Radiosynoviorthesis of knees by means of 166Ho-holmium-boro-macroaggregates

The various therapeutic applications of the medical isotope holmium-166: a narrative review

Over the years, a broad spectrum of applications of the radionuclide holmium-166 as a medical isotope has been established. The isotope holmium-166 is attractive as it emits high-energy beta radiation which can be used for a therapeutic effect and gamma radiation which can be used for nuclear imaging purposes. Furthermore, holmium-165 can be visualized by MRI because of its paramagnetic properties and by CT because of its high density. Since holmium-165 has a natural abundance of 100%, the only by-product is metastable holmium-166 and no costly chemical purification steps are necessary for production of nuclear reactor derived holmium-166. Several compounds labelled with holmium-166 are now used in patients, such Ho¹⁶⁶-labelled microspheres for liver malignancies, Ho¹⁶⁶-labelled chitosan for hepatocellular carcinoma (HCC) and [¹⁶⁶Ho]Ho DOTMP for bone metastases. The outcomes in patients are very promising, making this isotope more and more interesting for applications in interventional oncology. Both drugs as well as medical devices labelled with radioactive holmium are used for internal radiotherapy. One of the treatment possibilities is direct intratumoural treatment, in which the radioactive compound is injected with a needle directly into the tumour. Numerous other applications have been developed, like patches for treatment of skin cancer and holmium labelled antibodies and peptides. The second major application that is currently clinically applied is selective internal radiation therapy (SIRT, also called radioembolization), a novel treatment option for liver malignancies. This review discusses medical drugs and medical devices based on the therapeutic radionuclide holmium-166.

Radiosynoviorthesis (RSO): influencing factors and therapy monitoring

OBJECTIVE

To evaluate the effectiveness of radiosynoviorthesis (RSO) in relation to joint type and underlying disease by both self-assessment of patients and scintigraphic assessment to determine conditions under which RSO might be preferable to the sole intra-articular corticoid injection.

METHODS

Radiosynoviorthesis was performed on 136 patients for 424 joints [242 small, 130 medium-sized, and 52 large joints; 313 with rheumatoid arthritis (RA) and 111 with osteoarthritis (OA)]. The success of RSO was evaluated after 12 months by patients' estimation, and in 35 patients for 157 joints additionally by two-phase bone scintigraphy. The relative change in the scintigraphic uptake was compared with the patients' estimation.

RESULTS

The subjectively estimated success rates for the small, medium-sized, and large joints were 89% (215/242), 86% (112/130), and 79% (41/52), and for RA and OA 89% (280/313) and 79% (88/111), respectively. The scintigraphically determined response rates for small and medium-sized joints were 81% (86/106) and 69% (35/51), respectively. There was a mismatch between patients' assessment and scintigraphic assessments in 18% (28/157) with 6 false-negative and 22 false-positive estimations using scintigraphy as the standard of reference.

CONCLUSIONS

The success of RSO is higher in patients with RA than in patients with OA. For the finger, ankle, and wrist joints in RA, RSO is so promising that we would like to advocate its preference over the sole intraarticular corticoid injection. Perfusion bone scintigraphy can be used for therapy monitoring and earlier switching to RSO by showing that other therapies have failed.