Radiolabeling of zoledronic acid with 188Re as a new palliative agent radiotracer in treatment of bone tumors

Efficacy and Safety of 177Lu-DOTA-IBA in Tumor Bone Metastasis Treatment: A Prospective Clinical Trial

PURPOSE

The aim of this study was to evaluate the efficacy and safety of 177Lu-DOTA-IBA for pain palliation in participants with bone metastases and confirm its potential for treating bone metastasis.

PATIENTS AND METHODS

Overall, 69 participants with bone metastases were included. 68Ga-DOTA-IBA PET/CT was performed within 1 week before treatment. Vital signs, blood markers, electrocardiogram, Karnofsky Performance Status (KPS), and pain scores were evaluated within 7 days before treatment. Postadministration of 177Lu-DOTA-IBA, participants' vital signs and general conditions were monitored. Follow-up evaluations of KPS, pain scores, and blood biomarkers were performed within 8 weeks. 68Ga-DOTA-IBA PET/CT was repeated to evaluate imaging responses at 8 weeks. Imaging responses were defined as complete response, partial response, stable disease, and disease progression. Subsequent treatments were administered based on participants' agreement and clinical conditions.

RESULTS

Sixty-nine participants received at least 1 dose of 177Lu-DOTA-IBA treatment; 22 received 38 reinjected doses, totaling 107 treatments. The median injection dose of 177Lu-DOTA-IBA was 1110 MBq. The pain remission rates after first treatment, retreatment, and total treatment were 82.5%, 72.4%, and 79.3%, respectively. The improvement rates in KPS for first treatment, retreatment, and total treatment were 81.3%, 60.6%, and 74.2%, respectively. The total incidence of the pain flare reaction (temporary aggravation of pain intensity after treatment) was 16.8%. Comparative analysis of 68Ga-DOTA-IBA PET/CT showed a 27.1% rate of partial response imaging response. The total incidence of adverse hematological events was 15%.

CONCLUSIONS

177Lu-DOTA-IBA is a promising bone-seeking radiopharmaceutical with a considerable pain relief rate and safety. It also can benefit some participants with bone metastases in imaging response.

Preparation, Characterization, and Preliminary Imaging Study of [188Re]Re-Ibandronate as a Novel Theranostic Radiopharmaceutical for Bone Metastasis

Background

Bone is a common site of metastasis from a malignant tumor. Several radiopharmaceuticals are available to relieve bone pain in patients with cancer. However, every radiopharmaceutical has its own disadvantages, and there is still a need to investigate easily accessible and high bone affinity radiopharmaceuticals. Ibandronate (IBA) and ¹⁸⁸Re were used for radiolabeling to develop and evaluate a novel type of bone-seeking radiopharmaceutical.

Methods

The preparation conditions of [¹⁸⁸Re]Re-IBA were investigated, and thin-layer chromatography was used to analyze radiochemical purity. The stability, plasma protein binding rate, lipid-water distribution coefficient, safety and biodistribution in normal mice, and bone imaging of [¹⁸⁸Re]Re-IBA in New Zealand rabbits were studied. In addition, the nude mice model of bone metastasis was established, and biodistribution and imaging characteristics of [¹⁸⁸Re]Re-IBA in these nude mice were studied.

Results

[¹⁸⁸Re]Re-IBA was successfully prepared with radiochemical purity >95%. The optimum preparation conditions were as follows: IBA, 0.8–1.4 mg; ascorbic acid, 0.2–0.5 mg; stannous chloride, 0.14–0.18 mg; potassium perrhenate, 0.005 mg; and [¹⁸⁸Re]ReO₄⁻ activity, 18.5–296 MBq, reacted for 30 min at 95°C with pH = 2. [¹⁸⁸Re]Re-IBA demonstrated good stability, high plasma protein binding rate, good hydrophilicity, and low toxicity. The biodistribution and bone imaging in normal animals showed rapid blood clearance, high bone uptake, low uptake in the solid organs and soft tissue, and high contrast during imaging. The biodistribution and imaging of bone metastasis in nude mice showed that [¹⁸⁸Re]Re-IBA has higher uptake in bone metastasis lesions than normal bone.

Conclusions

Our study encompassed the successful preparation of [¹⁸⁸Re]Re-IBA, a novel bone-seeking radiopharmaceutical, and confirmed it has potential in the treatment of bone metastasis and monitoring through imaging.

Dosimetry of bone seeking beta emitters for bone pain palliation metastases

Amongst cancer patients, bone pain due to skeletal metastases is a major cause of morbidity. A number of beta-emitting radiopharmaceuticals have been used to provide internal radiotherapy of bone metastases and provide palliative pain relief. In this article we describe the different physical characteristics of the various beta emitting radionuclides which have been used in this clinical setting and the potential impact of differences in dose-rate on radiobiological outcomes. A detailed review of the biodistribution of these treatments, based on both in-vivo clinical investigations and post mortem autoradiography assessments is provided. These treatments result in physiological delivery of radiation doses to the target disease as well as to critical healthy organs. Particular attention is paid to the radiation doses received by normal bone tissue, bone marrow as well as metastatic bone disease. The underlying models of radiation transport within bone and bone marrow are reviewed alongside the practical steps that must be taken to acquire and analyse the information require for clinical dosimetry assessments. The role of whole body measurements, blood and faecal assays as well as both planar and tomographic gamma camera imaging are considered. In addition we review the rationale for allocating measured bone uptake between trabecular and cortical bone tissue. The difference between bone volume and bone surface seeking radiopharmaceuticals are also discussed. This review also extends to the development of preclinical models of bone metastases which may inform future dosimetric calculations. Finally, we also present a comprehensive review of the dosimetry of the established treatments ⁸⁹Strontium-chloride; ³²Phosphorus; ¹⁸⁸Rhenium-hydroxyethylidine disphosphonate; ¹⁸⁶Rhenium-1,1-hydroxyethylidene disphosphonate (¹⁸⁶Re-HEDP); ¹⁵³Samarium-ethylenediaminetetramethylene phosphonate; as well as the emerging treatments ¹⁸⁸Rhenium-zoledronic acid; ¹⁸⁸Rhenium-ibedronat; ¹⁷⁷Lutetium-zoledronic acid; and ¹⁷⁷Lutetium ethylenediaminetetramethylene phosphonate. This review highlights not only the inter treatment differences in the radiation absorbed doses delivered to metastatic disease by different radiopharmaceuticals but also the intra treatment differences which result in a large range of observed doses between patients.