PF690 PREDICTORS OF THERAPY FREE RESPONSES IN ITP PATIENTS RECEIVING TPO‐RA. RESULTS FROM A SPANISH MULTICENTER STUDY

Abstract

Background:Thrombopoietin receptor agonists (TPO‐RA) are a well‐established treatment in patients with primary immune thrombocytopenia (ITP). Sustained treatment‐free responses (TFR) after TPO‐RA discontinuation in adult ITP have been reported; yet, to date there are no predictors to identify in which patients this approach is likely to be successful.Aims:To evaluate clinical predictors of TFR in a real world cohort of ITP patients treated with TPO‐RA.Methods:Patients aged >18 years with primary ITP who had initiated TPO‐RA (eltrombopag [EPG] or romiplostim [ROM]) treatment between January 2012 and December 2014 were included in this retrospective, multicenter study from 19 secondary and tertiary Spanish hospitals. Data on patient characteristics, history of disease and previous therapies, TPO‐RA administration, response and discontinuation were collected from medical records.Results:A total of 121 patients with a median age of 63 years (range 19–96 years), 59% females initiated TPO‐RA as long‐term therapy (ROM 54; EPG 67). Sixty‐eight percent of the patients treated with TPO‐RA met criteria for chronic, 16% for newly diagnosed and 16% for persistent ITP. The median time on TPO‐RA treatment was 35.2 months (1 to 67.3 months), and the median follow‐up from start of TPO‐RA until collection of data was 44.9 months (23.8 to 67.5 months). A total of 39 patients (32.2%) switched TPO‐RA during follow‐up. The most frequent cause for switching was lack of efficacy (48.7% of cases ‐in 89.5% the initial TPO‐RA was EPG‐). Due to switching the exposure to both TPO‐RAs was similar during follow‐up; 80 patients received ROM and a similar number was treated with EPG, with total exposure (years) of 161.0, and 168.3, respectively.During follow‐up almost one half of the patients (46.3%, n = 56) tapered‐off the TPO‐RA; 10 out of the 37 cases that discontinued ROM had previously received EPG, and 4 out of the 19 that stopped EPG had switched from ROM. After a median of 432 days (29–1344) under TPO‐RA treatment, 35 patients (28.9%) maintained TFR defined as platelet counts >50x109/l for more than 6 months. In 4 of these 35 cases, TPO‐RAs were reintroduced due to loss of response after a median TFR of 20.5 months. Potential predictors of TFR in the remaining 31 patients (25.6%) with sustained platelet counts in the absence of any agent meant to increase platelet count (median 32 months, 8–217) were analyzed. No specific patient feature (e.g. age, comorbidities, ITP duration, previous treatments), bleeding, previous therapies nor phase of disease seemed to consistently predict for sustained response off therapy. However, univariate analysis (Chi‐square) did identify statistically significant predictors of TFR. Interestingly, while the specific TPO‐RA that was discontinued did not influence the probability to achieve TFR, receiving ROM as first TPO‐RA was positively associated with TFR (P = 0.010), while switching TPO‐RA negatively predicted sustained platelet responses (P = 0.002). In multivariate analysis with logistic regression both variables predicted significantly higher odds of TFR (Table 1).Summary/Conclusion:Platelet response following TPO‐RA cessation is sustained in 25.6% of adult patients with primary ITP. Although published studies have not identified a predictive factor of sustained response after TPO‐RA discontinuation, in this long‐term follow up analysis, ROM as first TPO‐RA being administered, and no need of TPO‐RA switching are factors that positively correlate with the probability to achieve TFR.image