Early Increased Platelet Count Is a Predictive Factor for a Long-Term Response in High-Dose Dexamethasone Treatment for Newly-Diagnosed Immune Thrombocytopenia Patients.

Background: Immune thrombocytopenia (ITP) is an autoimmune disorder characterized by increased destruction of platelets. Guidelines recommend corticosteroids with or without intravenous immunoglobulin as an initial therapy for ITP patients who are required treatment. Prednisone (or predonisolone) has been widely used as a first-line treatment. High-dose dexamethasone (HD-DXM) is an alternative corticosteroid for prednisone. Recently, a randomized clinical trial, in which four-days HD-DXM was compared with standard prednisone in newly diagnosed ITP patients. The results showed that higher remission rate was obtained in patients treated with four -days HD-DXM, suggesting that HD-DXM is preferred in certain ITP patients. However, long-term outcomes of the patents treated with HD-DXM has not been fully evaluated. In this study, we retrospectively analyzed ITP patients who received HD-DXM as initial therapy to evaluate a long-term efficacy of HD-DXM and to find out predictive factors for long-term response.

Patients and methods: We reviewed clinical records of patients who were diagnosed as ITP from Aug 2005 to Feb 2015 in Tokyo Women's Medical University Hospital. Patients who received HD-DXM because of a platelet count of less than 20,000 per cubic millimeter or a platelet count less than 50,000 per cubic millimeter with clinically significant bleeding, were included this study. An initial response was defined as an increase number of platelets, 30,000 per cubic millimeter or more and at least 2-fold increase of the baseline count and absence of bleeding between day 8-18 days after HD-DXM. Sustained response was defined as follows: platelet count was maintained 30,000 per cubic millimeter or more and absence of bleeding after achievement of initial response.

Results: A total of 30 patients were analyzed in this study. Median age of patients was 63 years (range, 23 to 91). The mean platelet count before treatment was 11,000 (range, 2,000 to 50,000) per cubic millimeter. Median follow up period is 35 months (range, 0.7 to 129.5). Dexamethasone (30-40mg per day) was administrated for 4 days for 1-3 cycles. Initial response was obtained in 17 of 30 patients (56.7 %). In responder group (n=17), sustained response rates at 6, 36, and 60 months was 92.8% (13/14), 87.5 % (7/8), and 100 % (6/6). Among non- responders within 18 days (n=13), long-term response rates at 6, 36, and 60 months was 58.3% (7/12), 100 % (3/3), and 100 % (2/2). We investigate clinical characteristics of the patients obtained long-term response, including duration of HD-DXM, age, platelet count before HD-DXM, lymphocyte count before HD-DXM, number of HD-DXM, to find out predictive factors for long-term response. In some patients obtained long-term response, early increase platelet count within a week was observed. Interestingly, among non-responders, early increased platelet count within a week was observed in seven patients, and five of these seven patients (71.4%) obtained response at six months. In a logistic regression model, univariable and multivariable analysis indicates early increased platelet count within a week after initiation of HD-DEX was significantly efficacy associated with long-term response (P=0.02, P=0.01, respectively).

Conclusion: In this study, HD-DXM is an effective initial therapy for ITP patients. Long-term response was obtained in substantial number of patients. The present result suggests that increased platelet count within a week after HD-DXM initiation predicts long-term response.