Objectives: Assessing the safety and efficacy of immune checkpoint inhibition in risky cancer patient subgroups: pre-existing organ failure, elderly, presence of auto-immune disease, transplanted patients and brain metastasis treated with immune checkpoint inhibitors. Methods: PubMed, Web of Science and Google scholar databases were searched for English articles published prior to February 2019. Search terms used were organ failure, dialysis, elderly, organ transplant, liver disease, auto-immune disease, immunosuppression, and brain metastasis. Results: Our literature data indicate that immune checkpoint inhibition in the majority of these subpopulations can be administered safely without any loss of efficacy. These data are mostly based on case-reports as only a minority of high-risk patients were included in (the earliest) clinical trials. Validation of these results is necessary on a larger scale. Conclusion: Future trials should not automatically exclude aforementioned patient groups but alter the study design and make their inclusion possible, since more data are needed to answer several remaining questions in these populations. Especially since ICI appears to be safe to administer in these patients.