The following article features coverage from the 61st American Society of Hematology Annual Meeting and Exposition. Click here to read more of Hematology Advisor’s conference coverage.

The addition of rituximab to corticosteroid treatment of first immune thrombotic thrombocytopenia (iTTP) episode may not prevent relapse in the long term, according to research presented at the 61st American Society of Hematology (ASH) Annual Meeting in Orlando, Florida.

Rituximab is commonly used to treat patients with relapsed or refractory iTTP, but use of rituximab to treat first episodes of iTTP has become more frequent. Researchers retrospectively analyzed patient data from the United States Thrombotic Microangiopathy Consortium’s iTTP registry to determine whether the addition of rituximab to treatment with corticosteroids leads to improvements in relapse-free survival (RFS).

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Data were available for 775 patients, 362 of whom were treated for first episode of iTTP. Of those patients, 188 received corticosteroids alone, 131 received cortiocosteroids and rituximab, and 56 received other treatment agents. RFS was calculated using Kaplan-Meier curves.

Overall, patients who had received rituximab experienced improved RFS at 1 year (0.93 vs 0.78; P =.0002) and 3 years (0.82 vs 0.66; P =.004) after treatment compared with patients who had received only corticosteroids. However, after 5 years of treatment, there was no significant difference in RFS between the groups (0.60 vs 0.56; P =.39). In patients with relapsed disease, RFS did not significantly differ between those who received rituximab and those who did not (0.43 vs 0.47; P =.76).

Risk for relapse decreased over time in accordance with rituximab use. RFS was inferior in de novo African American patients compared with de novo Caucasian patients regardless of treatment regimen (hazard ratio [HR], 1.83; P =.02). In addition, the researchers found that adding rituximab to treatment led to improvements in RFS in Caucasian patients (HR, 0.15; P <.0001) but not in African American patients (HR, 1.15; P =.43), suggesting a significant association between treatment and race (P =.0007).

Following this analysis, the researchers created a severity scoring system to account for selection bias, as they hypothesized that “patients with more severe disease were more likely to receive rituximab.” Though they did find evidence of selection bias, adjusting for this bias did not yield any changes in their findings.

“Rituximab appears to delay relapse a few years, but it doesn’t change the overall trajectory of the disease,” concluded Marshall A Mazepa, MD, of the University of Minnesota in Minneapolis. Future directions for research, he added, should address why African American patients “appear to have a different natural history than Caucasian patients” and should explore “alternative immunosuppression in patients who [do not] respond to rituximab.”

Disclosures: Some authors have declared affiliations with the pharmaceutical industry. Please refer to the original study for a full list of disclosures.

Reference

  1. Marshall MA, Evans M, Davis E, et al. Differential effect of rituximab on relapse-free survival in de novo and relapsed immune thrombotic thrombocytopenic purpura in African-American and Caucasian populations. Oral presentation at: 61st ASH Annual Meeting and Exposition; December 7-10, 2019; Orlando, FL. Abstract 90.