Anaphylactic shock in a small cell lung cancer patient receiving atezolizumab therapy: a rare but potentially fatal complication

Immunotherapy has been a revolutionary innovation in cancer therapy in recent years, but it is accompanied by various unique immune-related adverse events (irAEs). Among these irAEs, anaphylactic shock is very rare. Here, we report a case of a patient who developed anaphylactic shock after receiving one dose of atezolizumab. A 74-year-old male patient with small cell lung cancer experienced recurrence 10 years after surgery. After one cycle of treatment, the patient developed a grade 2 rash and recovered after receiving oral methylprednisolone tablets. In the second cycle, atezolizumab was discontinued. Then, the patient was scheduled to receive atezolizumab plus carboplatin and etoposide again after three weeks, but approximately three minutes after an intravenous infusion of atezolizumab, the patient developed signs and symptoms of anaphylactic shock, such as dyspnea, cold limbs, and loss of consciousness. At this point, the infusion was immediately stopped, and a normal saline infusion was administered. Meanwhile, ECG monitoring, supplemental humidified high-flow supplemental 100% oxygen, epinephrine, dopamine, hormone treatment with methylprednisolone, and other anti-shock treatments were carried out. For better recuperation, this patient was transferred to the intensive care unit for further treatment and was discharged two days later. Anaphylactic shock develops rapidly and is also a very severe complication. Prompt detection, diagnosis, and therapeutic intervention are the basics for survival.