Intracranial Response to Selpercatinib After Pralsetinib-Induced Disease Progression in Rearranged During Transfection Fusion-Positive Non-Small-Cell Lung Cancer: Case Report.

RET fusion-positive NSCLC accounts for 1% to 2% of lung carcinoma cases. Although two Food and Drug Administration-approved selective RET inhibitors, pralsetinib, and selpercatinib, have revealed efficacy in managing RET fusion-positive NSCLC, this case series is unique in its focus on the intracranial response to selpercatinib after disease progression during pralsetinib treatment. This report contributes to the literature by providing evidence of selpercatinib's potential as a treatment option in such refractory cases. The patients described in both cases were diagnosed with metastatic RET fusion-positive NSCLC and developed intracranial metastases during pralsetinib treatment. After switching to selpercatinib, both exhibited significant intracranial responses. The first patient reported a reduction in brain metastasis size and maintained a response for over 1.5 years. The second patient also responded intracranially to selpercatinib but unfortunately passed away 8 months later owing to pulmonary hemorrhage, possibly linked to prior radiation treatment. These cases highlight the potential efficacy of selpercatinib in treating intracranial metastases in RET fusion-positive patients with NSCLC after pralsetinib-refractory progression. The key takeaway is that selpercatinib may offer a viable treatment option in such scenarios, although more extensive studies are needed to determine its role as a monotherapy or in combination with other treatments.