Abstract
Introduction
Post-transplant lymphoproliferative disorders (PTLD) are mostly Epstein-Barr virus (EBV) positive lymphoid proliferations resulting from immunosuppression following allogeneic stem cell or solid organ transplantation (SOT). Despite this strong association, there is a lack of data evaluating the risk of PTLD in SOT patients (pts) with (w/) EBV viremia. The significance of EBV detection remains unclear and can lead to unwarranted preemptive treatments in SOT pts. The aim of this study is to assess the association between peripheral blood EBV viral load and risk of PTLD post SOT.
Methods
We identified 6468 adult and pediatric pts from the Cleveland Clinic SOT database who underwent SOT from 2002-2016. We included pts who had ≥1 EBV viral load test by PCR, and excluded pts w/ first EBV test at or after PTLD diagnosis. EBV viral load was quantified by polymerase chain reaction (PCR) of whole blood samples and expressed as log copies/mL. Lower detection limits varied from 2.00 to 2.70 log copies/mL. EBV monitoring post SOT was done at the physician's discretion. Potential risk factors for PTLD were assessed using Fine and Gray competing risk regression. Stepwise analysis was used to identify multivariable risk factors. Landmark analyses at 2 and 6 months post SOT (LM-2 and LM-6) were performed based on pts' peak pre-landmark EBV levels. Pts were excluded if they died, lost follow-up (f/u) or developed PTLD prior to the landmark. Two multivariable models were assessed at each landmark using EBV level cutoffs of 3.00 and 4.00 log.
Results
Of 6324 pts w/ available f/u data, 3348 (52%) had ≥1 quantitative EBV PCR test and were included in this analysis w/ a total of 91,067 tests performed. Median age at SOT was 54 years (range 0.3-79) and 63% were male. The most common SOT was kidney (38%) followed by lung (37%), liver (18%), heart (7%), pancreas (6%) and intestine (2%), w/ 7% receiving >1 organ type (Table 1). Of 3348 pts included, 1503 (45%) developed EBV viremia and 68 (2%) developed PTLD; 45/1503 (3.0%) and 23/1845 (1.2%) of pts w/ and without (w/o) EBV viremia, respectively. EBV was detected in 44% of pts w/o PTLD and 66% of pts w/ PTLD. Median age at PTLD diagnosis was 58 years (range 1-75), with a median time from SOT to PTLD of 33 months (range 2-146). PTLD morphology was DLBCL (n=39), polymorphic (n=9) Burkitt (n=5), other (n=10) and unknown (n=5). EBV-encoded RNA (EBER) testing in tumor was positive in 47%, negative in 44% and unknown in 9% of cases. In pts w/ and w/o PTLD, tacrolimus was the most common immunosuppressant used at 1 month (99% and 89%), 1 year (94% and 88%) and 2 years (81% and 74%) post SOT, respectively. First EBV was checked at a median of 54 days (range 0-5090) in pts w/o PTLD and 28 days (range 0-4308) in pts w/ PTLD. The median number of EBV tests/pt before PTLD or last f/u was 4 (range 1-214) in pts w/o PTLD and 6 (range 1-123) in pts w/ PTLD. Peak EBV levels ≥3.00 and ≥4.00 log were detected in 36% and 13% of pts w/o PTLD, and 60% and 40% of pts w/ PTLD, respectively. Median f/u in both cohorts for pts who were alive was 6.1 years. In multivariable analysis (MVA) for non-EBV risk factors for PTLD, liver (HR 2.19, 95% CI 1.31 - 3.66, p=.003) and intestine SOT (HR 4.62, 95% CI 1.84 - 11.6, p=.001) were the only factors associated w/ higher PTLD risk; age, years since SOT, gender, race, other types of SOT and >1 SOT were not significant. 1685 pts were eligible for LM-2 (43 w/ PTLD) and 2093 for LM-6 (36 w/ PTLD). In univariable analysis at LM-2 and LM-6, peak EBV levels ≥4.00 log (LM-2: HR 2.72, p=.016; LM-6: HR 7.08, p<.001) and ≥5.00 log (LM-2: HR 8.64, p=.006; LM-6: HR 7.06, p=.002) were associated w/ increased risk for PTLD (Table 2 and Figure). Additionally, at LM-6, peak EBV level ≥3 was predictive for PTLD development (HR 2.18, p=.018). MVA at LM-2 was significant using cutoff ≥4 log (HR 2.90, p=.011), and at LM-6 using ≥3 (HR 2.21, p=.02) and ≥4 log (HR 6.91, p<.001). The cumulative incidence rate (CIR) for PTLD was 2.4% at 6 months and 4.9% at 1 and 2 years post SOT in pts w/ EBV ≥4 log by LM-2. By LM-6, EBV value of ≥4 log resulted in a CIR of 3.7% and 5.7% at 1 and 2 years, respectively.
Conclusion
In this large cohort of SOT pts, <50% had EBV viremia post SOT with only 3% of pts with EBV viremia developing PTLD. EBV viral load of ≥4 log copies/mL at 2 and 6 months was associated with increased risk of PTLD. EBV monitoring post-transplant may benefit a subset of pts, and prospective studies are warranted to evaluate if preemptive treatment can reduce PTLD risk in high-risk pts.
Hill:Pharmacyclics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Genentech: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding; Pharmacyclics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees.
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