Thulium-170-labeled microparticles for local radiotherapy: preliminary studies

Area of Science:

• Nuclear medicine
• Radiopharmaceutical science
• Biomaterials

Background:

• Radiation synovectomy (RSV) is a treatment for inflammatory joint conditions.
• Developing effective and safe radiopharmaceuticals is crucial for targeted therapies.
• Thulium-170 ((170)Tm) offers suitable properties for brachytherapy applications.

Purpose of the Study:

• To prepare and characterize Thulium-170 labeled tin oxide microparticles.
• To evaluate the biological safety and efficacy of these microparticles for radiation synovectomy.
• To assess the potential of (170)Tm-microparticles for local antitumor therapy.

Main Methods:

• Production of (170)Tm via neutron irradiation of thulium oxide.
• Synthesis of (170)Tm-labeled tin oxide microparticles with high yield and purity.
• Characterization of particle size, morphology, and in vitro stability.
• Intra-articular injection into Beagle dog knee joints for in vivo evaluation.
• SPECT and SPECT-CT imaging for tracking particle distribution and leakage up to 9 months.

Main Results:

• Successfully synthesized (170)Tm-labeled tin oxide microparticles with >99% radionuclidic purity and excellent in vitro stability.
• Particles exhibited stable spherical morphology (1.4-3.2 μm).
• In vivo studies showed minimal leakage (<8% of instilled dose) from the joint over 9 months.
• Leaked particles primarily localized to inguinal lymph nodes.
• No adverse radiotoxicological effects were observed in the animal model.

Conclusions:

• 170Tm-labeled tin oxide microparticles are a promising, non-toxic radiopharmaceutical candidate for radiation synovectomy.
• The formulation demonstrates good retention in the joint, minimizing systemic exposure.
• Further investigation is warranted for its application in local antitumor therapy.