Radiation Dosimetry in Theranostics: A Review

Theranostics refers to the combination of therapy and diagnostics in a single clinical entity or approach. Theranostics is particularly adaptable to radiopharmaceutical therapy (RPT) based on the unique ability to scintigraphically image radiopharmaceuticals in vivo and thereby noninvasively measure their time-dependent activities in and among target lesions and normal organs. Theranostics with personalized RPT, based on the maximum tolerated dose to the therapy-limiting tissue or the prescribed dose to the target tissue, offers the important advantages of lower toxicity or greater efficacy compared with fixed-administered-activity RPT but requires rather time-consuming, technically challenging patient measurements and analyses. Importantly, however, the perceived obstacles to dosimetry-based RPT have been or are being largely overcome. Further, the currently available dose-response data, though still rather limited, indicate that patient-specific dosimetry may help optimize RPT by minimizing toxicity or maximizing efficacy. Additional dose-response data from prospective multicenter trials are still required to definitively establish the value of patient-specific dosimetry in RPT. Such trials will require standardization of calibration procedures, acquisition protocols, and reconstruction methods among participating institutions.