Prospecitve Quantitative PCR Monitoring of Allogeneic Stem Cell Transplant (SCT) Patients at High Risk for EBV Associated PTLD.

Background: EBV associated PTLD is a severe complication after allogeneic SCT with high mortality. Several studies have reported identified risk factors for development of PTLD such as an EBV serological mismatch between donor and recipient, and the use of T-cell depleted or mis-matched stem cell grafts including cord blood grafts. Detection of high EBV viral load in blood specimens has also been associated to the development of PTLD. Treatment with rituximab at the time of EBV viremia has been suggested as a way of reducing the risk for PTLD.

Methods: A strategy for prospective monitoring was introduced 050701 in “high risk” patients while the “standard risk” patients were to be sampled only based on clinical suspicion. Patients were to be monitored at least weekly if they had a diagnosis of lymphoma, there was a serological mismatch for EBV between donor and recipient, a recent primary EBV infection before SCT; or were to be transplanted with a cord blood graft. 124 patients transplanted between 050701 and 070515 were included; 41 patients were classified as “high risk” while 83 were “standard risk”. High risk features were: EBV serological mismatch n= 21, cord blood grafts n=15, lymphoma n=10, primary EBV infection n=1 (patients could have more than one high risk feature). The EBV viral load was determined by a TaqMan PCR technique using the EBV BNRF gene. EBV DNA was extracted from serum with MagNa Pure LC. Rituximab were to be given if a patient developed a viral load of 10000 copies/ml or had symptoms suggestive of EBV associated disease.

Results: A total of 746 blood samples were analyzed for EBV DNAemia; a median of 6 samples in the “high risk” and 2 samples in the “standard risk” group (p=0.03). 14/41 (34%) patients in the “high risk” group compared to 11/83 (13%; p=.009) in the “standard risk” group had EBV detected at least once. In patients experiencing EBV infection, the median viral was 5500 copies/ml (225-1.4 x10⁶) load in the “high risk” group compared to 225 (225-2.3 x10⁶ in the “standard risk” group (p=.10). Eight patients (19%) in the “high risk” group and 3 (3.6%) in the “standard risk” group received rituximab (p=.006). Three patients (7.3%) in the “high risk” and one (1.2%) in the “standard risk” group (p=.10) developed PTLD giving a total frequency of 3.2%. One patient died from PTLD in each group (ns). Thus, the mortality in EBV associated PTLD was 2/124 (1.6%) in the entire group, 2.4% in the “high risk”, and 1.2% in the “standard risk” group.

Conclusions: EBV viral load monitoring directed to SCT patients at “high risk” for EBV associated PTLD resulted in a higher number of detected EBV DNAemias and more patients receiving preemptive rituximab therapy while the risks for PTLD and PTLD associated mortality were no higher than in “standard risk” patients.