Highlights

• Swiss researchers at PSI and University Hospital Basel are pioneering Terbium-161, the first radionuclide developed in Switzerland for clinical use, representing a major advancement beyond Lutetium-177 in precision oncology.
• Terbium-161's unique Auger electrons deliver lethal energy within single cancer cells, making it ideal for eliminating microscopic metastases that standard beta-emitters like Lutetium-177 might miss.
• Early clinical trials for neuroendocrine tumors and prostate cancer show Terbium-161 is significantly more potent than Lutetium-177, offering new hope for patients with disseminated microscopic disease or those who stopped responding to current therapies.

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While Lutetium-177 has revolutionized the landscape of precision oncology (see Rare Earths Enabling “Theranostics” on Rareearthexchanges.com), offering a lifeline to patients with advanced prostate and neuroendocrine cancers, innovation rarely rests on its laurels. In the quiet laboratories and busy hospital wards of Switzerland, a powerful successor is already emerging.

Researchers at the Paul Scherrer Institute (PSI) a (opens in a new tab)nd clinicians at the University Hospital Basel (opens in a new tab) are currently pioneering the transition to the "next" Lutetium: Terbium-161.¹

The "Swiss Made" Isotope

The development of Terbium-161 marks a significant milestone for Swiss science. It is the first time a new radionuclide has been developed in Switzerland specifically for clinical use.²

This breakthrough relies on a seamless collaboration between two powerhouses:³

• Paul Scherrer Institute (PSI): Located in Villigen, PSI acts as the engine of innovation.⁴ Here, teams led by researchers like Cristina Müller (opens in a new tab) and Nick van der Meulen (opens in a new tab) have spent over a decade perfecting the production and chemical separation of Terbium-161.⁵ Their unique facilities allow them to manufacture the isotope with the high purity required for human use.⁶
• University Hospital Basel: Serving as the clinical testing ground, the hospital translates this bench science into bedside therapy.⁷ Under the leadership of Prof. Damian Wild (opens in a new tab) and Prof. Roger Schibli (opens in a new tab) (who bridges both institutions), they have initiated world-first clinical trials to test the safety and efficacy of Terbium-161 in patients.⁸

Why Terbium-161? The "Auger" Advantage⁹

To understand why scientists are looking beyond Lutetium, one must look at the physics ofhow these isotopes kill cancer.

Lutetium-177 is a beta-emitter; it releases high-energy electrons that travel a few millimeters in tissue.¹⁰ This is excellent for destroying medium-to-large tumors, but it can be like using a shotgun: powerful, but with a spread that might miss microscopic disease or overshoot into healthy tissue.

Terbium-161 is different. While it also emits beta radiation (making it similar to Lutetium), it possesses a secret weapon: Auger electrons¹¹

• Precision Power: Auger electrons are extremely low-energy particles that travel very short distances—often less than the width of a single cell.¹²
• The "Double Tap": When Terbium-161 attaches to a cancer cell, it delivers its standard beta radiation plus a barrage of theseAuger electrons.¹³
• This deposits a massive amount of lethal energy directly into the cancer cell's nucleus, shredding its DNA.¹⁴
• Micrometastasis Hunter: Because Auger electrons have such a short range, they are theoretically perfect for eliminating "invisible" micrometastases and single circulating cancer cells that Lutetium might miss.¹⁵

From Lab to Life-Saving Therapy

The theoretical advantages are already showing clinical promise.¹⁶ In studies regarding neuroendocrine tumors and prostate cancer, Terbium-161 has demonstrated the potential to be significantly more potent than its predecessor.¹⁷

• Neuroendocrine Tumors: The PROGNOSTICS and other trial initiatives are investigating 161Tb-DOTA-LM3, a molecule designed to bind to tumor receptors more effectively than current standards.
• Prostate Cancer: With the success of Lutetium-PSMA therapy, the Swiss teams are testing 161Tb-PSMA. Early data suggest that for patients who have stopped responding to Lutetium, or for those with disseminated microscopic disease, Terbium could offer a new avenue of hope.¹⁸

A New Standard in the Making?

The work being done in Basel and Villigen is not just an incremental step; it represents a potential paradigm shift in nuclear medicine. By moving from Lutetium to Terbium, oncologists hope to transition from "managing" advanced cancer to actively hunting down the microscopic seeds of recurrence.¹⁹

As clinical trials progress, the world is watching. If Lutetium-177 was the breakthrough of the last decade, Terbium-161 is poised to be the precision instrument of the next, cementing Switzerland’s status as a global hub for radiopharmaceutical innovation.

Sources & Further Reading

Clinical Trials & Major Projects

• The PROGNOSTICS Project: A multi-institutional consortium (PSI, University Hospital Basel, ETH Zurich) focused on personalized Theragnostics for metastatic prostate cancer.
• Trial ID NCT05359146: Phase I study of Terbium-161 (161Tb-DOTA-LM3) for neuroendocrine tumors. University Hospital Basel.
• Trial ID NCT06343038: Phase I study of Terbium-161 (161Tb-SibuDAB) for metastatic prostate cancer. University Hospital Basel.

Key Publications

• First-in-Human Application: European Journal of Nuclear Medicine and Molecular Imaging (2024). Documented the first successful administration of Terbium-161 to a patient with a neuroendocrine tumor.
• Preclinical Comparison: Theranostics (2024). "Terbium radionuclides for theranostic applications," detailing the superior energy transfer of Auger electrons compared to standard Lutetium therapy.
• Foundation Study: EJNMMI (2019). The pivotal research by Müller et al. demonstrated Terbium-161's efficacy in prostate cancer models.

Institutional Press Releases

• Paul Scherrer Institute (March 11, 2024): "New nuclear medicine therapy successfully tested."
• Paul Scherrer Institute (Nov 22, 2023): "Terbium-161: new radionuclide therapy hits the clinic."
• University Hospital Basel: "Fighting tumors down to the last cancer cell" (PROGNOSTICS Project launch coverage).