Kaplan-Meier EFS estimates. EFS estimates stratified by serum EBV DNA status (≤60 copies per 100 µL serum compared with >60 copies per 100 µL serum) at (A) baseline and (B) day 8. Note that there were patients with serum EBV copy number determinations but no ISH, so the number of patients included is greater than that shown in Table 1.