Immunotherapy, cancer and PET

The treatment of cancer by immunotherapy has been a revolution, as it is the first strategy that manages to control the disease for prolonged periods of time. Its efficacy is associated with different imaging response patterns and the appearance of new toxicities. We would highlight two patterns of tumour response: pseudoprogression, or growth of tumour lesions after the start of immunotherapy treatment, followed by a significant reduction in lesions, and hyperprogression, acceleration of tumour progression and metastasis early after the start of treatment. The emergence of such patterns has generated new metabolic response criteria, such as PECRIT, PERCIMT, imPERCIST and IPERCIST. Of particular interest are the new immunoPET-specific biomarkers, as they allow the identification of patients presenting the tumour target and are useful for predicting response to immunotherapy.