Evaluation of the Safety and Feasibility of Same-Day Holmium-166 -Radioembolization Simulation and Treatment of Hepatic Metastases.

PURPOSE: To evaluate the safety and feasibility of same-day treatment, including the simulation procedure for assessment of intrahepatic and extrahepatic distribution of the microspheres, with holmium-166 (166Ho)-radioembolization. MATERIALS AND METHODS: This was a secondary analysis of patients included in the 4 prospective studies (HEPAR I, HEPAR II, HEPAR PLuS, and SIM) on 166Ho-radioembolization. The technical success rate of the same-day treatment protocol, defined as the number of patients who completed the same-day treatment, was measured. Total in-room time, duration of the scout procedure, time to imaging, and duration of the treatment procedure were recorded. Reasons for discontinuation or adjustment of treatment were identified. Adverse events that occurred during the treatment day were recorded. RESULTS: One hundred five of 120 scheduled patients completed the same-day treatment with 166Ho-radioembolization (success rate, 88%). After the simulation procedure, treatment was cancelled in 15 patients because of extrahepatic deposition (n = 8), suboptimal tumor targeting (n = 1), unanticipated vascular anatomy (n = 5), and dissection (n = 1). In another 14 patients, the treatment plan was adjusted. The median total procedure time (ie, simulation, imaging, and treatment) was 6:39 hours:minutes (range, 3:58-9:17 hours:minutes). Back pain was a major same-day treatment-related complaint (n = 28). CONCLUSION: 166Ho-radioembolization as a same-day treatment procedure is feasible in most selected patients, although treatment was adjusted in 12% of patients and cancelled in 12% of patients. This approach might be beneficial for a select patient population, such as patients needing a radiation segmentectomy.

Ir-Ho bimetallic complex-mediated low-dose radiotherapy/radiodynamic therapy in vivo.

We report a bimetallic complex [Ir4Ho2(pq)8(H2dcbpy)4(OAc)2] (denoted as Ir4Ho2, pq = 2-phenylquinoline, H2dcppy = 2,2'-bipyridine-3,3'-dicarboxylic acid) and its application for radiotherapy/radiodynamic therapy (RT/RDT). In a tumor xenograft mouse model, Ir4Ho2 exerted a tumor-suppressive effect through efficient low-dose RT/RDT.

Development and characterisation of polymeric microparticle of poly(d,l-lactic acid) loaded with holmium acetylacetonate.

Biodegradable polymers containing radioactive isotopes such as Holmium 166 (166Ho) have potential applications as beta particle emitters in tumour tissues. It is also a gamma ray emitter, allowing nuclear imaging of any tissue to be acquired. It is frequently used in the form of complexes such as holmium acetylacetonate (HoAcAc), which may cause damages in tissues next to the targets cancer cells, as it is difficult to control its linkage or healthy tissues radiotherapy effects. Poly(d,l-lactic acid), PDLLA, was used to encapsulate holmium acetylacetonate (HoAcAc) using an emulsion solvent extraction/evaporation technique. Microspheres with sizes between 20-53 µm were extensively characterised. HoAcAc release from the microspheres was assessed through studies using Inductively Coupled Plasma - Optical Emission Spectroscopy, and the microspheres showed no holmium leakage after a period of 10 half-lives and following gamma irradiation. Thus, HoAcAc loaded microspheres are here presented as a potential system for brachytherapy and imaging purposes.

Intratumoral injection of radioactive holmium-166 microspheres in recurrent head and neck squamous cell carcinoma: preliminary results of first use.

BACKGROUND: Limited treatment options exist for patients with locoregional recurrences of head and neck squamous cell carcinoma (HNSCC). In the palliative setting, a single session, minimally invasive, and relatively safe therapy is desirable. This case series illustrates the feasibility of a direct intratumoral injection of radioactive holmium-166 microspheres (HoMS) in patients as a palliative treatment for recurrent HNSCC. PATIENTS AND METHODS: In this retrospective analysis, patients with already reirradiated irresectable recurrent HNSCC, for whom palliative chemotherapy was unsuccessful or impossible, were offered microbrachytherapy with HoMS. The intratumoral injection was administered manually under ultrasound guidance. Parameters scored were technical feasibility (i.e. administration, leakage, and distribution), clinical response (response evaluation criteria in solid tumors 1.1), and complications (Common Terminology Criteria for Adverse Events 4.3). RESULTS: From 2015 to 2017, three patients were treated. None of the patients experienced adverse events; however, therapeutic effects were minimal. Technical difficulties, including precipitating of microspheres and high intratumoral pressure, resulted in suboptimal distribution of the microspheres. CONCLUSION: Intratumoral injections with HoMS are minimally invasive and relatively safe in palliation of HNSCC patients. Careful patient selection and improved administration techniques are required to provide a more effective treatment. Further investigation of this novel treatment modality should be carried out because of the absence of side effects and lack of other treatment options.

Intratumoral injection of radioactive holmium ( 166 Ho) microspheres for treatment of oral squamous cell carcinoma in cats.

BACKGROUND & AIMS: A "microbrachytherapy" was developed as treatment option for inoperable tumours by direct intratumoral injection of radioactive holmium-166 ( 166 Ho) microspheres (MS). 166 Ho emits ß-radiation which potentially enables a high, ablative, radioactive-absorbed dose on the tumour tissue while sparing surrounding tissues. MATERIALS & METHODS: Safety and efficacy of 166 Ho microbrachytherapy were evaluated in a prospective cohort study of 13 cats with inoperable oral squamous cell carcinoma without evidence of distant metastasis. RESULTS: Local response rate was 55%, including complete response or partial response (downstaging) enabling subsequent marginal resection. Median survival time was 113 days overall, and 296 days for patients with local response. Side effects were minimal. Tumour volume was a significant predictor of response. DISCUSSION: Response rate may be further improved by optimizing the intratumoral spatial distribution of 166 Ho MS. CONCLUSION: 166 Ho microbrachytherapy has potential as a minimally invasive, single procedure radio-ablation treatment of unresectable tumours with minimal morbidity.

Surefire infusion system versus standard microcatheter use during holmium-166 radioembolization: study protocol for a randomized controlled trial.

BACKGROUND: An anti-reflux catheter (ARC) may increase the tumor absorbed dose during radioembolization (RE) by elimination of particle reflux and its effects on hemodynamics. Since the catheter is fixed in a centro-luminal position, it may also increase the predictive accuracy of a scout dose administration before treatment. The purpose of the SIM trial is to compare the effects of ARC use during RE with holmium-166 (166Ho) microspheres in patients with colorectal liver metastases (CRLM), with the use of a standard end-hole microcatheter. METHODS/DESIGN: A within-patient randomized controlled trial (RCT) will be conducted in 25 patients with unresectable chemorefractory liver-dominant CRLM. Study participants will undergo a 166Ho scout dose procedure in the morning and a therapeutic procedure in the afternoon. The ARC will be randomly allocated to the left/right hepatic artery, and a standard microcatheter will be used in the contralateral artery. SPECT/CT imaging will be performed for quantitative analyses of the microsphere distribution directly after the scout and treatment procedure. Baseline and follow-up investigations include 18F-FDG-PET + liver CT, clinical and laboratory examinations. The primary endpoint is the comparison of tumor to non-tumor (T/N) activity ratio in both groups. Secondary endpoints include comparisons of mean absorbed dose in tumors and healthy liver tissue, infusion efficiency, the predictive value of 166Ho scout dose for tumor response. In the entire cohort, a dose-response relationship, clinical toxicity, and overall survival will be assessed. The sample was determined for the expectation that the ARC will increase the T/N ratio by 25 % (mean T/N ratio 2.0 vs. 1.6). DISCUSSION: The SIM trial is a within-patient RCT that will assess whether 166Ho RE treatment can be optimized by using an ARC. TRIAL REGISTRATION: The SIM trial is registered at clinicaltrials.gov ( NCT02208804 ). Registered on 31 July 2014.

Chemoradiotherapeutic Magnetic Nanoparticles for Targeted Treatment of Nonsmall Cell Lung Cancer.

Lung cancer is the leading cause of cancer-related death in the United States and approximately 85% of all lung cancers are classified as nonsmall cell (NSCLC). We here use an innovative approach that may ultimately allow for the clinician to target tumors and aggressively reduce tumor burden in patients with NSCLC. In this study, a platinum (Pt)-based chemotherapeutic (cisplatin, carboplatin, or oxaliplatin) and holmium-165 (Ho), which can be neutron-activated to produce the holmium-166 radionuclide, have been incorporated together in a garnet magnetic nanoparticle (HoIG-Pt) for selective delivery to tumors using an external magnet. The synthesized magnetic HoIG nanoparticles were characterized using PXRD, TEM, ICP-MS, and neutron-activation. Platinum(II) drugs were incorporated onto HoIG, and these were characterized using FTIR, EDX, ICP-MS, and zeta potential measurements, and in vitro and in vivo studies were performed using a HoIG-platinum system. Results indicate that neutron-activated (166)HoIG-cisplatin is more toxic toward NSCLC A549 cells than is blank (166)HoIG and free cisplatin, and that when an external magnetic field is applied in vivo, higher tumor to liver ratios of Ho are observed than when no magnet is applied, suggesting that magnetic targeting is achieved using this system. Furthermore, an efficacy study demonstrated the inhibition of tumor growth by chemoradiotherapeutic magnetic nanoparticles, compared to no treatment controls.

Radiotherapeutic bandage based on electrospun polyacrylonitrile containing holmium-166 iron garnet nanoparticles for the treatment of skin cancer.

Radiation therapy is used as a primary treatment for inoperable tumors and in patients that cannot or will not undergo surgery. Radioactive holmium-166 ((166)Ho) is a viable candidate for use against skin cancer. Nonradioactive holmium-165 ((165)Ho) iron garnet nanoparticles have been incorporated into a bandage, which, after neutron-activation to (166)Ho, can be applied to a tumor lesion. The (165)Ho iron garnet nanoparticles ((165)HoIG) were synthesized and introduced into polyacrylonitrile (PAN) polymer solutions. The polymer solutions were then electrospun to produce flexible nonwoven bandages, which are stable to neutron-activation. The fiber mats were characterized using scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis and inductively coupled plasma mass spectrometry. The bandages are stable after neutron-activation at a thermal neutron-flux of approximately 3.5 × 10(12) neutrons/cm(2)·s for at least 4 h and 100 °C. Different amounts of radioactivity can be produced by changing the amount of the (165)HoIG nanoparticles inside the bandage and the duration of neutron-activation, which is important for different stages of skin cancer. Furthermore, the radioactive bandage can be easily manipulated to irradiate only the tumor site by cutting the bandage into specific shapes and sizes that cover the tumor prior to neutron-activation. Thus, exposure of healthy cells to high energy ß-particles can be avoided. Moreover, there is no leakage of radioactive material after neutron activation, which is critical for safe handling by healthcare professionals treating skin cancer patients.

Intratumoral administration of holmium-166 acetylacetonate microspheres: antitumor efficacy and feasibility of multimodality imaging in renal cancer.

PURPOSE: The increasing incidence of small renal tumors in an aging population with comorbidities has stimulated the development of minimally invasive treatments. This study aimed to assess the efficacy and demonstrate feasibility of multimodality imaging of intratumoral administration of holmium-166 microspheres ((166)HoAcAcMS). This new technique locally ablates renal tumors through high-energy beta particles, while the gamma rays allow for nuclear imaging and the paramagnetism of holmium allows for MRI. METHODS: (166)HoAcAcMS were administered intratumorally in orthotopic renal tumors (Balb/C mice). Post administration CT, SPECT and MRI was performed. At several time points (2 h, 1, 2, 3, 7 and 14 days) after MS administration, tumors were measured and histologically analyzed. Holmium accumulation in organs was measured using inductively coupled plasma mass spectrometry. RESULTS: (166)HoAcAcMS were successfully administered to tumor bearing mice. A striking near-complete tumor-control was observed in (166)HoAcAcMS treated mice (0.10±0.01 cm(3) vs. 4.15±0.3 cm(3) for control tumors). Focal necrosis and inflammation was present from 24 h following treatment. Renal parenchyma outside the radiated region showed no histological alterations. Post administration CT, MRI and SPECT imaging revealed clear deposits of (166)HoAcAcMS in the kidney. CONCLUSIONS: Intratumorally administered (166)HoAcAcMS has great potential as a new local treatment of renal tumors for surgically unfit patients. In addition to strong cancer control, it provides powerful multimodality imaging opportunities.

Holmium nanoparticles: preparation and in vitro characterization of a new device for radioablation of solid malignancies.

PURPOSE: The present study introduces the preparation and in vitro characterization of a nanoparticle device comprising holmium acetylacetonate for radioablation of unresectable solid malignancies. METHODS: HoAcAc nanoparticles were prepared by dissolving holmium acetylacetonate in chloroform, followed by emulsification in an aqueous solution of a surfactant and evaporation of the solvent. The diameter, surface morphology, holmium content, and zeta potential were measured, and thermal behavior of the resulting particles was investigated. The stability of the particles was tested in HEPES buffer. The r(2)* relaxivity of protons and mass attenuation coefficient of the nanoparticles were determined. The particle diameter and surface morphology were studied after neutron activation. RESULTS: Spherical particles with a smooth surface and diameter of 78 ± 10 nm were obtained, and the particles were stable in buffer. Neutron irradiation did not damage the particles, and adequate amounts of activity were produced for nuclear imaging and radioablation of malignancies through intratumoral injections. CONCLUSIONS: The present study demonstrates that HoAcAc nanoparticles were prepared using a solvent evaporation process. The particle diameter can easily be adapted and can be optimized for specific therapeutic applications and tumor types.

Gamma spectrometry and chemical characterization of ceramic seeds with samarium-153 and holmium-166 for brachytherapy proposal.

Ceramic seeds were synthesized by the sol-gel technique with Si:Sm:Ca and Si:Ho:Ca. One set of seeds was irradiated in the TRIGA type nuclear reactor IPR-R1 and submitted to instrumental neutron activation analysis (INAA), K(0) method, to determine mass percentage concentration of natural samarium and holmium in the seed as well as to determine all existing radionuclides and their activities. Attention was paid to discrimination of Si-31, Ca-40, Ca-45, Ca-47, Ca-49, Sm-145, Sm-155, Sm-153 and Ho-166. A second sample was submitted to atomic emission spectrometry (ICP-AES) also to determine samarium and holmium concentrations in weight. A third sample was submitted to X-ray fluorescence spectrometry to qualitatively determine chemical composition. The measured activity was due to Sm-153 and Ho-166 with a well-characterized gamma spectrum. The X-ray fluorescence spectrum demonstrated that there is no discrepancy in seed composition. The maximum ranges in the water of beta particles from Sm-153 and Ho-166 decay were evaluated, as well as the dose rate and total dose delivered within the volume delimited by the range of the beta particles. The results are relevant for investigation of the viability of producing Sm-153 and Ho-166 radioactive seeds for use in brachytherapy.

Microspheres with ultrahigh holmium content for radioablation of malignancies.

PURPOSE: The aim of this study was to develop microspheres with an ultra high holmium content which can be neutron activated for radioablation of malignancies. These microspheres are proposed to be delivered selectively through either intratumoral injections into solid tumors or administered via an intravascularly placed catheter. METHODS: Microspheres were prepared by solvent evaporation, using holmium acetylacetonate (HoAcAc) crystals as the sole ingredient. Microspheres were characterized using light and scanning electron microscopy, coulter counter, titrimetry, infrared and Raman spectroscopy, differential scanning calorimetry, X-ray powder diffraction, magnetic resonance imaging (MRI), and X-ray computed tomography (CT). RESULTS: Microspheres, thus prepared displayed a smooth surface. The holmium content of the HoAcAc microspheres (44% (w/w)) was higher than the holmium content of the starting material, HoAcAc crystals (33% (w/w)). This was attributed to the loss of acetylacetonate from the HoAcAc complex, during rearrangement of acetylacetonate around the holmium ion. The increase of the holmium content allows for the detection of (sub)microgram amounts of microspheres using MRI and CT. CONCLUSIONS: HoAcAc microspheres with an ultra-high holmium content were prepared. These microspheres are suitable for radioablation of tumors by intratumoral injections or treatment of liver tumors through transcatheter administration.

Phase II study of transarterial holmium-166-chitosan complex treatment in patients with a single, large hepatocellular carcinoma.

PURPOSE: Holmium-166 ((166)Ho) is a neutron-activated radioactive isotope whose effectiveness in hepatocellular carcinoma (HCC) was first reported in a preclinical study in 1991. Chitosan is a polymer of 2-deoxy-2-amino-D-glucose that readily forms a chelate with heavy metals and converts from a solution under acidic conditions into a gel under neutral or basic conditions. We performed a prospective trial of a transarterial administration of a radiopharmaceutical (166)Ho-chitosan complex in patients with single, large HCC. PATIENTS AND METHODS: The study involved 54 patients who had single HCC (>or=3 cm) without a vascular shunt and were either inoperable or refused surgery. The (166)Ho-chitosan complex was administered at a dose of 20 mCi per cm of tumor diameter (capping at 200 mCi) via the artery that directly fed the tumor. RESULTS: The median tumor size was 5.3 cm (range: 3-13 cm). The response rate was 78% (42/54), and 31 patients had a complete response for a median duration of 27 months. The incidence of grade 3 or 4 leukopenia was 18.6%, anemia 7.4%, thrombocytopenia 27.8%, AST/ALT elevation 26%/24%, and total bilirubin elevation 5.6%. There were two treatment-related deaths (3.7%). Subset analysis revealed a substantial difference between the two groups categorized by tumor size (3-5 vs. >5 cm) with respect to response rate (p = 0.004) and overall survival (p = 0.02). CONCLUSION: We found that transarterial administration of the (166)Ho-chitosan complex was highly effective in the treatment of HCC with acceptable toxicities, especially for patients with tumors of 3-5 cm.

Clinical effects of transcatheter hepatic arterial embolization with holmium-166 poly(L-lactic acid) microspheres in healthy pigs.

PURPOSE: The aim of this study is to evaluate the toxicity of holmium-166 poly(L-lactic acid) microspheres administered into the hepatic artery in pigs. METHODS: Healthy pigs (20-30 kg) were injected into the hepatic artery with holmium-165-loaded microspheres ((165)HoMS; n=5) or with holmium-166-loaded microspheres ((166)HoMS; n=13). The microspheres' biodistribution was assessed by single-photon emission computed tomography and/or MRI. The animals were monitored clinically, biochemically, and ((166)HoMS group only) hematologically over a period of 1 month ((165)HoMS group) or over 1 or 2 months ((166)HoMS group). Finally, a pathological examination was undertaken. RESULTS: After microsphere administration, some animals exhibited a slightly diminished level of consciousness and a dip in appetite, both of which were transient. Four lethal adverse events occurred in the (166)HoMS group due either to incorrect administration or comorbidity: inadvertent delivery of microspheres into the gastric wall (n=2), preexisting gastric ulceration (n=1), and endocarditis (n=1). AST levels were transitorily elevated post-(166)HoMS administration. In the other blood parameters, no abnormalities were observed. Nuclear scans were acquired from all animals from the (166)HoMS group, and MRI scans were performed if available. In pigs from the (166)HoMS group, atrophy of one or more liver lobes was frequently observed. The actual radioactivity distribution was assessed through ex vivo (166m)Ho measurements. CONCLUSION: It can be concluded that the toxicity profile of HoMS is low. In pigs, hepatic arterial embolization with (166)HoMS in amounts corresponding with liver-absorbed doses of over 100 Gy, if correctly administered, is not associated with clinically relevant side effects. This result offers a good perspective for upcoming patient trials.

[High-power holmium laser with percutaneous nephrolithotripsy for kidney calculi].

OBJECTIVE: To assess the efficacy and safety of the high-power holmium laser with percutaneous nephrolithotripsy for kidney calculi. METHODS: The high-power (60 W: 3.0 J x 20 Hz) holmium laser with percutaneous nephrolithotripsy was performed on 52 patients with single kidney pelvic or calyceal stones (average stone diameter 3.1 cm), 36 patients with multi-kidney pelvic and calyceal stones (average diameter 2.8 cm), 24 patients with staghorn stones (average diameter 6.8 cm). The duration of stone surgery, stone-free rate and complication were assessed. RESULTS: The mean duration of stone surgery was 44 min, the stone-free rate was 66% (74/112) after the first session, 89% (100/112) at the end of session. 3 patients had high fever after percutaneous nephrolithotripsy, no other adverse events were noted. CONCLUSIONS: The high-power holmium laser with percutaneous nephrolithotripsy can fragments calculi quickly and reduces the length of time of operation. It is an effective and safe technique for kidney calculi.

Effective local control of prostate cancer by intratumoral injection of (166)Ho-chitosan complex (DW-166HC) in rats.

PURPOSE: The aim of this study was to evaluate the therapeutic effect and morphological alterations resulting from (166)Ho-chitosan complex (DW-166HC) in an animal model of prostate cancer. METHODS: First, in a subcutaneous tumor model, 80 rats were randomly divided into four groups (n=20 in each group), and intratumoral injections of 0.05 ml (normal saline in group 1,( 165)Ho-chitosan complex solution in group 2, DW-166HC solution (10 mCi) in group 3, and DW-166HC solution (20 mCi) in group 4) were performed when the tumor measured approximately 1 cm along its long axis in each group. Further, in an orthotopic tumor model, 40 rats were similarly randomly divided into four groups (n=10 in each group), and intraprostatic injections of 0.05 ml [PBS in group 1,( 165)Ho-chitosan complex solution in group 2, DW-166HC solution (0.5 mCi) in group 3 and DW-166HC solution (1 mCi) in group 4] were performed at 1 week after implantation of the AIT cell line in the ventral prostate. RESULTS: In the subcutaneous tumor model, mean tumor weights of groups 3 and 4 were significantly lower than those of groups 1 and 2 at 2 and 4 weeks post injection (p<0.05). At 2 and 4 weeks after injection in the orthotopic tumor model, the mean weights of the prostate, including tumor, in groups 3 and 4 were also significantly lower than those in groups 1 and 2 (p<0.05). No adverse injury was seen in adjacent organs at histopathologic examination. CONCLUSION: Intratumoral injection of the beta-emitting radionuclide (166)Ho as a form of complex solution with chitosan appears to be a promising alternative therapeutic modality for the local control of prostate cancer.

Our first clinical experience with radiosynoviorthesis by means of (166)Ho-holmium-boro-macroaggregates.

BACKGROUND: In this paper, we evaluate the therapeutic and adverse effects of the application of 166-holmium-boro-macroaggregates (HMBA) in radiosynovectomy (RSO) of the knees. We assessed the efficacy and safety of (166)Ho-HBMA in a prospective clinical trial in patients suffering from chronic synovitis. MATERIAL AND METHODS: An effective component of radiopharmaceutical (166)Ho-boro-macroaggregates is radionuclide (166)Ho which has both beta-emission and gamma-emission. The physical half-life time of 166 Ho is 26.8 hours. After application of the radiopharmaceutical into a joint cavity, the effect of beta-emission causes radiation necrosis of pathologically changed (inflamed) synovial membrane. From 15th April 2005, we have started RSO of knees by means of new radiopharmaceutical (166)Ho-boro-macroaggregates in patients with gonarthrosis, rheumatoid arthritis, chronic synovitis, psoriatic arthritis, gout arthropathy. Seventeen intra-articular injections were performed in fifteen patients receiving a mean activity of 972 MBq (range: 904-1,057 MBq) (166)Ho-HMBA. The patients were hospitalized for three days. Side effects were evaluated during hospital stay and after 6-8 weeks. Static scintigraphy of knee joints and measurements of blood radioactivity were performed. Therapeutic effects were evaluated after 6-8 weeks. RESULTS: In 2 hours and 2 days after application, we proved, by means of knee and inguinal scintigraphy, only insignificant radiopharmaceutical leakage from the joint cavity to the inguinal lymph nodes in four patients. In treated patients, no serious adverse effects occurred. Nine patients were without complaints; 4 patients had slight knee exsudation and 2 patients had great exsudation. Therapeutic effects after 6-8 weeks were as follows: 2 patients were without pain, 9 with lower pain, 3 with the same pain and 1 patient with increased pain. Joint motion was improved in 7 patients, remained the same in 7 patients and was impaired in 1 patient. Analgesics consumption was lower in 5 patients, the same in 9 patients and greater in 1 patient. Knee exsudation was absent in 2 patients, lower in 4 patients, the same in 6 patients and greater in 3 patients. CONCLUSIONS: We proved only insignificant radiopharmaceutical leakage from the joint cavity to the inguinal lymph nodes. Six patients had early slight or great radiation synovitis. The possible cause could be rather high applicated activity. One can take into consideration its reduction. Therapeutic effects can be precisely evaluated after a longer time interval than was possible for us (6-8 weeks after RSO). (166)Ho-boro-macroaggregates can extend the scale of clinically used radiopharmaceuticals for RSO. This paper is presented in the scope of the first stage of clinical evaluation of synovectomy application of holmium-boro-macroaggregates.

Biological comparison of 149Pm-, 166Ho-, and 177Lu-DOTA-biotin pretargeted by CC49 scFv-streptavidin fusion protein in xenograft-bearing nude mice.

The radiolanthanides (149)Pm, (166)Ho, and (177)Lu possess a range of half-lives and alpha(-) beta(-) energies for targeted radiotherapy of cancer. (149)Pm-, (166)Ho-, and (177)Lu-DOTA-biotin were pretargeted to LS174T colorectal tumors in nude mice with CC49 scFvSA antibody-streptavidin fusion protein. Tumor uptakes of (149)Pm (22.9% ID/g), (166)Ho (30.2% ID/g), and (177)Lu (35.4% ID/g) peaked at 1-4 h. Rapid blood disappearance was accompanied by urinary excretion of 59-66% ID within 1 h. Biodistributions of these agents show promise for pretargeted radioimmunotherapy of cancer.

Preparation of Holmium-166 Labelled Macroaggregates for radionuclide synovectomy.

BACKGROUND: Radionuclide synovectomy (radiation synovectomy) is an alternative method that cures patients with rheumatoid arthritis diseases without surgery. During treatment, the suspension of the (166)Ho-macroaggregates radioactive particles ((166)Ho-MA) is administrated via intra-articular injection into the target joint to destroy the inflamed synovium. MATERIAL AND METHODS: The isotope of (166)Ho (E(beta) max = 1.84 MeV, T((1/2)) = 26.8 hr) was prepared by the (165)Ho(n, gamma)(166)Ho reaction in the LWR-15 nuclear reactor (8-10 MW) using approximate neutron flux 10(14) cm-2s-1. RESULTS: The particles of Ho-Macroaggregates with suitable dimension 1-20 microm and the mean diameter of 8.5 microm were prepared. High in-vitro stability was obtained after incubation of neutron-irradiated Ho-Macroaggregates in saline solution (0.9% NaCl). The in-vivo stability on rats was verified as well. CONCLUSIONS: High in-vivo and in-vitro stability as well as supporting gamma radiation of Ho-166 make the Macroaggregates a prospective agent for radionuclide synovectomy. The method of preparation is relatively easy and allows for the production of particles of a suitable dimension with a sufficient amount of radioactivity of Ho-166 for the treatment of the rheumatoid arthritis.