177Lu-EDTMP: a viable bone pain palliative in skeletal metastasis

Comparison of the relative diagnostic performance of 68Ga-DOTA-IBA and 18F-NaF for the detection of bone metastasis

Purpose

We aimed to compare the relative diagnostic efficacy of 68Ga-Labeled DOTA-ibandronic acid (68Ga-DOTA-IBA) to that of18F-NaF PET/CT as a mean of detecting bone metastases in patients with a range of cancer types.

Methods

This study retrospectively enrolled patients with bone metastases associated with various underlying malignancies. All patients underwent both 68Ga-DOTA-IBA and 18F-NaF PET/CT scans. Histopathology and follow-up CT or MRI imaging results were used as reference criteria, with a minimum follow-up period of 3 months. The maximum Standardized Uptake Value (SUVmax) and number of bone metastases were recorded. The Target-Background Ratio (TBR) was calculated along with the detection rate, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of 68Ga-DOTA-IBA and 18F-NaF PET/CT imaging for overall and partial primary solid tumor bone metastases. Pearson chi-square test, McNemar test, and Kappa test was conducted to assess the correlation and consistency of diagnostic efficiency between the two imaging agents. Receiver Operating Characteristic curve (ROC curve) was performed to compare diagnostic performance and the area under the curve of the two imaging agents, determining optimal critical values for SUVmax and TBR in diagnosing bone metastasis. Differences in SUVmax and TBR values between the two imaging agents for detecting bone metastases were analyzed using the Wilcoxon signed rank test. The difference was statistically significant when P < 0.05.

Results

A total of 24 patients (13 women and 11 men) were included in this study, with a mean age of 52 (interquartile range, 49-64 years). The detection rate, sensitivity, specificity, PPV, NPV, accuracy, and AUC of 68Ga-DOTA-IBA and 18F-NaF PET/CT for bone metastases were 81%, 90%, 62%, 95%, 43%, 88%, 0.763, and 89%, 99%, 59%, 95%, 89%, 95%, 0.789, respectively. There was no significant difference between the two imaging methods (P < 0.01), and there was a significant correlation (X2=168.43, P < 0.001) and a strong consistency (Kappa=0.774,P < 0.001) between the diagnostic results of the two imaging agents. The SUVmax values of lesions measured by 68Ga-DOTA-IBA and 18F-NaF imaging in 22 patients with bone metastasis were 5.1 ± 5.4 and 19.6 ± 15.1, respectively, with statistically significant differences (P<0.05). The TBR values of the two imaging methods were 5.0 ± 5.0 and 6.7 ± 6.4, respectively, with statistically significant differences (P<0.05). The AUC of the SUVmax of 68Ga-DOTA-IBA and 18F-NaF curves were 0.824 and 0.862, respectively, with no statistically significant difference (P=0.490). No significant difference was found in the AUC of the TBR of 68Ga-DOTA-IBA and 18F-NaF (0.832 vs 0.890; P=0.248). Subgroup analysis showed significant correlation between the two imaging agents in the diagnosis of bone metastases in lung cancer and breast cancer, with consistent diagnostic results. However, in the diagnosis of bone metastases in prostate cancer, there was a significant difference (P<0.001) and lack of consistency (P=0.109).

Conclusion

The diagnostic efficacy of 68Ga-DOTA-IBA for bone metastasis lesions is comparable to that of 18F-NaF. This finding holds significant clinical importance in terms of diagnosis of bone metastasis and selecting treatment plans for patients with malignant tumors.

Relaxin inhibits 177Lu-EDTMP associated cell death in osteosarcoma cells through notch-1 pathway

¹⁷⁷Lu-EDTMP (Ethylenediamine tetramethylene phosphonic acid) is the most used radioactive agent for pain palliation in bone cancer patients. The present study aims to study the impact of relaxin-2 on the ¹⁷⁷Lu-EDTMP associated cell toxicity and death in osteosarcoma cells. MG63 and Saos-2 cells were cultured with ¹⁷⁷Lu-EDTMP (37 MBq) for 24 h with and without pretreatment of recombinant relaxin 2 (RLXH2) for 12 and 24 h. ¹⁷⁷Lu-EDTMP associated cellular deterioration and death was determined by LDH, MTT, and trypan blue dye assays. ELISA-based kit was used to determine apoptotic DNA fragmentation. Western blotting was used to determine expression levels of apoptotic-related signalling pathway proteins like bcl2, poly(ADP-ribose) polymerase (PARP), and MAPK (mitogen-activated protein kinase). Our results found that RLXH2 counters ¹⁷⁷Lu-EDTMP associated cellular toxicity. Similarly, RLXH2 was able to counter ¹⁷⁷Lu-EDTMP induced cell death in a concentration and time--dependent manner. Furthermore, it was found that RLXH2 treatment prevents apoptosis in ¹⁷⁷Lu-EDTMP challenged cells through activation of the notch-1 pathway in a concentration- and time-dependent manner. We reported that RLXH2 significantly declined cellular toxicity and apoptosis associated with ¹⁷⁷Lu-EDTMP in MG63 and Saos-2 cells through the notch-1 pathway.

Prospective evaluation of organ-specific dose and lesional doses following therapeutic [177Lu]Lu-EDTMP administration in patients with multiple skeletal metastases and its correlation with clinical hematological toxicity

AIM

In patients with multiple skeletal metastases, accurate estimation of absorbed doses to radiosensitive bone marrow in bone-directed systemic radionuclide therapies (RNT) is critically important from clinical dose determination standpoint. The primary aim of the present study was to estimate the radiation absorbed doses of therapeutic [177Lu]Lu-EDTMP to bone marrow by two methods viz. Medical Internal Radiation Dose (MIRD) schema and using OLINDA software and correlate with hematological toxicity.

METHODS

A total of 15 patients diagnosed to have multiple painful skeletal metastases being treated with [177Lu]Lu-EDTMP for palliation of pain, were enrolled for this prospective study. For all patients, urine was collected immediately after infusion of [177Lu]Lu-EDTMP up to 24 h post-administration and cumulative activity excreted from body via urine was calculated. For dosimetry, patients underwent post-administration whole-body scintigraphy at five-time points: 0.5 (pre-void), 2, 24, 48 and 120 h (post-void). From the time-activity curves generated by drawing regions of interest (ROIs) on the images, number of disintegrations was determined. Absorbed doses for organs and bone lesions were calculated using OLINDA 2.2.0 software. For bone marrow dose estimates, in addition to OLINDA 2.2.0 software, MIRD schema was also adopted. Hematological profile was monitored in all patients during the treatment and post-treatment follow-up (estimating complete blood counts, every 15 d for 3 months after therapy).

RESULTS

The mean ± standard deviation activity of [177Lu]Lu-EDTMP administered per patient per cycle was 2.08 ± 0.45 GBq. The results demonstrated higher uptake of [177Lu]Lu-EDTMP in bone metastases compared to normal bones. Within 2 and 24 h of administration of [177Lu]Lu-EDTMP, [177Lu]Lu activity excreted from the body was 24 ± 9% and 39 ± 14%, respectively. The mean absorbed organ doses (mean ± SD) in Gy/GBq were as follows: osteogenic cells 3.15 ± 1.85, bone marrow 0.57 ± 0.31, kidneys 0.08 ± 0.05, urinary bladder 0.32 ± 0.04, and bone lesions 2.91 ± 1.88. Strong correlation was found between (a) MIRD schema and OLINDA 2.2.0 software method for estimation of bone marrow doses (r = 0.96; P = <0.0001) and (b) Bone marrow absorbed dose and hematological toxicity (r = 0.81, P = 0.0027).

CONCLUSION

Radiation absorbed doses to the bone marrow and skeletal metastatic lesions, following therapeutic [177Lu]Lu-EDTMP were estimated using a convenient and non-invasive quantitative imaging method. The estimated bone marrow absorbed dose, either by MIRD schema or the OLINDA 2.2.0 software method, demonstrated strong correlation. Strong correlation was also observed between bone marrow absorbed dose and hematological toxicity.

An Impressive Approach in Nuclear Medicine: Theranostics

Radiometal-based theranostics or theragnostics, first used in the early 2000s, is the combined application of diagnostic and therapeutic agents that target the same molecule, and represents a considerable advancement in nuclear medicine. One of the promising fields related to theranostics is radioligand therapy. For instance, the concepts of targeting the prostate-specific membrane antigen (PSMA) for imaging and therapy in prostate cancer, or somatostatin receptor targeted imaging and therapy in neuroendocrine tumors (NETs) are part of the field of theranostics. Combining targeted imaging and therapy can improve prognostication, therapeutic decision-making, and monitoring of the therapy.

Progress in Targeted Alpha-Particle-Emitting Radiopharmaceuticals as Treatments for Prostate Cancer Patients with Bone Metastases

Bone metastasis remains a major cause of death in cancer patients, and current therapies for bone metastatic disease are mainly palliative. Bone metastases arise after cancer cells have colonized the bone and co-opted the normal bone remodeling process. In addition to bone-targeted therapies (e.g., bisphosphonate and denosumab), hormone therapy, chemotherapy, external beam radiation therapy, and surgical intervention, attempts have been made to use systemic radiotherapy as a means of delivering cytocidal radiation to every bone metastatic lesion. Initially, several bone-seeking beta-minus-particle-emitting radiopharmaceuticals were incorporated into the treatment for bone metastases, but they failed to extend the overall survival in patients. However, recent clinical trials indicate that radium-223 dichloride (223RaCl2), an alpha-particle-emitting radiopharmaceutical, improves the overall survival of prostate cancer patients with bone metastases. This success has renewed interest in targeted alpha-particle therapy development for visceral and bone metastasis. This review will discuss (i) the biology of bone metastasis, especially focusing on the vicious cycle of bone metastasis, (ii) how bone remodeling has been exploited to administer systemic radiotherapies, and (iii) targeted radiotherapy development and progress in the development of targeted alpha-particle therapy for the treatment of prostate cancer bone metastasis.

Evaluation of Safety and Dosimetry of 177Lu-DOTA-ZOL for Therapy of Bone Metastases

Palliative treatment of bone metastasis using radiolabeled bisphosphonates is a well-known concept proven to be safe and effective. A new therapeutic radiopharmaceutical for bone metastasis is ¹⁷⁷Lu-DOTA-zoledronic acid (¹⁷⁷Lu-DOTA-ZOL). In this study, the safety and dosimetry of a single therapeutic dose of ¹⁷⁷Lu-DOTA-ZOL were evaluated on the basis of a series of SPECT/CT images and blood samples. Methods: Nine patients with exclusive bone metastases from metastatic castration-resistant prostate cancer (mCRPC) (70.8 ± 8.4 y) and progression under conventional therapies participated in this prospective study. After receiving 5,780 ± 329 MBq ¹⁷⁷Lu-DOTA-ZOL, patients underwent 3-dimensional whole-body SPECT/CT imaging and venous blood sampling over 7 d. Dosimetric evaluation was performed for main organs and tumor lesions. Safety was assessed by blood biomarkers. Results: ¹⁷⁷Lu-DOTA-ZOL showed fast uptake and high retention in bone lesions and fast clearance from the bloodstream in all patients. The average retention in tumor lesions was 0.02% injected activity per gram at 6 h after injection and approximately 0.01% at 170 h after injection. In this cohort, the average absorbed doses in bone tumor lesions, kidneys, red bone marrow, and bone surfaces were 4.21, 0.17, 0.36, and 1.19 Gy/GBq, respectively. The red marrow was found to be the dose-limiting organ for all patients. A median maximum tolerated injected activity of 6.0 GBq may exceed the defined threshold of 2 Gy for the red bone marrow in individual patients (4/8). Conclusion: ¹⁷⁷Lu-DOTA-ZOL is safe and has a favorable therapeutic index compared with other radiopharmaceuticals used in the treatment of osteoblastic bone metastases. Personalized dosimetry, however, should be considered to avoid severe hematotoxicity for individual patients.

Targeted Palliative Radionuclide Therapy for Metastatic Bone Pain

Bone metastasis develops in multiple malignancies with a wide range of incidence. The presence of multiple bone metastases, leading to a multitude of complications and poorer prognosis. The corresponding refractory bone pain is still a challenging issue managed through multidisciplinary approaches to enhance the quality of life. Radiopharmaceuticals are mainly used in the latest courses of the disease. Bone-pain palliation with easy-to-administer radionuclides offers advantages, including simultaneous treatment of multiple metastatic foci, the repeatability and also the combination with other therapies. Several β¯- and α-emitters as well as pharmaceuticals, from the very first [⁸⁹Sr]strontium-dichloride to recently introduced [²²³Ra]radium-dichloride, are investigated to identify an optimum agent. In addition, the combination of bone-seeking radiopharmaceuticals with chemotherapy or radiotherapy has been employed to enhance the outcome. Radiopharmaceuticals demonstrate an acceptable response rate in pain relief. Nevertheless, survival benefits have been documented in only a limited number of studies. In this review, we provide an overview of bone-seeking radiopharmaceuticals used for bone-pain palliation, their effectiveness and toxicity, as well as the results of the combination with other therapies. Bone-pain palliation with radiopharmaceuticals has been employed for eight decades. However, there are still new aspects yet to be established.

Leveraging the power of non-radium radionuclide treatments in bone metastases

This review overviews the current status and clinical results of unsealed radionuclide therapies in skeletal metastasis. The other modes of treatment such as external bean radiotherapy and the newer receptor targeted radiopharmaceuticals tagged to alpha and beta particle emitting radionuclides have also been touched upon. With the advent of the latter in recent years, the intravenously administered radiopharmaceuticals that can be employed in the setting of skeletal metastases can be broadly categorized into (i) bone-seeking and (ii) receptor targeted specific tumor-seeking radiopharmaceuticals. The second category conceptualizes the "radionuclide based theranostics" and "precision oncology" and has the additional advantage of targeting both skeletal and non-skeletal disease and being the preferred therapy befitting the contemporary paradigm of clinical oncology.

177Lu/153Sm-Ethylenediamine Tetramethylene Phosphonic Acid Cocktail: A Novel Palliative Treatment for Patients with Bone Metastases

Background: Production of effective, low-cost, and efficient radiopharmaceuticals is an important task and requires further research and clinical studies. In this clinical trial, safety and efficacy of ¹⁷⁷Lu/¹⁵³Sm-ethylenediamine tetramethylene phosphonic acid (EDTMP) cocktail has been evaluated for pain relief of bone metastases. Materials and Methods: Twenty-five patients with the mean age of 55.5 ± 15.8 years participated in this study. Patients received a total dose of 37 MBq/kg. Pain and performance assessments were followed using a Brief Pain Inventory form. Complete blood count and renal and liver function tests were also performed up to 12 weeks postadministration. Results: Eighteen patients (72%) demonstrated complete pain relief (relief = 100%) and approximately all patients (96%) experienced significant improvement in their quality of life. No grade IV hematological toxicity was observed during the 12-week follow-up period, and grade III toxicity was seen in 1 patient only. In addition, no abnormalities were seen in renal and liver function during the follow-up period. Conclusions: There were no considerable complications after administration of ¹⁷⁷Lu/¹⁵³Sm EDTMP; this cocktail seems to be a safe and effective treatment for bone pain palliation in patients with skeletal metastases and improves the quality of life.

Targeted Radionuclide Therapy of Painful Bone Metastases: Past Developments, Current Status, Recent Advances and Future Directions

Bone pain arising from secondary skeletal malignancy constitutes one of the most common types of chronic pain among patients with cancer which can lead to rapid deterioration of the quality of life. Radionuclide therapy using bone-seeking radiopharmaceuticals based on the concept of localization of the agent at bone metastases sites to deliver focal cytotoxic levels of radiation emerged as an effective treatment modality for the palliation of symptomatic bone metastases. Bone-seeking radiopharmaceuticals not only provide palliative benefit but also improve clinical outcomes in terms of overall and progression-free survival. There is a steadily expanding list of therapeutic radionuclides which are used or can potentially be used in either ionic form or in combination with carrier molecules for the management of bone metastases. This article offers a narrative review of the armamentarium of bone-targeting radiopharmaceuticals based on currently approved investigational and potentially useful radionuclides and examines their efficacy for the treatment of painful skeletal metastases. In addition, the article also highlights the processes, opportunities, and challenges involved in the development of bone-seeking radiopharmaceuticals. Radium-223 is the first agent in this class to show an overall survival advantage in Castration-Resistant Prostate Cancer (CRPC) patients with bone metastases. This review summarizes recent advances, current clinical practice using radiopharmaceuticals for bone pain palliation, and the expected future prospects in this field.

Ce-141-labeled DOTMP: A theranostic option in management of pain due to skeletal metastases

Owing to its favorable radioactive decay characteristics (T_1/2  = 32.51 d, E_β [max] = 434.6 keV [70.5%] and 580.0 keV [29.5%], E_γ  = 145.4 keV [48.5%]), ¹⁴¹ Ce could be envisaged as a theranostic radionuclide for use in nuclear medicine. The present article reports synthesis and evaluation of ¹⁴¹ Ce complex of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylenephosphonic acid (DOTMP) as a potent theranostic agent targeting metastatic skeletal lesions. Ce-141 was produced with 314 ± 29 MBq/mg (n = 6) specific activity and >99.9% radionuclidic purity (n = 6). Around 185 MBq dose of [¹⁴¹ Ce]Ce-DOTMP was synthesized with 98.6 ± 0.5% (n = 4) radiochemical yield under optimized conditions of reaction, and the preparation showed adequately high in vitro stability. Biodistribution studies in normal Wistar rats demonstrated significant skeletal localization and retention of injected activity (2.73 ± 0.28% and 2.63 ± 0.22% of injected activity per gram in femur at 3 hours and 14 days post-injection, respectively) with rapid clearance from non-target organs. The results of biodistribution studies were corroborated by serial scintigraphic imaging studies. These results demonstrate the potential utility of ¹⁴¹ Ce-DOTMP as a theranostic molecule for personalized patient care of cancer patients suffering from painful metastatic skeletal lesions.

A "mix-and-use" approach for formulation of human clinical doses of 177 Lu-DOTMP at hospital radiopharmacy for management of pain arising from skeletal metastases

Use of bone-seeking radiopharmaceuticals is an established modality in the palliative care of pain due to skeletal metastases. ¹⁷⁷ Lu-DOTMP is a promising radiopharmaceutical for this application owing to the ideally suited decay properties of ¹⁷⁷ Lu and excellent thermodynamic stability and kinetic rigidity of the macrocyclic complex. The aim of the present study is to develop a robust and easily adaptable protocol for formulation of clinical doses of ¹⁷⁷ Lu-DOTMP at hospital radiopharmacy. After extensive radiochemical studies, an optimized strategy for formulation of clinical doses of ¹⁷⁷ Lu-DOTMP was developed, which involves simple mixing of approximately 3.7 GBq of ¹⁷⁷ Lu activity as ¹⁷⁷ LuCl₃ solution to an aqueous solution containing 5 mg of DOTMP and 8 mg of NaHCO₃ . The proposed protocol yielded ¹⁷⁷ Lu-DOTMP with >98% radiochemical purity, and the resultant formulation showed excellent in vitro stability and desired pharmacokinetic properties in animal model. Preliminary clinical investigations in 5 patients showed specific skeletal accumulation with preferential localization in the osteoblastic lesion sites and almost no uptake in soft tissue or any other major nontarget organ. The developed "mix-and-use" strategy would be useful for large number of nuclear medicine centers having access to ¹⁷⁷ Lu activity and would thereby accelerate the clinical translation of ¹⁷⁷ Lu-DOTMP.

Cocktail Therapy of 177Lu-PSMA-617 and 177Lu-EDTMP in Patients With mCRPC: A Proof-of-Principle Application

Prostate cancer is the second most common primary tumor affecting men worldwide. Among them, 10-20% develop castration resistant prostate cancer (CRPC). Ga-PSMA-PET/CT is an important theranostic agent for the evaluation of CRPC to assess the feasibility of treatment with Lu-PSMA-617 which is a novel therapeutic agent. Interestingly, in certain cases, we have observed non-PSMA-avid lesions despite raised sPSA levels. In this regard, we present a case of cocktail therapy applied using Lu-PSMA-617 and Lu-EDTMP therapy in a 38-year-old male CRPC patient with both soft tissue and extensive skeletal metastases.

Pharmaceutical and clinical development of phosphonate-based radiopharmaceuticals for the targeted treatment of bone metastases

Therapeutic phosphonate-based radiopharmaceuticals radiolabeled with beta, alpha and conversion electron emitting radioisotopes have been investigated for the targeted treatment of painful bone metastases for >35years. We performed a systematic literature search and focused on the pharmaceutical development, preclinical research and early human studies of these radiopharmaceuticals. The characteristics of an ideal bone-targeting therapeutic radiopharmaceutical are presented and compliance with these criteria by the compounds discussed is verified. The importance of both composition and preparation conditions for the stability and biodistribution of several agents is discussed. Very few studies have described the characterization of these products, although knowledge on the molecular structure is important with respect to in vivo behavior. This review discusses a total of 91 phosphonate-based therapeutic radiopharmaceuticals, of which only six agents have progressed to clinical use. Extensive clinical studies have only been described for (186)Re-HEDP, (188)Re-HEDP and (153)Sm-EDTMP. Of these, (153)Sm-EDTMP represents the only compound with worldwide marketing authorization. (177)Lu-EDTMP has recently received approval for clinical use in India. This review illustrates that a thorough understanding of the radiochemistry of these agents is required to design simple and robust preparation and quality control methods, which are needed to fully exploit the potential benefits of these theranostic radiopharmaceuticals. Extensive biodistribution and dosimetry studies are indispensable to provide the portfolios that are required for assessment before human administration is possible. Use of the existing knowledge collected in this review should guide future research efforts and may lead to the approval of new promising agents.

Clinical Efficacy and Safety Comparison of 177Lu-EDTMP with 153Sm-EDTMP on an Equidose Basis in Patients with Painful Skeletal Metastases

This prospective study compared 177Lu-ethylene diamine tetramethylene phosphonate (EDTMP) with 153Sm-EDTMP for painful skeletal metastases.

METHODS

Half of the 32 patients were treated with 177Lu-EDTMP and half with 153Sm-EDTMP, at 37 MBq/kg of body weight. Analgesic, pain, and quality-of-life scores (EORTC, Karnofsky, ECOG) and bone proliferation marker were used to examine efficacy. Hematologic toxicity was evaluated using NCI-CTCAE and compared between groups at baseline and each month till 3 mo after therapy. Pain relief was categorized as complete, partial, minimal, or none.

RESULTS

Pain relief with 177Lu-EDTMP was 80%: 50% complete, 41.67% partial, and 8.33% minimal. Pain relief with 153Sm-EDTMP was 75%: 33.33% complete, 58.33% partial, and 8.33% minimal. The difference was not significant (P=1.000). Quality of life at 3 mo after therapy improved significantly in both groups as per ECOG score (P=0.014 and 0.005 for 177Lu-EDTMP and 153Sm-EDTMP, respectively), Karnofsky index (P=0.007 and 0.023 for 177Lu-EDTMP and 153Sm-EDTMP, respectively), and EORTC score (P=0.004 and <0.001 for 177Lu-EDTMP and 153Sm-EDTMP, respectively). Bone proliferation marker in responders of both groups dropped significantly (P=0.008 for 177Lu-EDTMP and P=0.019 for 153Sm-EDTMP), parallel to clinical response. For 177Lu-EDTMP, anemia, leukopenia, and thrombocytopenia were nonserious (grade I/II) in 46.67%, 46.67%, and 20%, respectively, and serious (grade III/IV) in 20%, 6.67%, and 0%, respectively. For 153Sm-EDTMP, anemia, leukopenia, and thrombocytopenia were nonserious (grade I/II) in 62.5%, 31.25%, and 18.75%, respectively, and serious (grade III/IV) in 18.75%, 0%, and 6.25%, respectively. One patient treated with 153Sm-EDTMP had grade IV thrombocytopenia but required no blood transfusion. Differences between groups were not significant for either nonserious or serious toxicity. For 177Lu-EDTMP, 3 of 12 responders experienced the flare phenomenon on the third day after therapy and one on the fifth day, showing no response to therapy. For 153Sm-EDTMP, 2 of 12 responders experienced the flare phenomenon, both on the third day after therapy.

CONCLUSION

177Lu-EDTMP has pain response efficacy similar to that of 153Sm-EDTMP and is a feasible and safe alternative, especially in centers with no nearby access to 153Sm-EDTMP.

Metastatic Bone Pain Palliation using (177)Lu-Ethylenediaminetetramethylene Phosphonic Acid

¹⁷⁷Lu-ethylenediaminetetramethylene phosphonic acid (EDTMP) is presently suggested as an excellent bone seeking radionuclide for developing metastatic bone pain (MBP) palliation agent owing to its suitable nuclear decay characteristics. To find the exact dosage and its efficiency, this clinical study was performed on the human being, using ¹⁷⁷Lu-EDTMP for MBP palliation. ¹⁷⁷Lu-EDTMP was prepared by Iran, atomic energy organization. Thirty consecutive patients with determined tumors, incontrollable MBP, and positive bone scan at 4 weeks before the beginning of the study participated in this study in the nuclear medicine ward. ¹⁷⁷Lu-EDTMP in the form of sterile slow IV injection was administered with a dose of 29.6 MBq/kg. Short form of brief pain inventory questionnaire was used to evaluate the efficiency of the intervention. Questionnaires were filled out by an expert nuclear physician every 2 weeks while the cell blood count was also checked every 2 weeks up to 12 weeks for evaluation of bone marrow suppression and hematological toxicity. Furthermore, whole body scan was done at days 1, 3, and 7. Twenty-five patients showed a significant pain relief since 2 weeks after the injection, and continued until the end of the follow up period (12 weeks). There were no significant early complications such as bone marrow suppression, hematological toxicity, and no systemic adverse effects. No complication was observed in renal function. Twenty one patients showed flare phenomenon that was started after the 12.2 ± 1.78 h lasting for 38.4 ± 23.08. Sixteen patients (53%) were completely treated; nine patients (30%) showed a partial response, and five patients (17%) had no response to treatment. Total response to treatment was achieved in 25 patients (83%). At the end of the evaluation, no bone marrow suppression or hematologic toxicity was observed. ¹⁷⁷Lu-EDTMP has shown suitable physical and biological properties with good results in long term bone pain relief for patients with bone metastasis.

Production, quality control, biodistribution assessment and preliminary dose evaluation of [177Lu]-tetra phenyl porphyrin complex as a possible therapeutic agent

<p>Due to interesting therapeutic properties of ¹⁷⁷Lu and tumor avidity of tetraphenyl porphyrins (TPPs), ¹⁷⁷Lu-tetraphenyl porphyrin was developed as a possible therapeutic compound. ¹⁷⁷Lu of 2.6-3 GBq/mg specific activity was obtained by irradiation of natural Lu₂O₃sample with thermal neutron flux of 4 × 10¹³ n.cm^-2.s^-1. Tetraphenyl porphyrin was synthetized and labeled with ¹⁷⁷Lu. Radiochemical purity of the complex was studied using Instant thin layer chromatography (ITLC) method. Stability of the complex was checked in final formulation and human serum for 48 h. The biodistribution of the labeled compound in vital organs of wild-type rats was studied up to 7 d. The absorbed dose of each human organ was calculated by medical internal radiation dose (MIRD) method. A detailed comparative pharmacokinetic study was performed for ¹⁷⁷Lu cation and [¹⁷⁷Lu]-TPP. The complex was prepared with a radiochemical purity: >97±1% and specific activity: 970-1000 MBq/mmol. Biodistribution data and dosimetric results showed that all tissues receive approximately an insignificant absorbed dose due to rapid excretion of the complex through the urinary tract. [¹⁷⁷Lu]-TPP can be an interesting tumor targeting agent due to low liver uptake and very low absorbed dose of approximately 0.036 to the total body of human.</p>

Study of Bone Surface Absorbed Dose in Treatment of Bone Metastases via Selected Radiopharmaceuticals: Using MCNP4C Code and Available Experimental Data

Bone metastases are major clinical concern that can cause severe problems for patients. Currently, various beta emitters are used for bone pain palliation. This study, describes the process for absorbed dose prediction of selected bone surface and volume-seeking beta emitter radiopharmaceuticals such as (32)P, (89)SrCl2,(90)Y-EDTMP,(153)Sm-EDTMP, (166)Ho-DOTMP, (177)Lu-EDTMP,(186)Re-HEDP, and (188)Re-HEDP in human bone, using MCNP code. Three coaxial sub-cylinders 5 cm in height and 1.2, 2.6, and 7.6 cm in diameter were used for bone marrow, bone, and muscle simulation respectively. The *F8 tally was employed to calculate absorbed dose in the MCNP4C simulations. Results show that with injection of 1 MBq of these radiopharmaceuticals given to a 70 kg adult man, (32)P, (89)SrCl2, and (90)Y-EDTMP radiopharmaceuticals will have the highest amount of bone surface absorbed dose, where beta particles will have the greatest proportion in absorbed dose of bone surface in comparison with gamma radiation. These results demonstrate moderate agreement with available experimental data.

Production of (177)Lu for Targeted Radionuclide Therapy: Available Options

BACKGROUND

This review provides a comprehensive summary of the production of (177)Lu to meet expected future research and clinical demands. Availability of options represents the cornerstone for sustainable growth for the routine production of adequate activity levels of (177)Lu having the required quality for preparation of a variety of (177)Lu-labeled radiopharmaceuticals. The tremendous prospects associated with production of (177)Lu for use in targeted radionuclide therapy (TRT) dictate that a holistic consideration should evaluate all governing factors that determine its success.

METHODS

While both "direct" and "indirect" reactor production routes offer the possibility for sustainable (177)Lu availability, there are several issues and challenges that must be considered to realize the full potential of these production strategies.

RESULTS

This article presents a mini review on the latest developments, current status, key challenges and possibilities for the near future.

CONCLUSION

A broad understanding and discussion of the issues associated with (177)Lu production and processing approaches would not only ensure sustained growth and future expansion for the availability and use of (177)Lu-labeled radiopharmaceuticals, but also help future developments.

Production, quality control, and bio-distribution studies of (159)Gd-EDTMP as a palliative agent for bone pain

INTRODUCTION

Particle-emitting, bone-seeking radiopharmaceuticals have attracted the attention of the nuclear medicine community over the last three decades for the treatment of the pain of osteoblastic metastases. The objectives of this research were to produce quality-controlled (159)Gd-EDTMP in order to provide a new therapeutic radiopharmaceutical for use in clinical applications.

METHODS

The investigation was an experimental study in which (159)Gd (T1/2=18.479 h, Eβ (max)=970.60 keV, Eγ=363.55 (11.4%) keV] was produced by thermal neutron bombardment of natural Gd2O3 at the Tehran Research Reactor (TRR) for a period of 7 d at a flux of 3-4×10(13) neutrons/cm(2).s. It was then quality-controlled and used to radio-label the in-house prepared ethylene diamine tetra acetic acid (EDTM).

RESULTS

Complexation parameters were optimized to achieve maximum yields (>99%). The radiochemical purity of (159)Gd-EDTMP was checked by radio thin layer chromatography RTLC. It was found to retain its stability at room temperature (>95%). Bio-distribution studies of the complexes conducted in wild rats showed significant bone uptake with rapid clearance from blood.

CONCLUSION

The properties of the (159)Gd-EDTMP that was produced suggest then use of a new, efficient, palliative therapeutic agent for metastatic bone pain instead of some other current radiopharmaceuticals.

(177)Lu-EDTMP for palliation of pain from bone metastases in patients with prostate and breast cancer: a phase II study

PURPOSE

The purpose of this study was to evaluate the efficacy and safety of (177)Lu-EDTMP for pain palliation in patients with bone metastases from castration-resistant prostate and breast cancer. The secondary objective was to compare low-dose and high-dose (177)Lu-EDTMP in bone pain palliation.

METHODS

Included in the study were 44 patients with documented breast carcinoma (12 patients; age 47 ± 13 years) or castration-resistant prostate carcinoma (32 patients; age 66 ± 9 years) and skeletal metastases. Patients were randomized into two equal groups treated with (177)Lu-EDTMP intravenously at a dose of 1,295 MBq (group A) or 2,590 MBq (group B). Pain palliation was evaluated using a visual analogue score (VAS), analgesic score (AS) and Karnofsky performance score (KPS) up to 16 weeks. Toxicity was assessed in terms of haematological and renal parameters.

RESULTS

The overall response rate (in all 44 patients) was 86 %. Complete, partial and minimal responses were seen in 6 patients (13 %), 21 patients (48 %) and 11 patients (25 %), respectively. A favourable response was seen in 27 patients (84 %) with prostate cancer and in 11 patients (92 %) with breast cancer. There was a progressive decrease in the VAS from baseline up to 4 weeks (p < 0.05). Also, AS decreased significantly from 1.8 ± 0.7 to 1.2 ± 0.9 (p < 0.0001). There was an improvement in quality of life of the patients as reflected by an increase in mean KPS from 56 ± 5 to 75 ± 7 (p < 0.0001). The overall response rate in group A was 77 % compared to 95 % in group B (p = 0.188). There was a significant decrease in VAS and AS accompanied by an increase in KPS in both groups. Nonserious haematological toxicity (grade I/II) was observed in 15 patients (34 %) and serious toxicity (grade III/IV) occurred in 10 patients (23 %). There was no statistically significant difference in haematological toxicity between the groups.

CONCLUSION

(177)Lu-EDTMP was found to be a safe and effective radiopharmaceutical for bone pain palliation in patients with metastatic prostate and breast carcinoma. There were no differences in efficacy or toxicity between patients receiving low-dose and high-dose (177)Lu-EDTMP.

Production, quality control and biodistribution studies of thulium-170-labeled ethylenediamine (tetramethylene phosphonic acid)

Thulium-170 (T 1/2 = 128.4 d, E β (max) = 968 keV, E γ = 84 keV (3.26%)) has radionuclidic properties suitable to be used in palliative therapy of bone metastases as an alternative to 89SrCl2. 170Tm can be produced by a relatively easy route involving thermal neutron bombardment on natural Tm2O3 (100% 169Tm) in medium flux research reactors. The requirement for an enriched target does not arise and radionuclidic impurities are not formed by radiative capture during neutron activation. In this study 170Tm was produced using Tm(NO3)3, prepared by neutron activation (3–4E13) of a natural sample. Ethylenediamine (tetramethylene phosphonic acid) (EDTMP) was synthesized and radiolabeled with 170Tm. Complexation parameters were optimized to achieve maximum yields (>99%). The radiochemical purity of 170Tm-EDTMP was checked by RTLC. It was found to retain its stability at room temperature even after 2 months of preparation (> 95%). Biodistribution studies of the complexes carried out in wild-type rats showed significant bone uptake with rapid clearance from blood. The properties of produced 170Tm-EDTMP suggest applying a new efficient bone pain palliative therapeutic agent in the country instead of some other in-use radiopharmaceuticals, such as 89SrCl2 and 32P, in order to overcome metastatic bone pains.

The Role of Bone-Seeking Radionuclides in the Palliative Treatment of Patients with Painful Osteoblastic Skeletal Metastases

Background

Pain from skeletal metastases represents a major burden of advanced disease from solid tumors. Analgesic medications, bisphosphonates, hormonal agents, cytotoxic chemotherapy, and external beam radiotherapy are all effective treatments. However, patients often suffer from diffuse painful metastases and respond poorly to these standard therapies. Bone-seeking radionuclides can specifically target osteoblastic lesions to offer palliation of pain.

Methods

This article offers a narrative review of bone-seeking radionuclides, examines the evidence of safety and efficacy for the treatment of painful skeletal metastases, and presents guidelines for their appropriate use in this patient population.

Results

Seven bone-seeking radionuclides have shown evidence of both safety and efficacy in reducing pain from diffuse skeletal metastases. 153Sm-EDTMP and 89Sr are most commonly used in the United States and have been safely utilized for both repeat dosing as well as concurrent dosing with cytotoxic chemotherapy.

Conclusions

Targeted bone-seeking radionuclides are underutilized in the treatment of painful diffuse osteoblastic metastases. Several new agents are in active clinical investigation, and the pending approval of the first alpha-emitting radionuclide (223Ra) may offer a new class of agents that provide greater efficacy and less toxicity than those currently available for routine clinical use.

An electro-amalgamation approach to produce 175Yb suitable for radiopharmaceutical applications

175Yb is a prospective reactor produced radionuclide suitable for preparation of therapeutic radiopharmaceuticals. However, a major restraint in the use of 175Yb produced via the (n, γ) reaction, for therapeutic applications, is the presence of longer-lived 177Lu impurity which is co-produced along with 175Yb on irradiation of natural Yb2O3 target. A radiochemical separation procedure adopting electro-amalgamation approach for the removal of 177Lu impurity from 175Yb has been critically evaluated. The experimental parameters such as applied potential, electrolysis time and the pH of the electrolyte, affecting the electrochemical separation process, were studied and optimized. The developed radiochemical procedure was extensively tested for purification of up to 15 GBq of 175Yb. The purified 175Yb could be obtained in HCl medium with ∼95% yield. The 177Lu impurity could not be detected in the purified product and 175Yb was found suitable for the preparation of potential radiotherapeutic agents.

Emergence and present status of Lu-177 in targeted radiotherapy: the Indian scenario

177Lu is presently considered to be a potential radionuclide for the development of agents for radionuclide therapy owing to its favorable nuclear decay characteristics [T 1/2 = 6.65 d, E β(max) = 0.497 MeV, E γ = 113 KeV (6.4%) and 208 KeV (11%)]. While the long half-life of this promising radioisotope offers distinct logistic advantage, particularly, in countries having limited reactor facilities, the feasibility of its large-scale production with adequate specific activity and excellent radionuclidic purity in medium flux research reactors constitute yet another desirable feature. Extensive studies have been carried out to optimize the production of this isotope, with high specific activity and radionuclidic purity by the (n,γ) route using the highest available flux and the optimum irradiation time. The gradual evolution of clin ical grade 177LuCl3 as a new radiochemical, ready for commercial deployment by Radiopharmaceuticals Division, Bhabha Atomic Research Centre, to nuclear medicine centers all over India was accomplished in 2010 in a stepwise manner with the commencement of the production of high specific activity 177Lu from enriched target in 2001. Research on 177Lu has demonstrated its immense potential in radiotherapeutic applications, a direct outcome of which has resulted in indigenous development of two agents viz. 177Lu-EDTMP and 177Lu-DOTA-TATE presently being evaluated in human patients for palliative care of bone pain due to skeletal metastases and treatment of malignancies of neuroendocrine origin, respectively. Using locally produced 177Lu, the radiolabeling of a plethora of other molecules with potential applicability in radiation synovectomy and targeted therapy of malignant tumors have been successfully demonstrated. A few of these agent such as a novel 177Lu-labeled porphyrin has shown considerable promise in initial studies and is presently evaluated. In the present article, our research efforts toward standardization of production methodology of 177Lu in high specific activity and its utilization in the devel opment of agents for targeted radiotherapy are being reported.

Multispecies animal investigation on biodistribution, pharmacokinetics and toxicity of 177Lu-EDTMP, a potential bone pain palliation agent

INTRODUCTION

Radionuclide therapy (RNT) is an effective method for bone pain palliation in patients suffering from bone metastasis. Due to the long half-life, easy production and relatively low beta- energy, (177)Lu [T(1/2)=6.73 days, E(beta max)=497 keV, E(gamma)=113 keV (6.4%), 208 keV (11%)]-based radiopharmaceuticals offer logistical advantage for wider use. This paper reports the results of a multispecies biodistribution and toxicity studies of (177)Lu-EDTMP to collect preclinical data for starting human clinical trials.

METHODS

(177)Lu-EDTMP with radiochemical purity greater than 99% was formulated by using a lyophilized kit of EDTMP (35 mg of EDTMP, 5.72 g of CaO and 14.1 mg of NaOH). Biodistribution studies were conducted in mice and rabbits. Small animal imaging was performed using NanoSPECT/CT (Mediso, Ltd., Hungary) and digital autoradiography. Gamma camera imaging was done in rabbits and dogs. Four levels of activity (9.25 through 37 MBq/kg body weight) of (177)Lu-EDTMP were injected in four groups of three dogs each to study the toxicological effects.

RESULTS

(177)Lu-EDTMP accumulated almost exclusively in the skeletal system (peak ca. 41% of the injected activity in bone with terminal elimination half-life of 2130 and 1870 h in mice and rabbits, respectively) with a peak uptake during 1-3 h. Excretion of the radiopharmaceutical was through the urinary system. Imaging studies showed that all species (mouse, rat, rabbit and dog) take up the compound in regions of remodeling bone, while kidney retention is not visible after 1 day postinjection (pi). In dogs, the highest applied activity (37 MBq/kg body weight) led to a moderate decrease in platelet concentration (mean, 160 g/L) at 1 week pi with no toxicity.

CONCLUSION

The protracted effective half-life of (177)Lu-EDTMP in bone supports that modifying the EDTMP molecule by introducing (177)Lu does not alter its biological behaviour as a specific bone-seeking tracer. Species-specific pharmacokinetic behavior differences were observed. Toxicity studies in dogs did not show any biological adverse effects. The studies demonstrate that (177)Lu-EDTMP is a promising radiopharmaceutical that can be further evaluated for establishing as a radiopharmaceutical for human use.