Targeted radionuclide therapy: an emerging field in solid tumours

Purpose of review Targeted radionuclide therapy (TRNT) is characterized by systemic administration of radiolabelled drugs, targeting specific molecular alterations expressed on the tumour cells. Small molecules, labelled with beta- or alpha- emitting radioisotopes, are used to deliver radiation directly to the tumour sites. Pretreatment imaging to visualize whole body biodistribution of the target, using the same drugs labelled with positron or gamma-emitting radionuclides, completes the concept of theranostic. This review will briefly summarize the current clinical research findings and applications of TRNT in solid tumours, mostly focusing on neuroendocrine and prostate neoplasms. Recent findings Peptide receptor radionuclide therapy is a major component in the management of gastroentropancreatic neuroendocrine tumours, with favourable safety profile, quality-of-life improvement and survival benefit. On the NETTER-1 study, it proved to be more effective than high-dose long-acting-release octreotide, leading to its regulatory approval. Prostate-specific membrane antigen (PSMA) is an excellent target for TRNT in prostate cancer. Lu-177-PSMA radioligand therapy demonstrated higher response rates in patients with metastatic castration resistant prostate cancer, when compared with second-line chemotherapy. New developments, including targeting of fibroblast activation proteins overexpressed in the tumour stroma, show promising preliminary results in the theranostic setting. Recent research has demonstrated and consolidated the use of TRNT against well established targets in neuroendocrine tumours and prostate cancer. The identification of new promising molecular targets for TRNT, will further expand the theranostic applications of radionuclides in the field of nuclear medicine.