BACKGROUND AND PURPOSE: PET imaging of cetuximab uptake may help selecting cancer patients with the highest chance of benefit. The aim of this phase I trial was to determine the safety of the tracer (89)Zr-cetuximab and to assess tumour uptake.
METHODS: Two dose schedules were used; two consecutive doses of 60MBq (89)Zr-cetuximab or a single dose of 120MBq, both preceded by 400mg/m(2) of unlabelled cetuximab. Toxicity (CTCAE 3.0) was scored twice weekly. PET-CT scans were acquired on days 4, 5 and 6 (step 1) or 5, 6, 7 (step 2). Because tumour uptake could not be assessed satisfactorily, a third step was added including EGFR overexpressing tumours.
RESULTS: Nine patients were included (6 NSCLC; 3 HNC). No additional toxicity was associated with administration of (89)Zr-cetuximab compared to standard cetuximab. A tumour to blood ratio (TBR)>1 was observed in all but one patient, with a maximum of 4.56. TBR was not different between dose schedules. There was a trend for higher TBR at intervals>5days after injection.
CONCLUSIONS: Both presented (89)Zr-cetuximab administration schedules are safe. The recommended dose for future trials is 60MBq, with a minimum time interval for scanning of 6days.