Targeted molecular imaging: the path to smarter patient stratification and personalized treatment

Positron emission tomography (PET), using radiolabelled mAbs, antibody fragments or engineered protein scaffolds (immuno-PET), has the potential to acquire information non-invasively and can be highly complementary to analyses based on tissue acquisition. Accordingly, immuno-PET agents might accurately identify the presence and accessibility of the target and provide a rapid assessment of tumour response to a variety of treatments in a timely fashion (e.g. within 1-2 weeks of treatment initiation). Furthermore, immuno-PET agents can provide information about the heterogeneity of both target expression and therapeutic response, which are increasingly recognised as key factors in treatment resistance. This especially relates to patients with advanced disease in whom target expression may vary from site to site and a biopsy of a single local or metastatic deposit may not accurately reflect the situation across the entire disease burden. Although introduction of immuno-PET into routine clinical practice may add complexity and increase costs, with appropriate use this imaging modality has the potential to identify patients likely to benefit from therapy and assess the efficacy of novel target-specific drugs. During drug development, this might minimise the wasted expense of taking ineffective treatments through further clinical testing and, for approved drugs, this might reduce futile ineffective therapy in patients whose tumours are likely to display intrinsic or acquired resistance.