Pre-Emptive Rituximab for Epstein-Barr Virus Reactivation Post Stem Cell Transplant: High CRP and PTLD At Initiation of Treatment Confer Inferior Outcome

Background: Epstein-Barr virus (EBV) associated post-transplant lymphoproliferative disease (PTLD) is an important complication of allogeneic stem cell transplantation (alloSCT). Quantitative PCR monitoring of EBV genomes in blood and pre-emptive administration of Rituximab in patients with high viral load is emerging as a strategy to reduce mortality from PTLD. However, factors predicting for response in this patient population are not well understood. Aim: To report the frequency and characteristics of patients treated for EBV reactivation and to identify factors predicting outcome. Methods: This retrospective analysis examined all patients needing treatment with Rituximab for EBV reactivation after undergoing alloSCT at University Hospital Birmingham, UK between June 2009 and February 2011. A total of 92 T-deplete and 9 cord blood transplant patients were monitored weekly with quantitative EBV PCR testing of whole blood for a minimum of 6 months. Patients with EBV reactivation were given Rituximab pre-emptively when viral DNAemia exceeded 30, 000 copies/ml, whereas patients presenting with PTLD were treated irrespective of viral load. A maximum of 4 weekly doses of Rituximab 375mg/m2 were given until PCR negativity or resolution of symptoms. Cases of PTLD were either biopsy-proven or diagnosed as probable PTLD if viral DNAemia was associated with clinicoradiologic evidence of disease. Results: Of 101 patients undergoing alloSCT monitored by quantitative EBV PCR testing 24 (24%) were treated with Rituximab for EBV reactivation. The median age of treated patients was 58 years and 75% were male. Two patients received myeloablative and 22 received reduced intensity conditioning. Donor stem cells were sibling in 6, unrelated in 14 and cord blood in 4 patients. EBV DNAemia over 30, 000 copies/ml occurred in 23 of 24 treated patients. Of these, 14 had no evidence of PTLD whilst 9 of 23 had evidence of either probable (6 cases) or biopsy-proven (3 cases) PTLD at the time of initiating treatment. One patient was treated for biopsy-proven PTLD with a viral load that never exceeded 30, 000 copies/ml. The median interval from alloSCT to first PCR positivity was 99 days (IQR 70 – 146 days) and the median interval from first PCR positivity to exceeding the 30, 000 copies/ml threshold was only 7 days (IQR 0 – 14 days). Notably, treated patients with PTLD became PCR positive significantly earlier after alloSCT than those without PTLD (median 71 vs. 119 days; p=0.01*). Median viral loads at first PCR positivity, at the 30, 000 copies/ml threshold and at peak viral load were 1.1×104, 8.2×104 and 2.2×105 copies/ml respectively, of which peak viral load was significantly higher in patients with PTLD (median 1.1×106 vs. 1.4×105 copies/ml; p=0.01*). Patients reactivating EBV without PTLD received a median of 3 doses of Rituximab whilst patients with PTLD received a median of 4 doses. Complete response (defined by PCR negativity and clinioradiologic resolution of disease) was seen in 13/14 (93%) patients without PTLD versus 6/10 (60%) patients with PTLD. Notably, among patients who achieved PCR negativity the median interval from initiation of treatment to PCR negativity was significantly longer in those with PTLD (median 28 vs. 13 days; p=0.005*). All 4 patients with Rituximab-refractory PTLD died despite further treatment with chemotherapy in 3 cases. All-cause mortality for treated patients was 10/24 (42%). Regarding predictors of response to Rituximab, a diagnosis of PTLD at treatment initiation showed a clear tendency to significance (p=0.056**) whilst raised CRP >30 was highly significant (p=0.003**). Other variables including age, sex, conditioning, donor type, viral load, LDH and albumin were not significant. Conclusions: Focussing exclusively on alloSCT patients treated with Rituximab under a pre-emptive management strategy, this study demonstrates that patients who require treatment typically display an early and vigorous EBV DNAemia. Notably, among patients treated for EBV reactivation those with PTLD become EBV PCR positive earlier, have higher peak viral loads and take longer to reach PCR negativity after treatment. Rituximab responsiveness is a key determinant of outcome, as patients with refractory disease have poor survival irrespective of chemotherapy. Among patients who reactivate, those with PTLD or with raised CRP experience inferior outcomes. *Mann-Whitney U Test **Fisher's Exact Tes