PARP PET

PARP PET uses radiolabelled analogues of the PARP inhibitors olaparib and rucaparib, such as 18F-FluorThanatrace (FTT, Penn) and 18F-PARPi (MSK), which bind PARP1 in the nucleus and so measure both expression of the enzyme and drug engagement at the target. The rationale is that genomic HRD tests read a permanent scar, whereas a PARP tracer reports the tumour's current state. Trials in ovarian, breast and head-and-neck cancer test whether uptake predicts benefit from PARP inhibitors beyond BRCA and HRD status, and whether a fall in uptake on treatment confirms target engagement. It offers a direct pharmacodynamic readout that complements genomic HRD, but remains at the research stage and is available at only a few academic sites. It is a scan that measures how much of the DNA repair enzyme a tumour has, to predict whether a PARP inhibitor will work.