One of the main objectives when assessing patients who react to antineoplastics must be to ensure that they receive the required treatments without delay. From January to July 2021, at the Allergy Department at the Provincial University Consortium Hospital a pilot study was performed in which those patients suspected of having suffered a type I hypersensitivity reaction (grade 1 or 2) following Brown's anaphylaxis severity grading to a platin agent at the Provincial University Consortium oncology day unit, and once the reaction was properly treated and completely resolved, were subjected to a new procedure named as Same-Day Desensitization, which consists in the reintroduction and administration of full chemotherapy dose by allergists on the same day of the reaction by following the 1 bag/10 step protocol, looking forwards to systematize same-day reexposure using Same-Day Desensitization, doing it in the safest way possible. In total, 9 oncological patients suspected of having suffered a type I hypersensitivity reaction (grade 1 or 2) to a platin agent received total dose administration the same day of the initial reaction by following Same-Day Desensitization 1 bag/10 step protocol, without presenting further reactions. The manuscript describes a new approach in the use of Rapid Drug Desensitizations in reactive oncologic patients in treatment with platin agents, presenting the first 9 cases of oncologic patients who have been submitted to this procedure.

BackgroundIfosfamide is an antineoplastic agent with alkylating activity usually administered in combination with mesna. The latter is a thiol agent with uroprotective activity that prevents side effects such as haemorrhagic cystitis or nephrotoxicity which allows the administration of higher doses of ifosfamide without unwanted secondary effects. This combined treatment can be used for a wide range of tumours such as testicular, lung, lymphoma, and in advanced solid, soft-tissue sarcomas and gynaecological tumours. Ifosfamide-mesna is administered as a continuous infusion rather than in a bolus to avoid central nervous system toxicity.Case presentation A 47-year-old man with the diagnosis of stage IV renal sarcoma who received treatment with ifosfamide-mesna every 3 weeks in a consecutive 4-day infusion protocol. However, during the second chemotherapy cycle he presented urticarial lesions. In the absence of scientific evidence for risk of immediate reactions with this association, and given the lack of described experiences of allergic reactions with this chemotherapy combination, the aggressiveness of the tumour process, and the absence of validated skin tests, we proposed the completion of a 12-step desensitisation protocol.Conclusion The 12-step desensitisation protocol was well tolerated. Therefore, it is an appropriate and safe option in the case of suspected allergy to ifosfamide plus mesna. Keywords Ifosfamide plus mesna, desensitization, chemotherapy