Successful desensitization in a patient with metastatic colorectal cancer presenting with regorafenib-mediated fix drug eruption

Introduction: Regorafenib is an oral protein kinase inhinitor approved fot the treatment of metastatic colorecral cancer. We present a first successful case of desensitization in regorafenib-related fix-drug eruption in the literature. Case report: A 44-year-old female patient was diagnosed with metastatic colorectal adenocarcinoma. The patient received regorafenib treatment for malignancy recurrence. The patient was admitted to adult allergy clinic with developing recurrent fix drug eruption in the second cycle, on the 10th day of regorafenib treatment. The patient was given the third cycle of regorafenib treatment with a 6-day desensitization protocol, the first day of which consisted of 6 steps and and the third cycle was successfully completed. Management and outcome: Regorafenib-mediated delayed hypersensitivity reactions occur less frequently and and regorafenib hypersensitivity reactions are difficult to manage and experience is limited. This is the first successful desensitization protocol developed by us for regorafenib-related fix drug eruption and more cases are needed to be reported to confirm the desensitization protocol. Discussion: There is only one successful regorafenib desensitization protocol for severe delayed hypersensivity reaction in the literature, but there is no protocol developed for mild type delayed hypersensivity reaction. The management of fix-drug eruption primarily involves discontinuation and avoidance of the offending drug but our patient had a mild delayed-type reaction and there was no alternative to regarofenib treatment. We developed the rapid 6-step desensitization protocol (Day 1). According to this protocol, the patient was able to continue regorafenib treatment successfully.