Osimertinib tolerance in a patient with Stevens Johnson Syndrome during Osimertinib treatment followed by Pembrolizumab

Abstract Background: Osimertinib has emerged as an important tool in the treatment of non-small cell lung cancers (NSCLC) with certain activating mutations of epidermal growth factor receptor (EGFR). However, Osimertinib may cause adverse effects, including severe cutaneous adverse reactions (SCARs) such as Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). The risk of certain adverse effects may be increased in the setting of recent use of immune checkpoint inhibitor (ICI) therapy, although it is unclear whether recent use of ICI therapy is a risk factor for Osimertinib-induced SJS specifically. Case presentation: We present a patient with EGFR L858R mutation-positive metastatic NSCLC who developed Osimertinib-induced SJS after recent administration of eight cycles of a pembrolizumab-containing chemotherapy regimen. Osimertinib, which was the best treatment targeting his lung cancer, was avoided due to history of SJS. Four years later, because of unresponsiveness or side effects of alternative treatments, he underwent Osimertinib challenge and tolerated it. Conclusion: This case highlights the importance of multi-disciplinary care and supports the hypothesis that the risk of SJS to Osimertinib is significantly higher in the context of recent administration of ICI therapy and, patients may tolerate Osimertinib after certain time has elapsed after the last dose of ICI.