INTRODUCTION: Urothelial carcinoma is the prevailing type of bladder cancer, characterized by expression of the programed death-ligand-1-protein (PD-L1). Avelumab is an anti-PD-L1 monoclonal antibody used in urothelial carcinoma. It is associated with an incidence of 47.4% and 25.2% in grade 3 adverse events or greater, respectively
gastrointestinal symptoms and cutaneous affections are the most common. CASE REPORT: A 52-year-old male with a history of rectal cancer and non-muscle-invasive bladder carcinoma. PET/CT revealed adenopathies in the pelvic region, the biopsy confirmed metastatic urothelial carcinoma. Next PET/CT indicated progression. Treatment with Cisplatin + Gemcitabine led to complete response after 4 cycles. Maintenance with Avelumab was indicated. Fifteen minutes after the first Avelumab administration, the patient experienced hypotension, presyncope, skin itching, and nasal congestion. Epinephrine, hydrocortisone, and physiological solution were administered, with resolution of symptoms. MANAGEMENT & OUTCOME: Since Avelumab is first-line maintenance therapy in this patient, a desensitization protocol was performed with (3-bag, 12-steps). The patient was premedicated with acetaminophen and chlorpheniramine. The protocol was successfully completed without hypersensitivity reactions for 6 cycles. DISCUSSION: Patients with hypersensitivity reactions to their first line of treatment are challenged to continue the best approach. We detail the case of a patient diagnosed with metastatic urothelial carcinoma who underwent a desensitization protocol for Avelumab after presenting a severe allergic reaction. The patient tolerated Avelumab throughout the protocol with no complications, achieving the total dosage for his maintenance therapy
drug desensitization is a safe and effective procedure in patients with hypersensitivity reactions to their first-line treatment.