Is Dosimetry done after Tb161 Administration?

Dosimetry in Terbium-161 Therapy: Personalizing Radiation, Minimizing Toxicity

Terbium-161 (Tb-161) is a next-generation beta-emitting radionuclide under clinical investigation for treating metastatic castration-resistant prostate cancer (mCRPC). A key strength of Tb-161 lies in its compatibility with precision dosimetry, which allows clinicians to measure and adjust radiation dose delivery after each therapy cycle, enhancing safety and treatment outcomes.

Since Tb-161 is a beta emitter with gamma emissions suitable for imaging, accurate dosimetry is feasible using SPECT/CT. In the ongoing 
VIOLET trial (https://clinicaltrials.gov/study/NCT05521412), post-therapy scans are performed after every treatment cycle at 4, 24, and 96 hours using advanced imaging. These scans generate patient-specific dose maps, showing how much radiation reaches tumors and critical organs like the salivary glands, kidneys, and bone marrow.

This personalized approach to dosimetry helps physicians adjust the next dose precisely.

https://pmc.ncbi.nlm.nih.gov/articles/PMC10945337,

Tb-161 delivers approximately 35–40% more energy per decay than Lu-177 and includes Auger and conversion electrons, which are more lethal to micrometastases while sparing normal tissue. Without dosimetry, this therapeutic gain could be lost or cause unintended toxicity. With dosimetry, clinicians can balance these benefits with real-time safety oversight.

Dosimetry in Tb-161 therapy transforms one-size-fits-all cancer treatment into a tailored approach—delivering the right dose to the right place while protecting organs at risk. This level of customization makes Tb-161 not only more effective but also potentially safer than traditional radioligand therapies.

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