Low-dose rituximab in adult patients with primary immune thrombocytopenia

Rituximab 375 mg/m(2) weekly for 4 wks has significant activity in adults with primary immune thrombocytopenia (ITP). In this setting, several evidences support the possible use of lower doses of rituximab.

To investigate the activity of low-dose rituximab as salvage therapy in previously treated symptomatic ITP.

Forty-eight adult patients were treated prospectively with rituximab 100 mg weekly for 4 wks.

Overall and complete responses (CR) (platelet level ≥ 50 and 100 × 10(9) /L) were 60.5% and 39.5%, respectively. In responders, the median time to response was 35 d (range: 7-112 d). The median time of observation was 18 months (range 3-49 months). Sixteen of 29 responding patients (55%) relapsed and 14 needed further treatments. The 12- and 24-month cumulative relapse-free survival was 61% and 45%, respectively. In univariate analysis, CR rate was in inverse relation with weight OR=0.95, CI(95%) [0.91; 0.99] (P=0.019) and age OR=0.96, CI(95%) [0.93; 0.99] (P=0.047). Cox regression model showed that relapse probability increases as weight (HR=1.06, CI(95%) [1.0031; 1.111]) and period between diagnosis and rituximab therapy (HR=1.01, CI(95%) [1.002; 1.017]) increase. One patient developed an interstitial pneumonia 1 month after the end of rituximab treatment. No other infectious, hematologic or extra-hematologic complications were documented during follow-up.

Low-dose rituximab is active in ITP but has moderate long-term effect. A comparative study with standard dose is warranted.