Hyperprogression and pseudoprogression are two atypical responses to immune checkpoint inhibitor therapy that affect therapeutic decisions and prognosis. Identification of predictive biomarkers for atypical responses either before or during treatment remains a huge unmet need in cancer immunotherapy. Many studies have looked at potential biomarkers, including clinical factors and laboratory findings (e.g., peripheral blood counts, circulating tumor DNA, cytokine levels). The results of these studies have been inconsistent, possibly due to small sample sizes, different tumor types and heterogeneity of the definition of these atypical responses.