Open Access

Background: mTOR-Is positively influence the occurrence and course of certain tumors after solid organ transplantation. mTOR-inhibitor (mTOR-I) treatment, either alone or in combination with Calcineurininhibitors (CNIs), significantly reduces the incidence of malignancies after organ transplantation. However, there is no information on which mTOR-I, Sirolimus (SIR) or Everolimus (ERL), has a stronger anti-tumoral effect. Methods: The current literature was searched for prospective randomized controlled trials in renal transplantation. There were 1.164 trials screened, of which 20 could be included (7465 patients). We performed a network meta-analysis to analyze the relative risk of different types of mTOR-I compared to CNI treatment on malignancies after transplantation. A minimum follow-up of 24 months was mandatory for inclusion. Results: Four different types of mTOR-I treatment were analyzed in network meta-analyses—SIR mono, ERL mono, SIR with CNI, and ERL with CNI. The average follow-up of all trials was 43.8 months. All four different mTOR-I regimes showed a significant reduced relative risk for malignancies compared to a regular CNI-treatment with the strongest effect under SIR in combination with a CNI (RR 0.23, CI 0.09–0.55, p = 0.001). This effect remained consistent for all tumor entities except non-melanoma skin cancer (RR 0.25, CI 0.07–0.90, p = 0.033). Conclusions: It is well known that an mTOR-I based treatment in transplant patients reduces the risk of tumor manifestation in comparison to CNI treatment. A combination of SIR and CNI seems to be the most potent mTOR-I therapy against malignancies.