Sarah Verhoeff

87 [89Zr]Zr-DFO-durvalumab PET/CT before durvalumab treatment in R/M SCCHN patients RESULTS Baseline characteristics Between April 2019 and December 2020, 37 patients were screened, three were considered ineligible and one declined to participate. [89Zr]Zr-DFO-durvalumab PET dose finding was performed in 14 patients (Supplementary Figure S1). 21/33 (64%) patients presented with metastatic disease, most frequently located in lung (45%) and lymph nodes (39%). PD-L1 CPS scores could be determined in 27 patients (82%), including 17 patients with only archival tumor tissue available. Baseline characteristics are reported in Table 1. Durvalumab treatment In total, 31/33 patients started durvalumab treatment. Two patients showed rapid disease progression before treatment initiation and were offered best supportive care. One other patient showed rapid disease progression before first disease evaluation at 8 weeks. After a median followup of 12.6 months, the median time on durvalumab treatment was 5.3 months (range 1.2-26.5). The median PFS was 5.3 months (95%CI 2.96-7.62), and median OS was 13.1 months (95%CI 7.88-18.40). The survival rate at 12 and 24 months was 58% (95%CI 8.82-11.28) and 45% (95%CI: 8.91-24.87), respectively (Supplementary Figure S2). The ORR was 26%, including three patients with complete response and five patients with partial response. The best response to durvalumab treatment per patient is depicted in Figure 1. The DCR at 16 weeks was 48% with a mean response duration of 7.8 months (range 1.7-21.1). The most frequent reported grade 3-4 treatment-related adverse events were elevated ALT/AST caused by hepatitis, and pneumonitis (Supplementary Table S1). PD-L1 CPS scores showed no association with PFS (PFS of 4.6 vs 12.9 vs 3.5 months with CPS scores <1, 1-20 and >20, respectively (p=0.259, Supplementary Figure S3). [89Zr]Zr-DFO-durvalumab PET/CT dose finding In total, 14 patients were assigned to one of three dose cohorts: 2mg (n=4), 10mg (n=6), or 50mg (n=4) durvalumab. No clinically relevant infusion-related reactions for the injection with [89Zr]Zr-DFO-durvalumab were reported. Example [89Zr]Zr-DFO-durvalumab PET/CT-scans are shown in Figure 2. 5