Table 6.

Potential predictors to ICIs therapy in solid tumors and subdivided into different categories—starting from widely accessible to more specific ones.

Potential Predictors	Assessment	Difficult Access to Parameter Evaluation (Based on Patient Compliance, Cost, Availability)
Clinical features, including belonging to special populations (such as elderly, immunocompromised patients, organ transplant recipients, individuals suffering from autoimmune conditions)	Clinical	/
Serum markers	Blood-based	+
PD-L1 (and PD-1) expression	Histopathological, blood-based, molecular biology techniques	+/++
Tumor infiltrating lymphocytes	Histopathological, molecular biology techniques	+/++
Genetic alterations (tumor mutational burden and copy-number alterations)	Molecular biology techniques	++