Critical complications in cancer patients admitted to the ICU in the era of immunotherapy: recognition, differential diagnosis, and management.

Background: Immunotherapy has introduced a new spectrum of ICU-relevant complications in patients with cancer, including hyperinflammatory syndromes, neurotoxicity, severe pneumonitis, myocarditis, and overlapping infectious complications. Objective: To review the major life-threatening complications of cancer immunotherapy from an ICU perspective, focusing on recognition, differential diagnosis, and management. Content: We discuss the critical illness patterns associated with CAR-T therapy, immune checkpoint inhibitors, and bispecific T-cell engagers using a syndrome-based framework. Key topics include cytokine release syndrome and HLH/MAS, immune effector cell-associated neurotoxicity syndrome, respiratory failure related to pneumonitis and infection, cardiovascular emergencies such as myocarditis and arrhythmias, and other less common but ICU-relevant organ toxicities. We also summarize the major diagnostic conflicts in the ICU and propose general principles for organ support, immunomodulatory therapy, infection management, and multidisciplinary care. Conclusion: Immunotherapy-related critical illness is increasingly relevant in modern oncologic intensive care. Because these syndromes are often clinically overlapping yet potentially reversible, optimal management requires early ICU escalation, parallel diagnostic reasoning, and integrated supportive and syndrome-directed treatment.