Long-term follow-up of a prospective phase 2 clinical trial of extended treatment with rituximab in patients with B cell post-transplant lymphoproliferative disease and validation in real world patients

The purpose of this report is to provide long-term follow-up of 38 patients diagnosed of post-transplant lymphoproliferative disease (PTLD) included in a phase 2 clinical trial of first line therapy with rituximab and to evaluate the same therapy in a real world cohort of 21 consecutive patients treated once the trial was closed. Eligible patients were ≥ 18 years of age with a biopsy-proven CD20 positive B cell PTLD and treatment naive except for reduction of immunosuppression. Treatment consisted in four weekly infusions of rituximab at the standard dose of 375 mg/m². Patients in complete remission (CR) were followed without further treatment, and those in partial remission (PR) were treated with another four cycles of weekly rituximab. Median follow-up in the clinical trial was 13.0 years. Disease-specific survival (DSS) at 10 years was 64.7% [95% confidence interval (CI) 48.2–81.2%]. For those patients who achieved CR (61%), DSS at 5 and 10 years was 94.4% (95% CI 83.8–100%) and 88.1% (95% CI 72.6–100%), respectively, and only 1 patient progressed beyond 5 years. The median follow-up of the real world patients was 6.5 years. DSS at 5 years was 75.2% (95% CI 56.4–94.0%). DSS at 5 years of patients who achieved CR (38%) was 87.5% (95% CI 64.6–100%). In conclusion, PTLD patients in CR after rituximab have an excellent long-term outcome. These results not only apply in the clinical trial setting but are also reproducible in the real world. However, those patients who do not respond represent an unmet clinical need and should be included in prospective clinical trials.