The lowest injected mass (0.04 μg) in this study resulted in tumour uptake of 3.8 ± 1.1 and 3.6 ± 1.2%ID/g for U251MG and U87MG xenografts, respectively, similar to previous reports on other radiolabelled PARP inhibitors [16, 17]. Here, PARP1 is linked to neoplasm.