Abstract Introduction. Taxanes and platinums are first line treatment of breast cancer for early stages and metastatic disease and constitute the most commonly implicated chemotherapeutics in hypersensitivity reactions.1 Clinical manifestations range from mild skin reactions to anaphylaxis.2 Hypersensitivity reactions (HSR) to paclitaxel and carboplatin occur in a significant percentage of patients, with estimates of 30% and 40% respectively,3,4,5 leading to discontinuation of treatment.6 Using alternative drugs can be poorly tolerated or much less effective, entailing to high morbidity and mortality.7 Desensitization is the procedure performed to achieve a tolerance to the drug to which a HSR previously occurred, in order to maintain first-line treatment.8 The evaluation of the oncological response remains in the importance of assessing the shrinkage of the tumor and the time of progression of the disease.9 Objective: To describe the hypersensitivity reactions to paclitaxel and carboplatin, and the safety and effectiveness of desensitization protocols after anaphylaxis in patients with breast cancer. Materials and Methods: Original, retrospective, descriptive, and analytical study, approved by the Bioethics and Research Committee ON23-00016 code, included patients >18 years with breast cancer who developed a hypersensitivity reaction to first-line chemotherapy and performed a 3-bag-12-step desensitization according to the Brigham and Women's Hospital, Dana Farber Institute, Boston protocol. Results: Forty-five desensitization to paclitaxel or carboplatin were performed in 8 women with breast cancer, mean age 38.6 years. 6 patients developed HSR to paclitaxel, 83% of which were in the first application, and 2 patients developed HSR to carboplatin after several cycles. The most predominant symptom of HSR was cutaneous in 87% of the cases, and all patients presented cardiovascular HSR to paclitaxel. No patients developed HSR during desensitization. Currently, only 1 patient developed disease progression, while the rest presented a complete response to treatment. Discussion. HSR to paclitaxel appear in the 1-2 cycle,10 while to platinums after various exposures ( >6 cycles) similar to our study.3,4 The symptoms associated with paclitaxel are cardiovascular10,11 while urticaria is the most frequent in carboplatin.3,11 The desensitization protocol implemented did not develop HSR in any of the patients. Neoadjuvant chemotherapy in breast cancer has been shown to yield better disease-free interval results alongside improved pathological response.12 Conclusions. The program implemented in our hospital's chemotherapy desensitization clinic, replicating the model of the Dana-Farber Cancer Institute, Brigham, and Women's Hospital in Boston, has enabled cancer patients to continue with first-line treatment, thus improving their prognosis and quality of life, opening new areas of opportunity in the multidisciplinary management of these patients to improve overall survival. Characteristics of patients with hypersensitivity reactions HSR: hypersensitivity reactions ND: No data m: months yrs.: years Desensitization protocol to Paclitaxel IV (300 mg) IV: intravenous mg: milligram mL: milliliter h: hour Citation Format: Rosalaura V. Villarreal-González, Oscar Vidal-Gutiérrez, Javier A. Martínez-Moyano, Marianela Madrazo-Morales, Kathia S. Sáenz-Cantú, Patricia Rodríguez-Niño. Hypersensitivity reactions to paclitaxel and carboplatin in breast cancer: safety and effectiveness of desensitization [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-12-08.