The benefit of bone-seeking radiopharmaceuticals in the treatment of metastatic bone pain

Bisphosphonates as Radiopharmaceuticals: Spotlight on the Development and Clinical Use of DOTAZOL in Diagnostics and Palliative Radionuclide Therapy

Bisphosphonates are therapeutic agents that have been used for almost five decades in the treatment of various bone diseases, such as osteoporosis, Paget disease and prevention of osseous complications in cancer patients. In nuclear medicine, simple bisphosphonates such as 99mTc-radiolabelled oxidronate and medronate remain first-line bone scintigraphic imaging agents for both oncology and non-oncology indications. In line with the growing interest in theranostic molecules, bifunctional bisphosphonates bearing a chelating moiety capable of complexing a variety of radiometals were designed. Among them, DOTA-conjugated zoledronate (DOTAZOL) emerged as an ideal derivative for both PET imaging (when radiolabeled with 68Ga) and management of bone metastases from various types of cancer (when radiolabeled with 177Lu). In this context, this report provides an overview of the main medicinal chemistry aspects concerning bisphosphonates, discussing their roles in molecular oncology imaging and targeted radionuclide therapy with a particular focus on bifunctional bisphosphonates. Particular attention is also paid to the development of DOTAZOL, with emphasis on the radiochemistry and quality control aspects of its preparation, before outlining the preclinical and clinical data obtained so far with this radiopharmaceutical candidate.

DEVELOPMENT AND ESTIMATION OF HUMAN DOSIMETRY OF A NEW 47SC-RISEDRONATE FOR RADIOPHARMACEUTICAL APPLICATION

Bisphosphonate risedronate (2-(3-pyridinyl)-1-hydroxyethane diphosphonic acid) was radiolabeled with scandium-47 (47Sc) as potential therapeutic radiopharmaceutical for skeletal metastases. Its time-dependent biodistribution in mice was measured and its human dosimetry was derived. The labelling process was performed at 95 °C for 30 min. The stability of the radio-conjugate was tested in human serum at 37 °C and its biodistribution was studied in balb/c mice. The radiochemical yield of ≥90% was obtained corresponding to a specific activity of 277 MBq/mg. The radio-conjugate showed good stability in human serum up to 48 h. A high bone uptake by 48 h post-injection was achieved, which suggests that 47Sc-risedronate may be therapeutically beneficial for the palliation of painful bone metastasis. The estimated absorbed dose coefficient and the time-integrated activity coefficient (ã (rs, TD)) in the bone were 1.35 mGy/MBq and 31.04 (Bq-h/Bq), respectively. The absorbed doses to non-osseous normal organs were much lower than that to the bone.

Trends in coordination of rhenium organometallic complexes in the Protein Data Bank

Radiopharmaceutical development has similar overall characteristics to any biomedical drug development requiring a compound's stability, aqueous solubility and selectivity to a specific disease site. However, organometallic complexes containing 188/186Re or 99mTc involve a d-block transition-metal radioactive isotope and therefore bring additional factors such as metal oxidation states, isotope purity and half life into play. This topical review is focused on the development of radiopharmaceuticals containing the radioisotopes of rhenium and technetium and, therefore, on the occurrence of these organometallic complexes in protein structures in the Worldwide Protein Data Bank (wwPDB). The purpose of incorporating the group 7 transition metals of rhenium/technetium in the protein and the reasons for study by protein crystallography are described, as certain PDB studies were not aimed at drug development. Technetium is used as a medical diagnostic agent and involves the 99mTc isotope which decays to release gamma radiation, thereby employed for its use in gamma imaging. Due to the periodic relationship among group 7 transition metals, the coordination chemistry of rhenium is similar (but not identical) to that of technetium. The types of reactions the potential model radiopharmaceutical would prefer to partake in, and by extension knowing which proteins and biomolecules the compound would react with in vivo, are needed. Crystallography studies, both small molecule and macromolecular, are a key aspect in understanding chemical coordination. Analyses of bonding modes, coordination to particular residues and crystallization conditions are presented. In our Forward look as a concluding summary of this topical review, the question we ask is: what is the best way for this field to progress?

Spine and Non-spine Bone Metastases - Current Controversies and Future Direction

Bone is a common site of metastases in advanced cancers. The main symptom is pain, which increases morbidity and reduces quality of life. The treatment of bone metastases needs a multidisciplinary approach, with the main aim of relieving pain and improving quality of life. Apart from systemic anticancer therapy (hormonal therapy, chemotherapy or immunotherapy), there are several therapeutic options available to achieve palliation, including analgesics, surgery, local radiotherapy, bone-seeking radioisotopes and bone-modifying agents. Long-term use of non-steroidal analgesics and opiates is associated with significant side-effects, and tachyphylaxis. Radiotherapy is effective mainly in localised disease sites. Bone-targeting radionuclides are useful in patients with multiple metastatic lesions. Bone-modifying agents are beneficial in reducing skeletal-related events. This overview focuses on the role of surgery, including minimally invasive treatments, conventional radiotherapy in spinal and non-spinal bone metastases, bone-targeting radionuclides and bone-modifying agents in achieving palliation. We present the clinical data and their associated toxicity. Recent advances are also discussed.

ICRP Publication 140: Radiological Protection in Therapy with Radiopharmaceuticals

Radiopharmaceuticals are increasingly used for the treatment of various cancers with novel radionuclides, compounds, tracer molecules, and administration techniques. The goal of radiation therapy, including therapy with radiopharmaceuticals, is to optimise the relationship between tumour control probability and potential complications in normal organs and tissues. Essential to this optimisation is the ability to quantify the radiation doses delivered to both tumours and normal tissues. This publication provides an overview of therapeutic procedures and a framework for calculating radiation doses for various treatment approaches. In radiopharmaceutical therapy, the absorbed dose to an organ or tissue is governed by radiopharmaceutical uptake, retention in and clearance from the various organs and tissues of the body, together with radionuclide physical half-life. Biokinetic parameters are determined by direct measurements made using techniques that vary in complexity. For treatment planning, absorbed dose calculations are usually performed prior to therapy using a trace-labelled diagnostic administration, or retrospective dosimetry may be performed on the basis of the activity already administered following each therapeutic administration. Uncertainty analyses provide additional information about sources of bias and random variation and their magnitudes; these analyses show the reliability and quality of absorbed dose calculations. Effective dose can provide an approximate measure of lifetime risk of detriment attributable to the stochastic effects of radiation exposure, principally cancer, but effective dose does not predict future cancer incidence for an individual and does not apply to short-term deterministic effects associated with radiopharmaceutical therapy. Accident prevention in radiation therapy should be an integral part of the design of facilities, equipment, and administration procedures. Minimisation of staff exposures includes consideration of equipment design, proper shielding and handling of sources, and personal protective equipment and tools, as well as education and training to promote awareness and engagement in radiological protection. The decision to hold or release a patient after radiopharmaceutical therapy should account for potential radiation dose to members of the public and carers that may result from residual radioactivity in the patient. In these situations, specific radiological protection guidance should be provided to patients and carers.

Rhenium-188 Labeled Radiopharmaceuticals: Current Clinical Applications in Oncology and Promising Perspectives

Rhenium-188 (¹⁸⁸Re) is a high energy beta-emitting radioisotope with a short 16.9 h physical half-life, which has been shown to be a very attractive candidate for use in therapeutic nuclear medicine. The high beta emission has an average energy of 784 keV and a maximum energy of 2.12 MeV, sufficient to penetrate and destroy targeted abnormal tissues. In addition, the low-abundant gamma emission of 155 keV (15%) is efficient for imaging and for dosimetric calculations. These key characteristics identify ¹⁸⁸Re as an important therapeutic radioisotope for routine clinical use. Moreover, the highly reproducible on-demand availability of ¹⁸⁸Re from the ¹⁸⁸W/¹⁸⁸Re generator system is an important feature and permits installation in hospital-based or central radiopharmacies for cost-effective availability of no-carrier-added (NCA) ¹⁸⁸Re. Rhenium-188 and technetium-99 m exhibit similar chemical properties and represent a “theranostic pair.” Thus, preparation and targeting of ¹⁸⁸Re agents for therapy is similar to imaging agents prepared with ^99mTc, the most commonly used diagnostic radionuclide. Over the last three decades, radiopharmaceuticals based on ¹⁸⁸Re-labeled small molecules, including peptides, antibodies, Lipiodol and particulates have been reported. The successful application of these ¹⁸⁸Re-labeled therapeutic radiopharmaceuticals has been reported in multiple early phase clinical trials for the management of various primary tumors, bone metastasis, rheumatoid arthritis, and endocoronary interventions. This article reviews the use of ¹⁸⁸Re-radiopharmaceuticals which have been investigated in patients for cancer treatment, demonstrating that ¹⁸⁸Re represents a cost effective alternative for routine clinical use in comparison to more expensive and/or less readily available therapeutic radioisotopes.

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.

Radionuclide Therapy for Bone Metastases: Utility of Scintigraphy and PET Imaging for Treatment Planning

The skeleton is a common site for cancer metastases. Bone metastases are a major cause of morbidity and mortality and associated with pain, pathologic fractures, spinal cord compression, and decreased survival. Various radionuclides have been used for pain therapy. Recently, an α-emitter has been shown to improve overall survival of patients with bone metastases from castration-resistant prostate cancer and was approved as a therapeutic agent. The aim of this article is to provide an overview regarding state of the art radionuclide therapy options for bone metastases, with focus on the role of PET imaging in therapy planning.

188Re-HEDP therapy in the therapy of painful bone metastases

For bone-targeted radionuclide therapy (BTRT), different commercial radiopharmaceuticals are available such as strontium-89, 186Rhenium-hydroxyethylidene diphosphonate (186Re-HEDP), Samarium-153-ethylenediamine tetramethylene phosphonic acid, and radium-223. Unfortunately, the commercial available radiopharmaceuticals are very expensive (from 1,200 to 36,000€ per patient in Europe). The 188W/188Re generator is an ideal source for the long-term (4-6 months) continuous availability of 188Re suitable for the preparation of radiopharmaceuticals for different radionuclide therapies. Labeling at HEDP, it can use cost-effective for BTRT, if enough patients are available for therapy. And so, 188Re-HEDP is the ideal candidate in developing countries which high population to replace the other agents. Two German groups documented a response rate of 80% without any severe side effects and similar bone marrow toxicity compared to the other compounds for 188Re-HEDP. Using 188Re-HEDP in repeated treatments, a prolonged overall survival of repeated to single application was observed (from 4.5 months for single to 15.7 months using ≥≥3 applications).

Preparation and evaluation of rhenium-188-pamidronate as a palliative treatment in bone metastasis

OBJECTIVE

Rhenium-188-hydroxyethylidene diphosphonate (¹⁸⁸Re-HEDP) as a first generation bisphosphonate has been widely used for bone seeking radiopharmaceutical in cases of metastatic bone disease. No study has been yet reported on preparing a complex of ¹⁸⁸Re with pamidronate (3-aminohydroxypropylidene-1,1-bisphosphonic acid) (PMA) as a second generation bisphosphonate. Based on this fact, it was hypothesized that a bone-seeking ¹⁸⁸Re-PMA radiopharmaceutical could be developed as an agent for palliative radiotherapy of bone pain due to skeletal metastases.

METHODS

Pamidronate was labeled with ¹⁸⁸ReO₄^- eluted from the alumina based ¹⁸⁸W/¹⁸⁸Re generator. Labeling was optimized, and radiochemical analysis was performed by thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). Biodistribution of this radioconjugate was evaluated and verified further in mice.

RESULTS

¹⁸⁸Re-PMA was prepared successfully in a high labeling yield (˃95%) corresponding to a specific activity of 124MBq/μmol and good in vitro stability, but it is likely to consist of multiple species. In biodistribution studies selective uptake and retention of activity in the skeletal system (0.81±0.25% ID/g and 0.57±0.16 at 4 and 48h in bone post injection respectively) followed by clearance in the soft tissues were observed.

CONCLUSION

These results show that due to its biological capabilities it would be advantageous to use ¹⁸⁸Re-PMA for bone pain palliation therapy.

Radioisotopes in management of metastatic prostate cancer

INTRODUCTION

Metastatic prostate cancer continues to be a leading cause of morbidity and mortality in men with prostate cancer. Over the last decade, the treatment landscape for patients with castrate-resistant disease has drastically changed, with several novel agents demonstrating an improvement in overall survival in large, multi-institutional randomized trials. Traditional treatment with radioisotopes has largely been in the palliative setting. However, the first in class radiopharmaceutical radium-223 has emerged as the only bone-directed treatment option demonstrating an improvement in overall survival.

METHODS

Medline publications from 1990 to 2016 were searched and reviewed to assess the use of currently approved radioisotopes in the management of prostate cancer including emerging data regarding integration with novel systemic therapies. New positron emission tomography-based radiotracers for advanced molecular imaging of prostate cancer were also queried.

RESULTS

Radioisotopes play a crucial role in the diagnosis and treatment of prostate cancer in the definitive and metastatic setting. Molecular imaging of prostate cancer and theranostics are currently being investigated in the clinical arena.

CONCLUSIONS

The use of modern radioisotopes in selected patients with mCRPC is associated with improvements in overall survival, pain control, and quality of life.

Comparative efficacy, tolerability, and survival outcomes of various radiopharmaceuticals in castration-resistant prostate cancer with bone metastasis: a meta-analysis of randomized controlled trials

Background

A meta-analysis was conducted to assess the impact of radiopharmaceuticals (RPs) in castration-resistant prostate cancer (CRPC) on pain control, symptomatic skeletal events (SSEs), toxicity profile, quality of life (QoL), and overall survival (OS).

Materials and methods

The PubMed/MEDLINE, CANCERLIT, EMBASE, Cochrane Library database, and other search engines were searched to identify randomized controlled trials (RCTs) comparing RPs with control (placebo or radiation therapy) in metastatic CRPC. Data were extracted and assessed for the risk of bias (Cochrane’s risk of bias tool). Pooled data were expressed as odds ratio (OR), with 95% confidence intervals (CIs; Mantel–Haenszel fixed-effects model).

Results

Eight RCTs with a total patient population of 1,877 patients were identified. The use of RP was associated with significant reduction in pain intensity and SSE (OR: 0.63, 95% CI: 0.51–0.78, I²=27%, P,0.0001), improved QoL (OR: 0.71, 95% CI: 0.55–0.91, I²=65%, three trials, 1,178 patients, P=0.006), and a minimal improved OS (OR: 0.84, 95% CI: 0.64–1.04, I²=47%, seven trials, 1,845 patients, P=0.11). A subgroup analysis suggested an improved OS with radium-223 (OR: 0.68, 95% CI: 0.51–0.90, one trial, 921 patients) and strontium-89 (OR: 0.21, 95% CI: 0.05–0.91, one trial, 49 patients). Strontium-89 (five trials) was associated with increased rates of grade 3 and 4 thrombocytopenia (OR: 4.26, 95% CI: 2.22–8.18, P=0.01), leucopenia (OR: 7.98, 95% CI: 1.82–34.95, P=0.02), pain flare (OR: 6.82, 95% CI: 3.42–13.55, P=0.04), and emesis (OR: 3.61, 95% CI: 1.76–7.40, P=0.02).

Conclusion

The use of RPs was associated with significant reduction in SSEs and improved QoL, while the radium-223-related OS benefit warrants further large, RCTs in docetaxel naive metastatic CRPC patients.

Alpha particles induce pan-nuclear phosphorylation of H2AX in primary human lymphocytes mediated through ATM

The use of high linear energy transfer radiations in the form of carbon ions in heavy ion beam lines or alpha particles in new radionuclide treatments has increased substantially over the past decade and will continue to do so due to the favourable dose distributions they can offer versus conventional therapies. Previously it has been shown that exposure to heavy ions induces pan-nuclear phosphorylation of several DNA repair proteins such as H2AX and ATM in vitro. Here we describe similar effects of alpha particles on ex vivo irradiated primary human peripheral blood lymphocytes. Following alpha particle irradiation pan-nuclear phosphorylation of H2AX and ATM, but not DNA-PK and 53BP1, was observed throughout the nucleus. Inhibition of ATM, but not DNA-PK, resulted in the loss of pan-nuclear phosphorylation of H2AX in alpha particle irradiated lymphocytes. Pan-nuclear gamma-H2AX signal was rapidly lost over 24h at a much greater rate than foci loss. Surprisingly, pan-nuclear gamma-H2AX intensity was not dependent on the number of alpha particle induced double strand breaks, rather the number of alpha particles which had traversed the cell nucleus. This distinct fluence dependent damage signature of particle radiation is important in both the fields of radioprotection and clinical oncology in determining radionuclide biological dosimetry and may be indicative of patient response to new radionuclide cancer therapies.

Well-designed bone-seeking radiolabeled compounds for diagnosis and therapy of bone metastases

Bone-seeking radiopharmaceuticals are frequently used as diagnostic agents in nuclear medicine, because they can detect bone disorders before anatomical changes occur. Furthermore, their effectiveness in the palliation of metastatic bone cancer pain has been demonstrated in the clinical setting. With the aim of developing superior bone-seeking radiopharmaceuticals, many compounds have been designed, prepared, and evaluated. Here, several well-designed bone-seeking compounds used for diagnostic and therapeutic use, having the concept of radiometal complexes conjugated to carrier molecules to bone, are reviewed.

Burden of skeletal-related events in prostate cancer: unmet need in pain improvement

PURPOSE

Up to 75% of patients with prostate cancer experience metastatic bone disease, which leads to an increased risk for skeletal-related events (SREs) including pathological bone fracture, spinal cord compression, and hypercalcemia of malignancy. Our objective was to systematically review the literature on the impact of SREs on quality of life (QOL), morbidity, and survival with a primary focus on the impact of SREs on pain in prostate cancer patients.

METHODS

We searched PubMed, limiting to peer-reviewed English-language human studies published in 2000-2010. The search was based on the US Food and Drug Administration and European Medicines Agency definition of an SRE, which includes pathologic fracture, spinal cord compression (SCC), hypercalcemia of malignancy, and radiotherapy or surgery to bone resulting from severe bone pain.

RESULTS

A total of 209 articles were screened, of which 173 were excluded, and 36 were included in this review. Patients with SREs had more pain and worse survival compared with no SREs. Pathologic bone fractures worsened QOL and were associated with shorter survival. Radiation therapy of SCC alleviated pain and improved morbidity. SCC was associated with decreases in patient survival. Radiation therapy and surgery to bone improved pain.

CONCLUSIONS

Specific SREs are associated with worse outcomes, including increased pain, poorer QOL, morbidity, and survival. Treatment of SREs is associated with improved pain, although there remains a need for more effective treatment of SREs in prostate cancer patients.

Pain palliative therapy in women with breast cancer osseous metastatic disease and the role of specific serum cytokines as prognostic factors

PURPOSE

To evaluate the efficacy of radionuclide palliative therapy (RPT) in women suffering from painful metastatic bone disease (MBD) due to breast cancer (BrCa), and to investigate the possible relationship between the RPT efficacy and cytokines levels.

METHODS

Sixty-three BrCa women patients with MBD enrolled in a prospective, nonrandomized study. Thirty were treated with Rhenium-186-hydroxyethylidenediphosphonic acid ((186)Re-HEDP), 21 with Strontium-89-Chloride ((89)Sr-Cl2), and 12 with Samarium-153-thylenediaminetetramethylenephosphonic acid ((153)Sm-EDTMP). Blood samples were collected pre- and post-therapy to assess the interleukin (IL)-2, IL-6 and tumor necrosis factor (TNF)-a titers. The palliative effect of the treatment was evaluated using a modified Wisconsin test.

RESULTS

All three radiopharmaceuticals were equally effective in pain relief. Pain palliation was complete in 52% of patients, partial in 31%, and absent in 16%. Responders to therapy had higher IL-2 and lower IL-6/TNF-a concentrations, compared with nonresponders, even though statistically significant difference in cytokines levels between responders and nonresponders before treatment was noted only for IL-6.

CONCLUSION

All used radiopharmaceuticals had the same therapeutic effect. Pretherapy low titers of IL-6 levels seems to have a favorable prognostic value for the therapeutic outcome, while IL-2 and TNF-a alterations pre- and post-therapy can only serve as markers of a better RPT response.

Beyond Palliation: Therapeutic Applications of 153Samarium-EDTMP

Primary and metastatic malignant bone lesions result in significant pain and disability in oncology patients. Targeted bone-seeking radioisotopes including ¹⁵³Samarium ethylene-diamine-tetramethylene-phosphonic acid (¹⁵³Sm-EDTMP) have been shown to effectively palliate bone pain, often when external beam radiotherapy (EBRT) is not feasible. However, recent evidence also suggests ¹⁵³Sm-EDTMP has cytotoxic activity either alone or in combination with chemotherapy or EBRT. ¹⁵³Sm-EDTMP may be useful as anti-neoplastic therapy apart from pain palliation in a variety of malignancies. For prostate cancer patients, several phase I and II clinical trials have shown that combined ¹⁵³Sm-EDTMP and docetaxel-based chemotherapy can result in >50% decrease in prostate-specific antigen with manageable myelosuppression. In hematologic malignancies, ¹⁵³Sm-EDTMP produced clinical responses when combined with bortezomib in multiple myeloma. ¹⁵³Sm-EDTMP also can be used with myeloablative chemotherapy for marrow conditioning prior to stem cell transplant. In osteosarcoma, ¹⁵³Sm-EDTMP infusion delivers radiation to multiple unresectable lesions simultaneously and provides local cytotoxicity without soft tissue damage that can be combined with chemotherapy or radiation. Prior to routine incorporation of ¹⁵³Sm-EDTMP into therapeutic regimens, we must learn how to ensure optimal delivery to tumors, determine which patients are likely to benefit, improve our ability to assess clinical response in bone lesions and further evaluate the efficacy ¹⁵³Sm-EDTMP in combination with chemotherapy, radiation and novel targeted agents.

Radionuclide therapy of painful bone metastases--a comparative study between consecutive radionuclide infusions, combination with chemotherapy, and radionuclide infusions alone: an in vivo comparison of their effectiveness

Radionuclides have been long used for the palliation of skeletal-related metastatic pain. They are almost invariably used as the last resource for pain palliation. Their use as single agents with dose escalations, in combination with biphosphonates or chemotherapy is well known in the peer-reviewed literature; however, little is known about the combination between different agents. In our study, we used consecutive administration of 2 different radionuclides such as (186)Re-1,1-hydroxyethylidenediphosphonate ((186)Re-HEDP) and (89)Strontium Chloride ((89)Sr-Cl) separated by adequate period of time to allow bone marrow recovery in patients with high chance of bone pain relapse and compared it with (89)Sr-Cl and chemotherapy group and (186)Re-HEDP with bisphosphonates. The end result was that treatment with consecutive radionuclides was much more effective and safe than the other 2 groups.

Bone-targeting radiopharmaceuticals for the treatment of prostate cancer with bone metastases

Patients with castration-resistant prostate cancer (CRPC) frequently have metastases to the bone, which may cause pain and lead to a deterioration in quality-of-life. Bone-seeking radiopharmaceuticals are agents which, when administered systemically, localize to the site of bone metastases and deliver focal radiation there. In this review, we will summarize the current literature on bone-targeting radiopharmaceuticals for CRPC, focusing on strontium-89, samarium-153, rhenium-186 and radium-223. We will discuss their indications, clinical efficacy, and toxicities and highlight some of the challenges in optimizing treatment with these agents. Historically, clinical trials with these drugs have failed to demonstrate survival improvements, restricting their use for palliative purposes only. Radium-223 is the first agent in this class to show an overall survival advantage in CRPC patients with bone metastases. This landmark finding will likely have a considerable impact on the treatment paradigm of bone-metastatic CRPC, and will pave the way for further developments in the future.

Effectiveness of radioisotope therapy in bone metastases, based on personal experience

Aim of the study

Metastatic bone disease is a major clinical and therapeutic problem. It is particularly marked in patients with advanced breast and prostate cancer. Taking into account the diversity of the consequences of skeletal metastases, multidisciplinary patient care should be provided. Among the available treatment methods, radionuclide therapy plays a significant role. The goal of the study was to evaluate and compare the effectiveness of treatment with radionuclides of strontium-89 and samarium-153 in patients with generalized bone metastases.

Material and methods

We analyzed 132 patients with poor pharmacological control of bone pain, caused by multiple metastases due to breast or prostate cancer. In this group of patients radionuclide therapy was administered in the Krakow branch of Oncology Centre between 2002 and 2010.

Results

In the group treated with strontium-89 and samarium-153 total analgesic response rate obtained, was 69% and 83.3%, respectively. In both groups, a significant reduction in analgesics consumption was observed, higher in the group treated with samarium-153. In 14 patients with satisfactory analgesic effect after the first administration of a radioisotope, second administration of radionuclide therapy was attempted at the time of symptoms reappearance. The positive response was achieved in 12 patients. Treatment with both radionuclides was well tolerated.

Conclusions

Radionuclide therapy with strontium-89 and samarium-153 is effective and well tolerated treatment of pain caused by the skeletal metastases. In some cases it is possible to obtain equally good analgesic effect with repeated radioisotopes administration.

Bisphosphonates as radionuclide carriers for imaging or systemic therapy

Bisphosphonates (BP's), biologically stable analogs of naturally occurring pyrophosphates, became the treatment of choice for pathologic conditions characterized by increased osteoclast-mediated bone resorption, namely Paget's disease, osteoporosis and tumor bone disease. Moreover, the clinical success of BP's is also associated with their use in (99m)Tc-based radiopharmaceuticals for bone imaging. In addition to the successful delivery of (99m)Tc (γ-emitter) to bone, BP's have also been used to deliver β(-)-particle emitting radiometals (e.g.(153)Sm, (186/188)Re) for bone-pain palliation. The main goal of this Review is to update the most recent research efforts toward the synthesis, characterization and biological evaluation of novel BP-containing radiometal complexes and radiohalogenated compounds for diagnostic or therapeutic purposes. The structure and in vivo properties of those compounds will be discussed and compared to the clinically available ones, namely in terms of image quality and therapeutic effect. We will also mention briefly the use of BP's as carriers of multimodal nuclear and optical imaging probes.

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.

Biological evaluation of 153Sm and 166Ho complexes with tetraazamacrocycles containing methylcarboxylate and/or methylphosphonate pendant arms

153Sm and 166Ho complexes with two series of tetraazamacrocyclic ligands containing methylcarboxylate and/or methylphosphonate pendant arms were synthesized and their charge, lipophilicity, protein binding and in vitro and in vivo behaviour evaluated. The first series has the same backbone, a 14-membered tetraazamacrocycle containing a pyridine unit with different pendant arms, namely methylcarboxylates (ac3py14) or methylphosphonates (MeP2py14 and P3py14). The second series comprises 12- to 14-membered tetraazamacrocycles having methylcarboxylates and/or methylphosphonates as pendant arms (trans-DO2A2P, TRITA, TRITP, TETA and TETP). The 153Sm/166Ho complexes with the 14-membered tetraazamacrocycles containing the pyridine unit are neutral, hydrophilic, have a significant plasmatic protein binding, are unstable in vivo and present a slow rate of radioactivity excretion and high hepatic retention. 153Sm/166Ho complexes with the 12- to 14-membered tetraazamacrocycles are quantitatively prepared, except those with TETP. These complexes are hydrophilic, have an overall negative charge and present a medium to low plasmatic protein binding.

The 153Sm/166Ho- trans-DO2A2P, 153Sm/166Ho-TRITA and 166Ho-TRITP complexes are stable in vitro and in vivo, presenting a rapid clearance from main organs and a high rate of whole body radioactivity excretion. Biological profile of 153Sm/166Ho-TRITA complexes makes them promising candidates for therapy when conjugated to a biomolecule, while 166Ho-TRITP is potentially useful for bone targeting due to its considerable uptake by bone.

Radiochemical and biological behaviour of 153Sm and 166Ho complexes anchored by a novel bis(methylphosphonate) tetraazamacrocycle

The novel bis(methylphosphonate) 2,2′-[4,10-bis(phosphonomethyl)-1,4,7,10-tetraazacyclododecane-1,7-diyl] diacetic acid, trans-H6DO2A2P, has been synthesized and characterized by multinuclear NMR spectroscopy (1H, 13C and 31P). 153Sm and 166Ho complexes with trans-H6DO2A2P have been prepared in high yield using a 1:2 metal to ligand molar ratio at 70 °C, pH 8−9. These complexes are hydrophilic, negatively charged and stable in vitro under physiological solutions, up to 48 h. They present a low plasmatic protein binding and some in vitro hydroxyapatite adsorption, mainly for 166Ho-trans-DO2A2P. Both complexes are stable in vivo, have a fast tissue clearance from most organs and a rapid total excretion from whole animal body. Moderate bone uptake was also observed but the accumulated radioactivity rapidly decreases with time.

Serum Hemoglobin Levels Predict Response to Strontium-89 and Rhenium-186-HEDP Radionuclide Treatment for Painful Osseous Metastases in Prostate Cancer

OBJECTIVE

Retrospective comparative analysis of strontium-89 chloride (Sr89) and rhenium-186-hydroxyethylidene diphosphonate (Re186-HEDP) radionuclide treatment to find predictors of response in patients with painful metastases from hormone refractory prostate cancer.

PATIENTS AND METHODS

Clinical data from 60 hormone refractory PCA patients (i.e. rising PSA at castrate testosterone serum levels) was obtained. Twenty-nine were treated with Sr89, 31 were treated with Re186-HEDP for painful osseous metastasis. Response was defined as a patient-reported decrease in pain and/or reduction in pain medication with stable pain level. Hematological parameters and serum levels of PSA, alkaline phosphatase, and lactate dehydrogenase were assessed prior to and at 4-week intervals after treatment.

RESULTS

Median survival of all patients was 7 months (95% CI: 6-9 months). Overall, 33/60 (55%) patients reported a decrease in pain after the first radionuclide treatment. This percentage was similar for patients treated with Re168-HEDP and Sr89. Mean duration of reported pain response was 75 days (+/- 68 days) for Sr89 and 61 days (+/- 56 days) for Re186-HEDP, which was not significantly different. A lower blood hemoglobin concentration was associated with a lower pain response rate. In a multivariate Cox regression analysis, pain response to radionuclide treatment predicted longer survival after treatment.

CONCLUSIONS

Pain response was present in 55% of patients. Serum hemoglobin concentration prior to radionuclide treatment predicted pain response for both Re186-HEDP and Sr89. A reduction in pain upon radionuclide treatment was associated with a longer survival after treatment.

Biodistribution of samarium-153-EDTMP in rats treated with docetaxel

PURPOSE: Many patients with metastatic bone disease have to use radiopharmaceuticals associated with chemotherapy to relieve bone pain. The aim of this study was to assess the influence of docetaxel on the biodistribution of samarium-153-EDTMP in bones and other organs of rats. METHODS: Wistar male rats were randomly allocated into 2 groups of 6 rats each. The DS (docetaxel/samarium) group received docetaxel (15 mg/kg) intraperitoneally in two cycles 11 days apart. The S (samarium/control) group rats were not treated with docetaxel. Nine days after chemotherapy, all the rats were injected with 0.1ml of samarium-153-EDTMP via orbital plexus (25µCi). After 2 hours, the animals were killed and samples of the brain, thyroid, lung, heart, stomach, colon, liver, kidney and both femurs were removed. The percentage radioactivity of each sample (% ATI/g) was determined in an automatic gamma-counter (Wizard-1470, Perkin-Elmer, Finland). RESULTS: On the 9th day after the administration of the 2nd chemotherapy cycle, the rats had a significant weight loss (314.50±22.09g) compared (p<0.5) to pre-treatment weight (353.66± 22.8). The % ATI/g in the samples of rats treated with samarium-153-EDTMP had a significant reduction in the right femur, left femur, kidney, liver and lungs of animals treated with docetaxel, compared to the control rats. CONCLUSION: The combination of docetaxel and samarium-153-EDTMP was associated with a lower response rate in the biodistribution of the radiopharmaceutical to targeted tissues. Further investigation into the impact of docetaxel on biodistribution of samarium-153-EDTMP would complement the findings of this study.

Pain therapy

Cancer-related pain is a major issue of healthcare systems worldwide. The reported incidence, considering all stages of the disease, is 51%, which can increase to 74% in the advanced and terminal stages. For advanced cancer, pain is moderate to severe in about 40-50% and very severe or excruciating in 25-30% of cases. Pain is both a sensation and an emotional experience. Pain is always subjective; and may be affected by emotional, social and spiritual components thus it has been defined as "total pain". From a pathophysiological point of view, pain can be classified as nociceptive (somatic and visceral), neuropathic (central, peripheral, sympathetic) idiopathic or psychogenic. A proper pain assessment is fundamental for an effective and individualised treatment. In 1986 the World Health Organisation (WHO) published analgesic guidelines for the treatment of cancer pain based on a three-step ladder and practical recommendations. These guidelines serve as an algorithm for a sequential pharmacological approach to treatment according to the intensity of pain as reported by the patient. The WHO analgesic ladder remains the clinical model for pain therapy. Its clinical application should be employed only after a complete and comprehensive assessment and evaluation based on the needs of each patient. When applying the WHO guidelines, up to 90% of patients can find relief regardless of the settings of care, social and/or cultural environment. This is the standard treatment on a type C basis. Only when such an approach is ineffective are interventions such as spinal administration of opioid analgesics or neuroinvasive procedures recommended.

Role of radiation therapy and radiopharmaceuticals in bone metastases

PURPOSE OF REVIEW

Bone metastases remain the most common cause of cancer-related pain. Palliative radiotherapy and radiopharmaceuticals are effective for symptom control, but continue to be underutilized. We review recent literature for the treatment of bone metastases and spinal cord compression, and address new developments in the prevention of adverse effects secondary to radiotherapy.

RECENT FINDINGS

Evidence continues to mount in support of the efficacy of short-course radiation schedules. Emerging data support the use of single fractions. While radiotherapy is relatively nontoxic, pain flare can be a distressing side effect. Recent reports suggest that traditional and more innovative radiopharmaceuticals are well tolerated, with effects comparable with external beam radiation and the added advantage of addressing multiple, widespread painful sites simultaneously.

SUMMARY

There is an urgent need for more randomized controlled trials in the radiotherapy of complicated bone metastases, such as the settings of spinal cord compression and neuropathic pain. Additional study of radiopharmaceuticals as adjuvants to external beam radiotherapy would also serve to further elucidate the optimal treatment for these patients.

Samarium lexidronam (153Sm-EDTMP): skeletal radiation for osteoblastic bone metastases and osteosarcoma

Radiation therapy can be an effective means to treat bone metastases, which occur in more than 50% of cancer patients. (153)Samarium lexidronam ((153)Sm-EDTMP; Quadramet, Cytogen) is a radiopharmaceutical designed for deposition into bone metastases. Bone scans can identify patients that may benefit from targeted radiation therapy with (153)Sm-EDTMP. As an unsealed source of radiation therapy, (153)Sm-EDTMP is simple to administer: 1 mCi/kg is given in a similar fashion to a bone scan injection ((99m)Tc-MDP bone scan injection is given at 0.2-0.35 mCi/kg. Therefore, both are administered intravenously. However, the radiation-absorbed dose and radiopharmaceutical energy are different). Nevertheless, despite simplicity of administration, (153)Sm-EDTMP is underutilized for improving cancer pain in the skeleton. Repeated cycles and combined treatment with other modalities such as bisphosphonates, chemotherapy and/or external beam radiation are possible. (153)Sm-EDTMP combined with bisphosphonates, chemotherapy and/or radiation may provide better palliation of bone metastases and also in bone-forming tumors (osteosarcoma). Encouraging experience using high-dose (153)Sm-EDTMP for total marrow irradiation in hematologic malignancies involving the bones (e.g., myeloma or acute leukemia) is also reviewed.

A comparative study of 188Re-HEDP, 186Re-HEDP, 153Sm-EDTMP and 89Sr in the treatment of painful skeletal metastases

AIM

The surface bone-seeking radiopharmaceuticals 188Re-HEDP, 186Re-HEDP and 153Sm-EDTMP, and the volume seeker 89Sr were investigated to determine the efficacy and toxicity in pain palliation of bone metastases.

METHOD

The effect of treatment with 188Re-HEDP, 186Re-HEDP, 153Sm-EDTMP and 89Sr on pain symptoms, quality of life, and bone marrow function were studied. In total, 79 patients (18 with breast cancer and 61 with prostate cancer) were treated (31 patients with 188Re-HEDP, 15 patients each with 186Re-HEDP and 153Sm-EDTMP, and 18 patients with 89Sr). All patients were interviewed using standardized sets of questions before and after therapy weekly for 12 weeks. Blood counts were taken weekly for 6 weeks and after 12 weeks.

RESULTS

In total, 73% of patients reported pain relief (77% after 188Re-HEDP, 67% after 186Re-HEDP 73% after 153Sm-EDTMP, and 72% after 89Sr). Fifteen percent of patients could discontinue their analgesics and were pain-free. Pain showed a decrease from 3.6+/-1.7 to a maximum of 2.2+/-1.8 at visual analogue scale in 10 steps (P<0.01). Patients described an improvement on the Karnofsky performance scale from 70+/-10% to 78+/-14% 12 weeks after treatment (P=0.15). There were eight patients with a thrombocytopenia grade I, two patients with grade II and one with grade III. The maximum nadir of platelet and leukocyte counts were observed between the 2nd to 5th week after treatment and was reversible within 12 weeks. There were no significant differences in pain palliation, Karnofsky performance status (KPS) and bone marrow toxicity between the different radionuclides (P=0.087-0.449).

CONCLUSION

All radiopharmaceuticals were effective in pain palliation, without induction of severe side effects or significant differences in therapeutic efficacy or toxicity.

Incident pain and analgesic consumption decrease after samarium infusion: a pilot study

OBJECTIVE

The aim of this pilot study was to observe the variations of pain intensity on movement and at rest and the variation of analgesic drug consumption in patients with prostate cancer and painful bone metastases treated with a single dose of 1.0 mCi/kg of samarium-153 (153-Sm) lexidronam.

DESIGN

Case series.

SETTING

The Nuclear Medicine Unit and Pain Therapy and Palliative Care Unit, National Cancer Institute of Milan, Italy.

PATIENTS

Thirteen outpatients with hormone refractory prostate cancer and painful multiple bone metastases.

INTERVENTIONS

Infusion of a single dose of 1.0 mCi/kg of 153-Sm lexidronam, pain therapy, and the assessment of pain intensity at rest and on movement.

MAIN OUTCOME MEASURES

Variation of pain intensity on movement and at rest by means of a verbal scale and the reduction of analgesic drug consumption 4 weeks after infusion of 153-Sm lexidronam.

RESULTS

From baseline, 61.5% of patients reported a decrease of at least two levels of pain intensity on movement and 53.8% of patients had an improvement of pain at rest. Of the patients, 15.4% were not in pain at rest or on movement at baseline and continued to be free of pain 4 weeks after the administration of samarium. All ten patients, but one, who were on analgesic drugs before samarium infusion, reduced the regular drug administration or rescue medication. Bone marrow toxicity was mild and readily reversible in three patients.

CONCLUSIONS

In patients with bone metastases, pain on movement is a frequent and often difficult clinical problem to treat and the most frequent cause of breakthrough pain. In patients with painful multiple bone metastases due to prostate cancer, the infusion of a single dose of 1.0 mCi/kg of 153-Sm lexidronam may be considered an effective and safe treatment for pain either at rest or during movement.

Samarium for osteoblastic bone metastases and osteosarcoma

Samarium-153 lexidronam (153Sm-EDTMP) is FDA approved for painful osteoblastic bone metastases that image on bone scan. 153Sm-EDTMP decay has a therapeutic beta-emission and a gamma-photon for bone scan imaging. Monitoring of osteosarcoma radiation treatment effectiveness was performed with bone, CT, MRI and PET/CT fusion imaging. Bone scan and PET/CT improved in 5 out of 9 and 16 out of 18 osteosarcoma sites, respectively. 153Sm-EDTMP targets multiple sites of disease, with a single administration. Side effects of 153Sm-EDTMP (0.5-2.5 mCi/kg) have been minimal and include transient thrombocytopenia and neutropenia. 153Sm-EDTMP can be combined with radiation therapy, bisphosphonates and/or chemotherapy to synergistically improve palliation. This article reviews the rationale, indications and monitoring of standard-dose samarium and investigational high-dose 153Sm-EDTMP treatment of cancer involving bone.

Prostate cancer in the elderly

Prostate cancer is the second leading cause of cancer deaths among men. Despite earlier diagnosis due to prostate specific antigen (PSA) screening, it is still a disease of the elderly. Diagnosis is based on digital rectal examination (DRE) and PSA assessment. Refinements in PSA testing (age-specific reference ranges, free PSA, PSA density and velocity) increased specificity and limited unnecessary prostate biopsies. Diagnosis in earlier stages (T1 and T2) commonly leads to cure with current treatment modalities. These include radical prostatectomy, external beam radiotherapy and brachytherapy. Other treatment options under development include cryotherapy and high-intensity focused ultrasound. Metastatic prostate cancer is incurable and treatment is based on hormonal therapy. Cytotoxic chemotherapy has only limited role in hormone-independent prostate cancer. Radioisotopes and biphosphonates may alleviate bone pain and prevent osteoporosis and pathological fractures. Follow-up is based on PSA. Prognostic factors for recurrence include stage, Gleason score, pre- and posttreatment PSA. Quality of life issues play an important role in selecting treatment, especially in the elderly due to comorbidities that may negatively affect the overall quality of life. A holistic approach is recommended addressing all quality of life issues without focus only in cancer control.

Clinical applications of 188Re-labelled radiopharmaceuticals for radionuclide therapy

188Re is a radionuclide in which there is widespread interest for therapeutic purposes because of its favourable physical characteristics. Moreover, it can be eluted from an on-site installable 188W/188Re generator, which has a useful shelf-life of several months. Most of the clinical experiences gained with 188Re concern the use of 188Re-1,1-hydroxyethylidenediphosphonate (188Re-HEDP) for bone pain palliation in patients suffering prostate cancer. The maximum tolerated activity was 3.3 GBq 188Re-HEDP and if the platelet count exceeded 200 x 10(9) l(-1), the administration of 4.4 GBq appeared safe. Evidence for repeated administrations of 188Re-HEDP rather than single injections was established. In general, pain palliation occurs in 60-92% of patients with only moderate transient toxicity, mainly related to changes in blood counts. Also in haematology, radioimmunotherapy by means of 188Re might play a role by selectively targeting the bone marrow in patients undergoing conditioning prior to haematopoetic stem cell transplantation. The feasibility of such an approach was proven using a Re-labelled monoclonal antibody directed toward the CD66-antigen. More recently, encouraging safety data on locoregional treatment of primary liver tumours using 188Re-labelled lipiodol were reported. The normal organs at greatest risk for toxicity are the normal liver and the lungs. About 50% of the patients reported mild and transient side effects, mainly consisting of low grade fever, right hypochondrial discomfort or aggravation of pre-existing liver impairment. Besides the applications in oncology 188Re-based therapies have also been pioneered for benign condition such as prevention of re-stenosis following angioplasty and for radiosynovectomy in cases of refractory arthritis.

Radiation Therapy and Radio-nuclides for Palliation of Bone Pain

Bone pain from metastatic prostate cancer can be effectively palliated by a single fraction of 8 Gy with no increase in toxicity, which can occur with more protracted fractionation schemes. Re-treatment, if required, is simple and effective. For multiple painful sites on the same side of the diaphragm, hemi-body radiotherapy is rapidly effective; pre-medication with odanstetron and steroids has markedly improved tolerance. For multiple painful sites on both sides of the diaphragm, radiopharmaceuticals can be considered but will not treat adjacent soft tissue disease or neurologic compromise.

Systemic radionuclide therapy in pain palliation

Several radiopharmaceuticals were investigated to determine their efficacy and toxicity in the palliation of painful bone metastases. Data on the influence of rhenium-188 hydroxyethylidene diphosphonate (188Re-HEDP), rhenium-186 hydroxyethylidene diphosphonate (186Re-HEDP), and strontium-89 (89Sr) on pain symptoms, quality of life, and bone-marrow function were obtained in 64 patients with breast and prostate cancer. Thirty-one patients were treated with 188Re-HEDP (3194 +/- 387 MBq), 15 patients with 186Re-HEDP (1358 +/- 158 MBq), and 18 patients with 89Sr (152 +/- 19 MBq). The 188Re-HEDP group included six breast cancer patients and 25 prostate cancer patients; the 186Re-HEDP group included three breast cancer patients and 12 prostate cancer patients; and the 89Sr group included three breast cancer patients and 15 prostate cancer patients. All subjects participated in an interview using a standardized sets of questions before and after the 12-week term of therapy. Blood counts were taken weekly for six weeks and after 12 weeks. Results showed that 77 percent of patients reported pain relief after treatment with 188Re-HEDP, 67 percent after treatment with 186Re-HEDP, and 72 percent after treatment with 89Sr. Sixteen percent of patients treated with 188Re-HEDP, 13 percent treated with 186Re-HEDP, and 17 percent treated with 89Sr were able to discontinue their analgesics and were pain-free. Patients described an improvement on Karnofsky performance status (KPS) from 73 +/- 7 percent to 85 +/- 8 percent 12 weeks after 188Re-HEDP (p < 0. 05), from 72 +/- 13 percent to 79 +/- 12 percent after 186Re-HEDP (p = 0.251), and from 62 +/- 14 percent to 69 +/- 16 percent after 89Sr (p = 0.415). Only three patients undergoing 188Re-HEDP therapy, one undergoing 186Re-HEDP therapy, and three undergoing 89Sr therapy had thrombocytopenia (platelet count below 100 x 10(3)/microl) following treatment. The maximum nadir of platelet and leukocyte counts was observed between the second and fifth week after treatment for all radionuclides and was reversible within 12 weeks. The nadir was earlier for 188Re-HEDP with a shorter physical half-life compared with 89Sr. There were no significant differences in bone marrow toxicity (p = 0.123-0.421). Results of this study indicate that all evaluated radiopharmaceuticals were effective in pain palliation without induction of severe side effects. The increase in KPS after 188Re-HEDP was the only statistically significant finding (p = 0.001).

PS-341–mediated selective targeting of multiple myeloma cells by synergistic increase in ionizing radiation-induced apoptosis

OBJECTIVE

Multiple myeloma remains incurable with current therapy. The proteosome inhibitor, PS-341, has shown objective clinical responses in relapsed refractory myeloma patients. We investigated the potential of enhancing the radiosensitivity of myeloma cells by combining with PS-341; the underlying mechanisms were delineated.

MATERIALS AND METHODS

Clonogenic assays were used to evaluate cell survival after exposure to PS-341, ionizing radiation (IR), or PS-341 followed by IR. Apoptosis was studied by annexin V-propidium iodide staining and caspase activation. Cell-cycle phase distribution of cells was determined. Nuclear factor-kappaB (NF-kappaB) activity was monitored by enzyme-linked immunosorbent assay and Western blotting. The expression of death receptor Fas/APO-1/CD95 was analyzed by flow cytometry. The consequential caspase-8 activation was detected by Western blotting.

RESULTS

In clonogenic assays, sequential exposure to nontoxic doses of PS-341 (10 nM) and IR (6 Gy) resulted in synergistic inhibition of proliferation of myeloma cells by modulating the apoptotic sensitivity of these cells. Biochemically, sublethal dose of IR led to potent induction of NF-kappaB activity, and this response was significantly inhibited by pretreatment with PS-341, or by the NF-kappaB inhibitory peptide SN-50. Enhanced Fas expression was seen in myeloma cells exposed sequentially to PS-341 and IR. Finally, PS-341 sensitized primary myeloma (CD138+ve) cells to IR but had little effect on CD138-ve bone marrow cells from myeloma patients.

CONCLUSION

These data indicate that PS-341 can sensitize myeloma cells to IR by both intrinsic and extrinsic apoptotic pathways. The study indicates improved therapeutic benefits in treatment of multiple myeloma by combining PS-341 with conventional radiotherapy.

Management of bone metastases in cancer: a review

The presence of bone metastases is indicative of disseminated disease and typically indicates a short-term prognosis in cancer patients. Palliation of symptoms is the primary goal of therapy, with multidisciplinary efforts yielding the best results. New classes of drugs, such as bisphosphonates that significantly increase the time to first skeletal-related event (SRE), represent useful tools for the treatment of bone metastases. While the optimal duration of therapy needs to be defined, there is clinical benefit derived from the use of this class of agents. A potential role for bisphosphonates in the prevention of bone metastases is under current evaluation in clinical trials encompassing different solid tumor types. In combination with ongoing clinical trials, basic research to identify potential novel targets in the tumor cells-bone microenvironment will further define future strategies in the treatment of bone metastases.