Antibody–Drug Conjugates Plus Immune Checkpoint Inhibitors for Sustained Disease Control in Advanced Solid Tumors

Antibody–drug conjugates (ADCs) combined with immune checkpoint inhibitors (ICIs) improve outcomes in selected advanced solid tumors, but clinical benefit does not establish pharmacological synergy. This narrative review evaluates disease control during ADC–ICI therapy and the implications for radiotherapy in recurrent or metastatic disease. Prolonged disease control is assessed primarily through progression-free survival in randomized trials; response duration provides complementary evidence among responders. Overall survival, quality of life, and toxicity determine the broader clinical value of treatment. Randomized trials support specific regimens in urothelial, breast, and lung cancers, whereas negative studies argue against generalization across drugs and diseases. Antigen expression, payload delivery, and the immune microenvironment may contribute to heterogeneous outcomes, but their clinical roles remain incompletely established. Reported treatment durations do not define optimal stopping times. Radiotherapy can address local symptoms, but whether it improves systemic disease control during ADC–ICI therapy remains unproven. We distinguish direct three-modality evidence from indirect ADC–radiotherapy and ICI–radiotherapy studies and identify priorities for patient selection, outcome assessment, and safety monitoring. Current evidence supports regimen-specific treatment selection and toxicity-directed modification, not routine radiotherapy addition or elective drug withdrawal across disease settings.