This trial is comparing whether using a drug called sirolimus for graft versus host disease
(GVHD) prevention can decrease the chance of the participant's lymphoma relapsing after
transplantation, compared to using a standard GVHD prevention regimen without sirolimus.
Since mTOR inhibitors have anti-lymphoma activity, their use after transplantation may lead
to a decreased risk of relapse and hence better transplantation outcome.