In the era of immuno-oncology, programmed cell death 1 (PD-1) and programmed cell death ligand 1 (PD-L1) inhibitors have demonstrated a clear survival benefit as a single agent or in combination compared with standard chemotherapy in both treatment-naive patients
1-4 and patients previously treated
5-8 for advanced non–small cell lung cancer (NSCLC). However, progression rates reported with single-agent PD-1/PD-L1 inhibitors are in some cases equal to or higher than with conventional treatment, ranging from 33% to 44% in pretreated patients with NSCLC.
5-7 Recently, an acceleration of tumor growth during immunotherapy, defined as hyperprogressive disease (HPD), was reported in 9% of advanced cancers
9 and in 29% of patients with head and neck cancer
10 treated with PD-1/PD-L1 inhibitors.