Leonie Voorwerk, MD, The Netherlands Cancer Institute, Amsterdam, The Netherlands. gives an update on the critical role of eosinophils during responses to immune checkpoint blockade in patients with breast cancer. Further validation was carried out in samples from metastatic non-small cell lung cancer (NSCLC), metastatic bladder cancer, metastatic mismatch repair deficient cancer (dMMR) or early stage dMMR and MMR-proficient colon cancer. The study showed that an increase in eosinophils was associated with responses in multiple tumor types. Further work in mouse models showed a function role for eosinophils during treatment. This interview was recorded via an online conference call with The Video Journal of Oncology (VJOncology).