Mature Results of a Prospective Trial of Rituximab in Patients (Pt) with Post Transplant Lymphoproliferative Disorder (PTLD) Unresponsive or Ineligible for Reduced Immunosuppression (RIS).

Background: PTLDs are typically B-cell neoplasms occurring as uncommon but serious complications of reduced T-cell immune surveillance associated with organ transplantation. RIS benefits only a subset of PTLD patients and cytotoxic therapy may be poorly tolerated. Therefore, in October 1998 we initiated a prospective study of rituximab in patients who failed or were unable to receive RIS and now report mature results.

Methods: Patients with CD20+ PTLD were eligible if they had failed to completely respond to RIS or RIS was contraindicated and had Karnofsky performance status >60, age 3–70 years (y), measurable disease, and no change in immunosuppression for at least 2 weeks and no cytotoxic therapy within 4 weeks. Rituximab was given as 375 mg/m2 weekly x 4 with disease evaluation at 1, 3, 6, 9, 12 and 18 months. Response data, survival curves, and the impact of clinical and pathological factors were evaluated.

Results: 24 of 26 enrolled pt were eligible and evaluable. Median age was 42y with 5 <17 y, 18 were male, and 14 progressed on RIS. Median time to PTLD from transplant was 47 months (m) (8 <24 m). 17/22 were EBV+, 17 were large cell or Burkitt histology, and 10 PTLD occurred in the allograft site. Response rate was 63% (46 %CR, 17% PR) and CRs were durable (1/11 progressed). With median follow-up of 65 m (range 44–82), outcomes at 5 y are: overall survival 48%, freedom from progression 41% and failure-free survival 21%. 7 pt died without progression, yielding 5 y cause-specific survival of 69%. Nine of 13 pt with disease progression were successfully salvaged with second-line therapy. In univariate analysis PTLD characteristics did not significantly correlate with outcome but 2/2 Burkitt pt quickly progressed.

Conclusions: Rituximab provided effective, durable treatment for ~40% of pt failing RIS in this series of mainly late PTLD and a majority of pt progressing after rituximab could be treated successfully. However, overall and failure-free survival reflect significant co-morbidity in this population.