Theranostics is an area of medicine that integrates diagnosis and therapeutics, representing a powerful step forwards in the transition from conventional “trial and error” medicine to a medicine that is more targeted, predictive, translational and therefore more personalized.

Advancements in molecular therapeutics, in vitro diagnosis and technologies such as biosensing are speeding up the pursuit of “smart” drugs that can detect unhealthy cells, attach to them and deliver cytotoxic cargo that destroys them, a strategy that is of particular interest in oncology.

Recent developments in molecular biology, proteomics and genetics have significantly enriched understanding of tumor biochemistry and function, including identification of the receptors tumor cells express. In theranostics, these molecular targets can be used to access tumors, image the disease area and deliver targeted cytotoxic substances directly to tumor tissue.

In position emission tomography (PET) and single-photon emission computed tomography (SPECT) imaging applications, molecular targets can be combined with radiotracers for both diagnostic and therapeutic purposes. Diagnostic imaging is performed to determine tumor size, classification and stage so that localized radiation can be administered specifically to the diseased area, without damaging any surrounding healthy cells.

A radioactive compound is added to a linking molecule on another molecule that binds to a cancer cell. Since gamma radiation is high energy and can pass through the body, it can be detected externally, meaning tracers that emit this radiation are used for diagnosis. Beta radiation is medium energy and can travel short distances within the body, so tracers that emit this radiation are used to deliver therapy.

A lack of affordable radiotracers has prevented widespread uptake of theranostics and the approach is currently mainly limited to neuroendocrine tumors. The development of new radiotracers is therefore at the forefront of preclinical imaging research, which aims to free up theranostics as a tool for many other types of cancer.