Radiopharmaceutical Delivery for Theranostics: Pharmacokinetics and Pharmacodynamics

Theranostics is a new and evolving combination diagnostic and/or therapeutic approach that is demonstrating efficacy for treatment of a growing number of cancers. In this approach, a diagnostic radiopharmaceutical is used in concert with positron-emission tomography (PET) or single photon emission computed tomography (SPECT) imaging to identify whether a cancer-specific membrane protein is strongly expressed on a patient's tumors. If the molecular target is detected with sufficient specificity and uptake, a therapeutic radiopharmaceutical, nearly identical to the diagnostic radiopharmaceutical except labeled with a longer-lived alpha or beta-emitting radionuclide, is administered at a therapeutic dose level to treat the cancer. Quantitative imaging methods are being used to elucidate patient-specific pharmacokinetics to select patients for whom the therapeutic radiopharmaceutical would be most beneficial. Similarly, quantitative imaging of the therapeutic radionuclide is being used to image pharmacodynamic response to therapy (cell kill) to guide personalized, patient-specific dosages designed to both reduce radiation toxicities and optimize radiotherapeutic benefit.