A Trial of Radiotherapy and Durvalumab in DLBCL and FL

The primary objective for this study is to determine the safety profile of radiotherapy and durvalumab, a PD-L1 inhibitor. Primary endpoint: Toxicity, drug pharmacokinetics (PK), maximum tolerated dose (MTD) and recommended phase two dose (RPTD) of simultaneous radiotherapy plus durvalumab in patients with relapsed or refractory DLBCL or FL. Secondary endpoints: * ORR * Progression-free survival * Overall survival Exploratory endpoints include description of biological effects of combination radiotherapy plus durvalumab (Imaging results, immune function, PK and PD-see 'research methodologies') and in the PET-Sub-Study, biodistribution of 89Zr Durvalumab and 89Zr-IAB22M2C.