The role of immune checkpoint blockade for treatment of thymic epithelial tumors—a delicate balance between efficacy and side effects
Therapeutic options for patients with unresectable or metastatic thymic epithelial tumors (TETs) are limited. There is no approved treatment for patients with advanced TETs whose disease has progressed after first-line platinum-based chemotherapy. Immune checkpoint inhibitors (ICIs) that target the programmed cell death-1 (PD-1)/programmed death ligand-1 (PD-L1) pathway have been shown to be effective in a number of tumor types and have gained approval for multiple indications. Emerging evidence from clinical trials suggests that immune checkpoint blockade may be a viable therapeutic option for patients with TETs. Anti-PD-1/PD-L1 antibodies are active in a fraction of patients with advanced TETs with objective response rates (ORRs) ranging between 20–25%. As observed in other tumor types, responses to anti-PD-1/PD-L1 therapy tend to be durable in TETs. The incidence of serious immune-related adverse events (irAEs) however is higher in TETs than in other tumor types, necessitating vigilant monitoring of adverse events (AEs). Future studies of ICIs in patients with TETs should focus on developing more effective immunotherapy strategies, defining subsets of patients who are likely to benefit from immune checkpoint therapy, and potentially identifying patients at higher risk of autoimmune toxicity.