Abstract
Combination therapy of lenvatinib, a multitargeted tyrosine kinase inhibitor (TKI), plus pembrolizumab, a monoclonal antibody targeting programmed death receptor 1 (PD-1), was recently approved by the Food and Drug Administration for therapy of advanced endometrial cancer. This case series highlights three patients with endometrial serous carcinoma who experienced disease stabilization or slow progression on lenvatinib plus pembrolizumab followed by rapid symptomatic growth of disease after lenvatinib discontinuation, and subsequent repeated response and symptom resolution after lenvatinib re-initiation. All patients died of disease complications 3 to 10 months after retreatment with lenvatinib. These observations highlight an important phenomenon of lenvatinib withdrawal rebound, likely driven by oncogenic signaling pathways upregulated in response to lenvatinib therapy. The findings of this case series represent a potential area for further research into the underlying mechanism for rebound and repeated response to lenvatinib, as well as strategies to mitigate disease flare related to lenvatinib withdrawal.