Hunter Stephens

In recent years, radioligand therapy programs have entered the clinic following a familiar path: borrowing organ dose limits from external beam radiotherapy (EBRT), and escalating activity levels until reaching or slightly exceeding these EBRT thresholds in organs such as kidneys. In August 2025, the FDA signaled that these approaches alone are no longer sufficient.

Measuring absorbed dose is essential. But it cannot tell you whether a dosing regimen is optimal, whether an organ limit is biologically relevant, or whether the same regimen will perform consistently across patients. Those questions sit at the heart of dose optimization in radiopharmaceutical therapy, and increasingly at the center of regulatory expectations.

This review focuses on the development of radiopharmaceutical imaging agents and radioligand therapeutics for paediatric use. Nuclear medicine plays an important role in the diagnosis and treatment of various childhood conditions, including cancers, infections and brain disorders. It assesses organ function alongside structure, allowing for earlier and more specific diagnoses, crucial in children where symptoms can be nonspecific.