While cancer immunotherapy can produce dramatic responses, only a minority of patients respond to treatment (<30%). Reliable response biomarkers are needed to identify responders, and conventional imaging modalities have not proved adequate.

Some of the current methods used to predict immunotherapy response are monitoring CD8+ and CD3+ T-cell infiltration and PD-1/PD-L1 expression using biopsy. Because of the potential limitations of biopsy, alternative imaging approaches are established. focusing on total tumor rather than active immune

infiltrate hinders the successful correlation of these biomarkers with therapeutic efficacy. That’s why there is a need for a sensitive and specific biomarker. Granzyme B is a serine-protease released by CD8+ T cells and natural killer cells during the cellular immune response and represents one of the two dominant mechanisms by which T cells mediate cancer cell death .The scientists designed a PET imaging agent capable of detecting the release of this enzyme by actively engaged immune cells. Such an imaging agent would allow for repeated

Using this non-invasive method (Granzyme B PET) to predict immunotherapy response could provide a more personalized approach to immunotherapy, so that patients and oncologists can have more information about response at earlier time points, allowing for more options to be explored in the case of immunotherapy failure.