone >15 mg/d, or equivalent, they received prednisolone (100 mg/d) and rituximab from day 1. If cyclophosphamide was contraindicated, patients received prednisolone (100 mg/d) and rituximab from day 21. One hundred twenty-four patients from 21 treatment centers in Germany and Austria were enrolled between April 2010 and April 2013 (36 months). The patients from two centers not compliant with the treatment protocol were excluded (N=18), as were patients in whom AHA was not confirmed (N=2) or follow-up was too short at the time of this analysis (N=7). The remaining 97 patients from 17 centers were followed for a median of 256 days (interquartile range [IQR] 84-561). Median age was 74 years (IQR 64-82). AHA was associated with other autoimmune disorders (19%), malignancy (12%), pregnancy or puerperium (5%), but was most often idiopathic (66%). The median FVIII:C activity at baseline was 1 IU/dl (IQR <1-3), and the median inhibitor titer was 20 BU/ml (IQR 7.7-78). PR and CR were achieved after a median time of 35 and 102 days, respectively. Patients achieving PR prior to day 21 (N=22) compared with patients not achieving PR within 21 days (N=75) had a higher baseline FVIII:C activity (median 3 vs. <1 IU/dl, p<0.01) and a lower FVIII:C inhibitor (median 12 vs. 29 BU/ml, p<0.05). Multivariate analysis with adjustment for age, sex, underlying disorder, and WHO performance status on admission demonstrated that baseline FVIII:C activity (<1 IU/dl vs. >=1 IU/dl) had a strong impact on the time to achieve PR (HR 2.76 [95% confidence interval 1.73-4.42], p<0.001) and CR (HR 2.36 [1.34-4.14], p<0.01). Baseline FVIII:C activity was also a predictor of PR and CR when other cutoffs were used (2 or 3 IU/dl instead of 1 IU/dl), or when it was analyzed as a continuous variable in Cox regression analysis. In contrast, FVIII:C inhibitor titer assessed by the local laboratory did not affect time to PR or CR significantly. OS after 300 days, estimated by the Kaplan Meier method, was 69%. Age, WHO performance status, and FVIII:C activity at baseline were independent predictors of OS. In summary, GTH-AH 01/2010 is the largest prospective study of patients with AHA treated according to a standardized protocol. The study demonstrated a robust effect of baseline FVIII:C activity on the time needed to achieve PR and CR. Baseline FVIII:C activity, together with age and performance status, also affected OS. Therefore, baseline FVIII:C activity may be considered to guide individually tailored immunosuppression in future studies.