Nocebo Effect During Letrozole Desensitization: A Case Report.

This report describes the case of a 46-year-old woman with breast cancer and a history of multiple drug hypersensitivity reactions, who developed atypical allergic-like symptoms with three different adjuvant endocrine therapy regimens. As the use of an aromatase inhibitor was considered essential for her treatment, a three-day desensitization protocol to letrozole was implemented. During the protocol, she developed pruritic erythema following placebo administration. Despite this, the protocol was completed, with only mild side effects (oropharyngeal pruritus and headache), which were managed symptomatically. A diagnosis of nocebo reaction was disclosed to the patient after the desensitization process. She continued daily treatment with 2.5 mg of letrozole without further hypersensitivity complications.