Immuno-pet IMaging ResPonses AdministeRed Immune CheckpoiNt InhibiTor

6 mL of the study drug will be administered subcutaneous injection in the abdominal fat fold. If SC injections in the abdominal location are not possible, SC injections can be administered in a distributed manner in the thighs. SC injections in the upper extremities (eg, deltoid, upper and lower arm) are not permitted. Any observed abnormality at the injection site (e.g. erythema, induration, ecchymosis, injection site pain, injection site pruritus) will be monitored and judged by the investigator to determine whether a corresponding AE should be reported.

Patients will receive a total dose of 24Gy irradiation to the tumor, fractionated in 3 doses of 8Gy, on three consecutive days and starting on the day of first sasanlimab administration.

Prior to sasanlimab injection and prior to surgery, \[89Zr\]Zr-crefmirlimab berdoxam (1.5 mg protein dose labelled with activity dose 37 MBq Zirconium-89) will be administered via an intravenous catheter. After 21-27 hours after injection patient will undergo a whole-body PETscan te detect CD8+ T-cell infiltration.