Molecular theranostics: principles, challenges and controversies.

Theranostics is a new term for long-established principles in nuclear medicine. The generalisability of the term means there is a very broad use of the term across the medical literature, not all of which is consistent with the intent in nuclear medicine. The term molecular theranostics better reflects the philosophy and application in nuclear medicine. Even with a clearer definition, there are a number of challenges or controversies whose debate provides a richer understanding of the principles and applications of molecular theranostics. Radioiodine imaging and therapy of hyperthyroidism and thyroid cancer provide the historical context for theranostics. The prototype molecular theranostic is the ⁶⁸Ga/¹⁷⁷Lu DOTATATE pair that targets somatostatin receptor subtype 2 in neuroendocrine tumors. The potential value of precision medicine of radiation dosimetry in molecular theranostics needs a balanced discussion with limitations of reactive dosimetry and the opportunities for predictive or pre-treatment dosimetry. Despite challenges and limitations, molecular theranostics is a powerful tool in the precision medicine landscape. Molecular theranostics is a vehicle for improved outcomes in cancer patients with a future-facing portfolio of opportunities.