Hyperprogressive Disease and Early Hypereosinophilia After Anti-PD-1 Treatment: A Case Report.

Hyperprogressive disease (HPD) has been recently proposed as a new pattern of progression in patients treated with immune checkpoint inhibitors (ICIs). Until now, no biological marker has been found to predict this accelerated tumour growth. We describe the case of a 62-year-old women who experienced a marked increase in absolute eosinophil count (AEC) concurrently with a huge radiological progression after the first nivolumab dose in absence of other immune-related adverse events (irAEs). Further investigations are needed to establish the role of early hypereosinophilia as a marker of progression and to identify patients who might not benefit from ICI treatment.