Since 2009 treatment of chronic ITP patients with thrombopoietin receptor agonists (TPO-RA) (romiplostim-eltrombopag) has been reimbursed in Belgium. Despite the initial assumption that this would be a life-long therapy, practical experience has shown that a significant number of patients do stop treatment. Reasons of TPO-RA discontinuation can be no efficacy, adverse events, ITP or non-ITP related death or spontaneous remission.  Spontaneous remission (SR) or treatment free-remission (TFR) is defined as a treatment-free period of  6 months (mo) with platelets  50000/l and no need of ITP rescue medication. 

We performed a survey to know how many patients were treated with TPO-RA (trial, reimbursed, medical need) and how many of these had stopped this treatment. More details were gathered of patients who discontinued treatment. The survey was sent by mail to all hematologists who were member of the Belgian Hematological Society.

20 Belgian centers participated in our survey and sent data. 
42 patients fulfilled the definition of SR or TFR, while 3 of these patients had several episodes of TFR. The baseline characteristics of the patients obtaining TFR were as follows:
26 patients were male and 16 were female; diagnosis of primary ITP was made in 34 patients; the 8 patients with secondary ITP had an underlying lymphoma (n=5), an Evans syndrome (n=2) or a previous transplant (n=1); mean age at ITP diagnosis was 50.5 years (y) (range 1-87y); median platelet count at ITP diagnosis was 5000/l; median time between ITP diagnosis and the start of TPO-RA was 5 y (range 1 mo-24y); at start of TPO-RA 5 patients fulfilled the definition of acute, 8 of persistent and 28 of chronic ITP; 54% (22/41) were splenectomized; 55% (22/40 ) needed  3 ITP treatments before the start of the TPO-RA (corticosteroids, intravenous immunoglobulins, rituximab, cyclophosphamide, cyclosporin, fansidar…); median platelet count at start of TPO-RA was 11000/l; median time on TPO-RA was 8 mo (range 0-74 mo); median platelet count was 267000/l at discontinuation of TPO-RA and 177000/l 6 m later. 
178 patients treated with TPO-RA (provided by 15 centers). Of these 100 patients discontinued treatment.  21% of the total cohort discontinued TPO-RA because of TFR and 37% of the discontinuations was due to TFR.  

Our survey confirmed that SR or TFR on TPO-RA is seen in about 20% of ITP patients treated in daily clinical practice in Belgium. TFR is seen not only in acute or persistent ITP but also in chronic ITP. TFR is seen in patients independent of splenectomy and independent of the number of treatments given before. In the future the incidence of TFR is thought to be even higher when the use of a forced tapering schedule will become common practice.

Treatment-free remission after TPO receptor agonists in adult ITP patients in Belgium