Two instances of successful oral desensitisation following hypersensitivity reaction in a patient receiving osimertinib: a case report

Background

Osimertinib is an irreversible epidermal growth factor receptor (EGFR) tyrosine-kinase inhibitor (TKI) and an available therapy for patients with non-small cell lung cancer (NSCLC) that have an EGFR or T790M mutation. It has become the preferred TKI in this patient group as it is superior to first-generation TKIs; however, osimertinib may be discontinued due to various toxicities or reactions.

Aim

We report two instances of successful osimertinib desensitisation in a 70-year-old woman requiring treatment for NSCLC following two hypersensitivity reactions presenting as angioedema and urticaria.

Clinical details

Osimertinib desensitisation started at 5 mg/day and was gradually increased to 80 mg/day over a period of 30 days.

Outcomes

The patient continued osimertinib 80 mg daily for over a year until treatment was withheld for 4 weeks due to thrombocytopenia and diverticulitis. She restarted osimertinib, completing a second desensitisation to a reduced dose of 40 mg daily without serious adverse effect. The patient continues reduced-dose osimertinib with stable disease.

Conclusion

This case report proposes an osimertinib desensitisation strategy useful for select patients experiencing osimertinib-induced hypersensitivity reactions. It also demonstrates that if there is prolonged disruption to treatment, a second desensitisation can be completed successfully in the same patient so effective treatment in NSCLC may be continued.