A systematic review on the emerging association between the occurrence of immune-related adverse events and clinical outcomes with checkpoint inhibitors in advanced cancer patients

The correlation between clinical outcomes and treatment-related adverse events (AEs) has always been a debated topic in clinical oncology. Despite toxicities pharmacodynamics effects, the misunderstanding has always been around the corner: AEs themselves could lead to morbidity and mortality; on the other hand, the choice of the clinical outcomes to measure is not univocal. After the advent of immune checkpoint inhibitors (ICIs), such as anti-cytotoxic T-lymphocyte-associated protein 4 and anti-programmed death-1/programmed death ligand-1, new class-specific AEs have emerged, called immune-related AEs (irAEs). With irAEs, the correlation between toxicity and clinical outcomes has suddenly been suggested, but it is still to be proven. We conducted a systematic literature review regarding this emerging association, pointing out all the available data and speculating on the possible underlying mechanisms. Thirty-six studies were included in the analysis, involving different malignancies (mostly melanoma and lung cancer), with different measured clinical outcomes. The most of them were retrospective. Despite the high heterogeneity, and the enormous biases of the revised studies, we can assume that irAEs occurrence is linked to the therapeutic activity of immune checkpoint inhibitors, with a (certain) direct proportionality, maybe subtending the likelihood of an immunogenic phenotype. This phenomenon seems to occur with both anti-cytotoxic T-lymphocyte-associated protein 4 and anti-programmed death-1/programmed death ligand-1, and across different solid malignancies.