Anti-Tumor Immunity in Solid-Organ Transplant Recipients

Solid-organ transplant (SOT) recipients have an increased risk of malignancies and poor oncological prognosis compared to the general population. A central reason for both is that various factors unique to transplantation coalesce to dampen anti-tumor immunity. These include graft or immunosuppressive therapy-related T-cell dysfunction, microenvironmental changes in grafts due to ischemic/reperfusion injuries peri-transplant and comorbidities such as metabolic syndrome. Both innate and adaptive immunity are heavily implicated in cytotoxicity effected by systemic therapeutic agents, not just immune checkpoint inhibitors (ICIs) but also conventional chemotherapy and targeted therapies. Hence, impaired anti-tumor immunity may also affect the treatment efficacy of these agents. Generally, clinical data for systemic therapies in transplant recipients is constrained to retrospective and heterogenous case reports and series only, with a low level of evidence and significant risk of bias. For ICIs, the efficacy in SOT recipients is relatively well preserved in cutaneous squamous cell carcinomas but seems diminished in other tumor types compared to non-transplant recipients. Data for other agents are limited, but the efficacies of chemotherapy in SOT recipients with colorectal cancer and sorafenib/lenvatinib in LT recipients with recurrent hepatocellular carcinoma seem preserved. Given the prevailing trend of broadening the use of transplantation in patients with cancer, further clinical and translational studies to develop strategies to enhance anti-tumor immunity while ensuring graft preservation are urgently needed.