Monotherapy rapamycin in renal transplant recipients with lymphoma successfully treated with rituximab

Posttransplantation B-lymphoproliferative (PTBL) disease is a severe complication of organ transplantation, which requires reduction of immunosuppressive treatment. The use of the anti-CD20 monoclonal antibody, Rituximab, improves the survival of these patients. In this setting, maintenance immunosuppressive therapy may represent a challenge. The mammalian target of rapamycin (m-TOR) inhibitor Rapamycin has antiproliferative effects that makes it a safe, efficient option to avoid graft rejection and reduce the malignancy risk. We studied 6 renal recipients (4 men and 2 women) of overall mean age of 50.66 +/- 15.89 years who were diagnosed with lymphoma at a mean time of graft function of 137.0 +/- 68.00 months. All of the patients were Epstein-Barr-negative. Four received a combination of Rituximab and cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP), and 2 received Rituximab only. In all cases complete remission persisted during follow-up of 21.83 +/- 8.34 months. The immunosuppressive treatment was switched to the m-TOR inhibitor Rapamycin at therapeutic trough blood levels of 5-8 ng/dL. The mean time of Rapamycin treatment was 15.5 +/- 8.96 months. Notably, we observed neither acute rejection nor relapse episodes. Renal function remained stable with no significant proteinuria. The serum creatinine level before switching to Rapamycin was 1.06 +/- 0.16 mg/dL and 0.9 +/- 0.14 mg/dL 12 months later. However, 1 patient had to stop Rapamycin treatment due to pneumonitis. Our study suggests that immunosuppressant monotherapy with Rapamycin is safe and efficient for renal recipients who develop lymphoma because of its antitumor effects without nephrotoxicity.