Interim Analysis Of The Largest Prospective Trial To Date In Adult Cd20-Positive Post-Transplant Lymphoproliferative Disorder (Ptld): Introducing Risk-Stratified Sequential Treatment (Rsst).

8030 Background: The prospective, multicenter international phase II PTLD-1 trial of sequential treatment (ST, 4 cycles of weekly rituximab followed by 4 cycles of CHOP-21 + G-CSF) in adult CD20-positive PTLD demonstrated excellent efficacy (90% overall response rate, ORR) and safety (11% treatment-related mortality, TRM). As the response to rituximab predicted overall survival (OS), the trial was amended in 2007 introducing risk-stratified sequential treatment (RSST) according to the response to rituximab (NCT00590447). Methods: Following rituximab on days 1, 8, 15 and 22, RSST consisted of 4 3-weekly courses of rituximab monotherapy for patients (pts) in complete remission (CR, low risk) while all others (high risk) received 4 cycles of R-CHOP-21 + G-CSF. Key exclusion criteria were CNS involvement, HIV infection, severe organ dysfunction not related to PTLD, and ECOG > 2. Primary endpoint was ORR. This is an analysis of the first 91 patients treated with RSST. Results: 79/91 pts had monomorphic, 12 polymorphic PTLD. 41/91 pts were kidney, 27 liver, 12 heart, 7 lung or heart+lung, 3 heart+kidney and 1 kidney+pancreas transplant recipients. Median age at diagnosis was 60 years (range 20-82). 73/91 pts had late PTLD and 39/85 PTLDs were EBV-associated. 1 pt died before initiation of treatment; 5 pts discontinued treatment after 4 cycles rituximab. TRM of RSST was 7/90 (8%) including 5 deaths with unknown remission status. ORR was thus 74/80 (93%, 95%CI: 84-97%; CR: 62/80 [78%]). 24/90 pts (27%) achieved CR with 4 cycles of rituximab. After a median follow up of >3 years, relapse rate in low risk pts was not increased by rituximab consolidation in RSST compared to CHOP consolidation in ST (3/23 vs. 5/14, p=0.104]). In patients in PD after rituximab, R-CHOP was more effective than CHOP in achieving CR (15/23 vs. 3/11, p=0.038). OS at 3 years was higher with RSST (70%, 95% CI: 60-82%) compared to ST (61%, 95%CI 49-72%) but this difference was not significant. Conclusions: With RSST 27% of pts were classified as low risk and achieved durable tumor control without chemotherapy while R-CHOP seems more efficient than CHOP in in high risk patients.