Radiation safety considerations for the use of ²²³RaCl₂ DE in men with castration-resistant prostate cancer

Alpha-Emitting Radionuclides: Current Status and Future Perspectives

The use of radionuclides for targeted endoradiotherapy is a rapidly growing field in oncology. In particular, the focus on the biological effects of different radiation qualities is an important factor in understanding and implementing new therapies. Together with the combined approach of imaging and therapy, therapeutic nuclear medicine has recently made great progress. A particular area of research is the use of alpha-emitting radionuclides, which have unique physical properties associated with outstanding advantages, e.g., for single tumor cell targeting. Here, recent results and open questions regarding the production of alpha-emitting isotopes as well as their chemical combination with carrier molecules and clinical experience from compassionate use reports and clinical trials are discussed.

Radiation protection aspects for alpha therapies

The use of alpha emitting radiotherapeutics is increasing, with further growth expected due to a number of clinical trials currently running involving new alpha emitters. However, literature concerning radiation safety aspects of alpha emitting radionuclides is limited and most of the available literature concerns ²²³Ra. In general, the occupational exposure from alpha emitting radionuclides is expected to be low, as are doses to the public from external exposure. However, care must be taken to avoid skin contamination, inhalation, and ingestion. Not all alpha emitting radionuclides are identical, they often have very different associated decay chains and emissions. The decay chains and the manufacturing process should be carefully examined to identify any long-lived progeny or impurities. These may have an impact on the radiation safety processes required to limit occupational exposure and for waste management. Doses to the public must also be assessed, either arising directly from exposure to patients treated with radiotherapeutics, or via waste streams. Risk assessments should be in place when starting a new service covering all aspects of the preparation and administration, as well as any foreseeable incidents such as skin contamination or patient death, and the appropriate steps to take in these instances. It is imperative that with the increase in the use of alpha emitting radiotherapeutics more literature is published on radiation safety aspects, especially for new alpha emitting radiotherapeutics which often have very different characteristics than the currently established ones.

Radiation safety considerations for the use of radium-224-calciumcarbonate-microparticles in patients with peritoneal metastasis

Aim

Two ongoing phase I studies are investigating the use of radium-224 adsorbed to calcium carbonate micro particles (²²⁴Ra-CaCO₃-MP) to treat peritoneal metastasis originating from colorectal or ovarian cancer. The aim of this work was to study the level of radiation exposure from the patients to workers at the hospital, carers and members of the public.

Method

Six patients from the phase 1 trial in patients with colorectal cancer were included in this study. Two days after cytoreductive surgery, they were injected with 7 MBq of ²²⁴Ra-CaCO₃-MP. At approximately 3, 24 and 120 h after injection, the patients underwent measurements with an ionization chamber and a scintillator-based iodide detector, and whole body gamma camera imaging. The patient was modelled as a planar source to calculate dose rate as a function of distance. Scenarios varying in duration and distance from the patient were created to estimate the potential effective doses from external exposure. Urine and blood samples were collected at approximately 3, 6, 24, 48 and 120 h after injection of ²²⁴Ra-CaCO₃-MP, to estimate the activity concentration of ²²⁴Ra and ²¹²Pb.

Results

The patients' median effective whole-body half-life of ²²⁴Ra-CaCO₃-MP ranged from 2.6 to 3.5 days, with a mean value of 3.0 days. In the scenarios with exposure at the hospital (first 8 days), sporadic patient contact resulted in a range of 3.9-6.8 μSv per patient, and daily contact resulted in 4.3-31.3 μSv depending on the scenario. After discharge from the hospital, at day 8, the highest effective dose was received by those with close daily contact; 18.7-83.0 μSv. The highest activity concentrations of ²²⁴Ra and ²¹²Pb in urine and blood were found within 6 h, with maximum values of 70 Bq/g for ²²⁴Ra and 628 Bq/g for ²¹²Pb.

Conclusion

The number of patients treated with ²²⁴Ra-CaCO₃-MP that a single hospital worker - involved in extensive care - can receive per year, before effective doses of 6 mSv from external exposure is exceeded, is in the order of 200-400. Members of the public and family members are expected to receive well below 0.25 mSv, and therefore, no restrictions to reduce external exposure should be required.

Comparing absorbed doses and radiation risk of the α-emitting bone-seekers [223Ra]RaCl2 and [224Ra]RaCl2

[²²³Ra]RaCl₂ and [²²⁴Ra]RaCl₂ are bone seekers, emitting high LET, and short range (< 100 μm) alpha-particles. Both radionuclides show similar decay properties; the total alpha energies are comparable (²²³Ra: ≈28 MeV, ²²⁴Ra: ≈26 MeV). [²²⁴Ra]RaCl₂ has been used from the mid-1940s until 1990 for treating different bone and joint diseases with activities of up to approximately 50 MBq [²²⁴Ra]RaCl₂. In 2013 [²²³Ra]RaCl₂ obtained marketing authorization by the FDA and by the European Union for the treatment of metastatic prostate cancer with an activity to administer of 0.055 MBq per kg body weight for six cycles. For intravenous injections in humans a model calculation using the biokinetic model of ICRP67 shows a ratio of organ absorbed dose coefficients (²²⁴Ra:²²³Ra) between 0.37 (liver) and 0.97 except for the kidneys (2.27) and blood (1.57). For the red marrow as primary organ-at-risk, the ratio is 0.57. The differences are mainly caused be the differing half-lives of the decay products of both radium isotopes. Both radionuclides show comparable DNA damage patterns in peripheral blood mononuclear cells after internal ex-vivo irradiation. Data on the long-term radiation-associated side effects are only available for treatment with [²²⁴Ra]RaCl₂. Two epidemiological studies followed two patient groups treated with [²²⁴Ra]RaCl₂ for more than 25 years. One of them was the "Spiess study", a cohort of 899 juvenile patients who received several injections of [²²⁴Ra]RaCl₂ with a mean specific activity of 0.66 MBq/kg. Another patient group of ankylosing spondylitis patients was treated with 10 repeated intravenous injections of [²²⁴Ra]RaCl₂, 1 MBq each, 1 week apart. In total 1,471 of these patients were followed-up in the "Wick study". In both studies, an increased cancer mortality by leukemia and solid cancers was observed. Similar considerations on long-term effects likely apply to [²²³Ra]RaCl₂ as well since the biokinetics are similar and the absorbed doses in the same range. However, this increased risk will most likely not be observed due to the much shorter life expectancy of prostate cancer patients treated with [²²³Ra]RaCl₂.

ICRP PUBLICATION 153 Approved by the Commission in September 2022

Veterinary use of radiation in the diagnosis, management, and treatment of disease has expanded and diversified, as have the corresponding radiological protection concerns. Radiological exposure of personnel involved in veterinary procedures and, where applicable, members of the public providing assistance (e.g. owners or handlers) has always been included within the system of radiological protection. Veterinary practice is now addressed explicitly as the modern complexities associated with this practice warrant dedicated consideration, and there is a need to clarify and strengthen the application of radiological protection principles in this area. The Commission recommends that the system of radiological protection should be applied in veterinary practice principally for the protection of humans, but with explicit attention to the protection of exposed animals. Additionally, consideration should be given to the risk of potential contamination of the environment associated with applications of nuclear medicine in veterinary practice. This publication focuses primarily on justification and optimisation in veterinary practice, and sets the scene for more detailed guidance to follow in future Recommendations. It is intended for a wide-ranging audience, including radiological protection professionals, veterinary staff, students, education and training providers, and members of the public, as an introduction to radiological protection in veterinary practice.© 2022 ICRP. Published by SAGE.

Nanomicelles of Radium Dichloride [223Ra]RaCl2 Co-Loaded with Radioactive Gold [198Au]Au Nanoparticles for Targeted Alpha-Beta Radionuclide Therapy of Osteosarcoma

Alpha and beta particulate radiation are used for non-treated neoplasia, due to their ability to reach and remain in tumor sites. Radium-223 (²²³Ra), an alpha emitter, promotes localized cytotoxic effects, while radioactive gold (¹⁹⁸Au), beta-type energy, reduces radiation in the surrounding tissues. Nanotechnology, including several radioactive nanoparticles, can be safely and effectively used in cancer treatment. In this context, this study aims to analyze the antitumoral effects of [²²³Ra]Ra nanomicelles co-loaded with radioactive gold nanoparticles ([¹⁹⁸Au]AuNPs). For this, we synthesize and characterize nanomicelles, as well as analyze some parameters, such as particle size, radioactivity emission, dynamic light scattering, and microscopic atomic force. [²²³Ra]Ra nanomicelles co-loaded with [¹⁹⁸Au]AuNPs, with simultaneous alpha and beta emission, showed no instability, a mean particle size of 296 nm, and a PDI of 0.201 (±0.096). Furthermore, nanomicelles were tested in an in vitro cytotoxicity assay. We observed a significant increase in tumor cell death using combined alpha and beta therapy in the same formulation, compared with these components used alone. Together, these results show, for the first time, an efficient association between alpha and beta therapies, which could become a promising tool in the control of tumor progression.

Cohort profile - MSK radiation workers: a feasibility study to establish a deceased worker sub-cohort as part of a multicenter medical radiation worker component in the million person study of low-dose radiation health effects

BACKGROUND

The National Council on Radiation Protection and Measurements (NCRP) is coordinating an expansive epidemiologic effort entitled the Million Person Study of Low-Dose Radiation Health Effects (MPS). Medical workers constitute the largest occupational radiation-exposed group whose doses are typically received gradually over time.

METHODS

A unique opportunity exists to establish an Institutional Review Board/Privacy Board (IRB/PB) approved, retrospective feasibility sub-cohort of diseased Memorial Sloan Kettering Cancer Center (MSK) medical radiation workers to reconstruct occupational/work history, estimate organ-specific radiation absorbed doses, and review existing publicly available records for mortality from cancer (including leukemia) and other diseases. Special emphasis will be placed on dose reconstruction approaches as a means to provide valid organ dose estimates that are as accurate and precise as possible based on the available data, and to allow proper evaluation of accompanying uncertainties. Such a study that includes validated dose measurements and information on radiation exposure conditions would significantly reduce dose uncertainties and provided greatly improved information on chronic low-dose risks.

RESULTS

The feasibility sub-cohort will include deceased radiation workers from MSK who worked during the nearly seventy-year timeframe from 1946 through 2010 and were provided individual personal radiation dosimetry monitors. A feasibility assessment focused on obtaining records for about 25-30,000 workers, with over 124,000 annual doses, including personnel/work histories, specific dosimetry data, and appropriate information for epidemiologic mortality tracing will be conducted. MSK radiation dosimetry measurements have followed stringent protocols complying with strict worker protection standards in order to provide accurate dose information for radiation workers that include detailed records of work practices (including specific task exposure conditions, radiation type, energy, geometry, personal protective equipment usage, badge position, and missed doses), as well as recorded measurements. These dose measurements have been ascertained through a variety of techniques that have evolved over the years, from film badges to thermoluminescent dosimetry technology to optically stimulated luminescent methodologies. It is expected that individual total doses for the sub-cohort will have a broad range from <10 mSv to > =1000 mSv.

CONCLUSIONS

MSK has pioneered the use of novel radiation diagnostic and therapeutic approaches over time (including initial work with x-rays, radium, and radon), with workplace safety in mind, resulting in a variety of radiation worker exposure scenarios. The results of this feasibility sub-cohort of deceased radiation workers, and associated lessons learned may potentially be applied to an expanded multicenter study of about 170,000 medical radiation worker component of the MPS.

Theragnostic radionuclides: a clinical perspective

The concept of theragnostics goes back to the earliest days of nuclear medicine, with [¹²³I/¹³¹I]iodide in thyroid disease and [¹²³I/¹³¹I]MIBG in phaeochromocytoma being examples in long-term use. However, in recent years there has been a great expansion in the application of theragnostics, beginning with [⁶⁸Ga/¹⁷⁷Lu]-labelled somatostatin peptides for evaluation and treatment of neuroendocrine tumors. We are currently seeing the rapid development of [⁶⁸Ga/¹⁷⁷Lu]PSMA theragnostics in metastatic prostate cancer. While these applications are very promising, there are a number of practicalities which must be addressed in the development and introduction of novel theragnostics. The physical half-lives of the diagnostic and therapeutic radionuclides must be appropriate for imaging and delivery of targeted cell killing, respectively. The types of radioactive emissions are critical; beta particles can traverse several millimeters but also risk damaging non-target tissues, while alpha particles deliver their energy over a much shorter path length, a few cell diameters, and must be more directly targeted. It must be practical to produce the therapeutic radionuclide and the final radiopharmaceutical and deliver them to the final user within an appropriate time-frame determined by half-life and stability. The biodistribution of the agent must demonstrate adequate accumulation and retention in the target tissue with clearance from adjacent and/or radio-sensitive normal tissues. The commercial success of recently introduced theragnostics suggests a rosy future for personalized medicine.

Radiation Safety Considerations and Clinical Advantages of Alpha-Emitting Therapy Radionuclides

Alpha-emitting radionuclides provide an effective means of delivering large radiation doses to targeted treatment locations. Radium-223 dichloride (²²³RaCl₂) is FDA approved for treatment of metastatic castration-resistant prostate cancer (mCRPC) and Actinium-225 (²²⁵Ac-Lintuzumab) radiolabeled antibodies have been shown to be beneficial for patients with acute myeloid leukemia. In recent years, there is an increasing use of alpha emitters in theranostic agents with both small and large molecule constructs. The proper precautionary means for their use and surveying documentation of these isotopes in a clinical setting are an essential accompaniment to these treatments. Methods: Patient treatment data collected over a three-year period, as well as regulatory requirements and safety practices, are described. Commonly used radiation instrumentation was evaluated for their ability to identify potential radioactive material spills and contamination events during a clinical administration of ²²⁵Ac. These instruments were placed at 0.32 cm from a 1.0 cm ²²⁵Ac disk source for measurement purposes. Radiation background values, efficiencies, and minimal detectable activities were measured and calculated for each type of detector. Results: The median external measured patient dose rate from ²²³RaCl₂ patients (n = 611) was 2.5 µSv hr-1 on contact and 0.2 µSv hr-1 at 1 meter immediately after administration. Similarly, ²²⁵Ac-Lintuzumab (n = 19) patients had median external dose rates of 2.0 µSv hr-1 on contact and 0.3 µSv hr-1 at 1 meter. For the measurement of ²²⁵Ac samples, a liquid scintillation counter was found to have the highest overall efficiency (97%), while a zinc sulfide (ZnS) alpha probe offered the lowest minimal detectable activity at 3 counts per minute. Conclusion: In this study, we report data from 630 patients who were undergoing treatment with alpha-emitting isotopes ²²³Ra and ²²⁵Ac. While alpha emitters have ability to deliver higher internal radiation dose to the tissues exposed as compared with other unsealed radionuclides, they typically present minimal external dose rate concerns. Additionally, alpha radiation can be efficiently detected with appropriate radiation instrumentation, such as a liquid scintillation counter or ZnS probe, that should be prioritized when surveying for spills of alpha-emitters.

Radium-223 dichloride causes transient changes in natural killer cell population and cytotoxic function

RATIONALE

Natural killer (NK) cells play an important role in both the innate and adaptive arms of the immune system. While previous studies have demonstrated the effects of ionizing radiation on cytotoxic function of NK cells, little is known about how a chronic exposure to high LET alpha particles emitted by radionuclides will affect both NK population size and function. This study was conducted to determine the effects of ²²³RaCl₂ on splenic NK cell population size and function in Swiss Webster mice.

METHODS

Swiss Webster mice were administered intravenously with 0, 50, or 600 kBq/kg ²²³RaCl₂. Spleens were harvested at 5, 12, and 19 days post-administration. The numbers of splenocytes per spleen were enumerated and flow cytometry was used to assess changes in the distribution of splenocyte subpopulations of B, CD4 and CD8 T lymphocytes, and NK cells. NK functional activity was quantified using YAC-1 target cells and the ⁵¹Cr-release assay.

RESULTS

The total number of splenocytes was unaffected by ²²³RaCl₂. However, significant changes in the distribution of splenocyte subpopulations were observed for NK cells and CD8 T lymphocytes. NK functional activity was enhanced substantially relative to controls at 12 days post-administration, but decreased markedly by day 19.

CONCLUSION

NK functional activity is both diminished and enhanced by ²²³RaCl₂ depending on both administered activity and time post-administration. These results suggest that there may be an optimum window of time to combine the ²²³RaCl₂-induced antitumor NK cell response with other cancer therapies that elicit immune activation.

Intra-articular use of radium dichloride ([223Ra] RaCl2) showed relevant anti-inflammatory response on experimental arthritis model

Rheumatoid arthritis (RA) is an inflammatory chronic autoimmune disease. The treatment of RA is difficult and, in many cases, ineffective, and the arsenal of drugs is limited. Due the longevity of the disease, RA may cause extreme musculoskeletal disorders with a high impact on quality of life. Also, RA is related with severe comorbidities decreasing the life expectancy. Finally, RA has been reported to impact in economy and healthy public. In this direction, the necessity to discover new strategies to efficiently treat RA is immediate. In this direction, we have reported the use of low doses of [²²³Ra] RaCl₂ (radium dichloride) as intra-articular injection to treat RA. Mice were post-treated with [²²³Ra] RaCl₂ (1.48 µCi; i.a.) 24 h after zymosan stimulus. Zymosan-induced arthrithis is responsible for leucocyte recruitment (total leukocytes, neutrophils, and mononuclear cells), which were inhibited by intra-articular injection of [223Ra] RaCl2 (69%, 77%, and 66%, respectively).

In-House Preparation and Quality Control of Ac-225 Prostate-Specific Membrane Antigen-617 for the Targeted Alpha Therapy of Castration-Resistant Prostate Carcinoma

Purpose:

Ac-225 labeled with prostate-specific membrane antigen (PSMA-617), a transmembrane glycoprotein which is highly expressed in prostate carcinoma cells, is presently being considered a promising agent of targeted alpha therapy for the treatment of patients suffering from metastatic castration-resistant prostate cancer. In the present study, we report an optimized protocol for the preparation of therapeutic dose of Ac-225 PSMA-617 with high yield and radiochemical purity (RCP).

Methods:

Ac-225 PSMA-617 was prepared by adding the peptidic precursor-PSMA-617 (molar ratios, Ac-225: PSMA-617 = 30:1) in 1 ml ascorbate buffer to Ac-225 and heating the reaction mixture at 90°C for 25 min to obtain the radiopeptide with high RCP and yield. The radiolabeled peptide was administered in patients who met the eligibility criteria and posttherapy assessment was done.

Results:

Ten batches of Ac-225 PSMA-617 were prepared following this protocol. The radiopeptide was obtained with an adequate yield of 85%–87% and RCP of 97%–99%.

Conclusion:

The current protocol allows single-step, successful, routine inhouse radiolabeling of Ac-225 with PSMA-617 with high yield and RCP.

Radium dial workers: back to the future

PURPOSE

This paper reviews the history of the radium dial workers in the United States, summarizes the scientific progress made since the last evaluation in the early 1990s, and discusses current progress in updating the epidemiologic cohort and applying new dosimetric models for radiation risk assessment.

BACKGROUND

The discoveries of radiation and radioactivity led quickly to medical and commercial applications at the turn of the 20th century, including the development of radioluminescent paint, made by combining radium with phosphorescent material and adhesive. Workers involved with the painting of dials and instruments included painters, handlers, ancillary workers, and chemists who fabricated the paint. Dial painters were primarily women and, prior to the mid to late 1920s, would use their lips to give the brush a fine point, resulting in high intakes of radium. The tragic experience of the dial painters had a significant impact on industrial safety standards, including protection measures taken during the Manhattan Project. The dial workers study has formed the basis for radiation protection standards for intakes of radionuclides by workers and the public.

EPIDEMIOLOGIC APPROACH

The mortality experience of 3,276 radium dial painters and handlers employed between 1913 and 1949 is being determined through 2019. The last epidemiologic follow-up was 30 years ago when most of these workers were still alive. Nearly 65% were born before 1920, 37.5% were teenagers when first hired, and nearly 50% were hired before 1930 when the habit of placing brushes in mouths essentially stopped. Comprehensive dose reconstruction techniques are being applied to estimate organ doses for each worker related to the intake of 226Ra, 228Ra, and associated photon exposures. Time dependent dose-response analyses will estimate lifetime risks for specific causes of death.

DISCUSSION

The study of radium dial workers is part of the Million Person Study of low-dose health effects that is designed to evaluate radiation risks among healthy American workers and veterans. Despite being one of the most important and influential radiation effects studies ever conducted, shifting programmatic responsibilities and declining funding led to the termination of the radium program of studies in the early 1990s. Renewed interest and opportunity have arisen. With scientific progress made in dosimetric methodology and models, the ability to perform a study over the entire life span, and the potential applicability to other scenarios such as medicine, environmental contamination and space exploration, the radium dial workers have once again come to the forefront.

Preclinical and Clinical Status of PSMA-Targeted Alpha Therapy for Metastatic Castration-Resistant Prostate Cancer

Bone, lymph node, and visceral metastases are frequent in castrate-resistant prostate cancer patients. Since such patients have only a few months' survival benefit from standard therapies, there is an urgent need for new personalized therapies. The prostate-specific membrane antigen (PSMA) is overexpressed in prostate cancer and is a molecular target for imaging diagnostics and targeted radionuclide therapy (theragnostics). PSMA-targeted α therapies (PSMA-TAT) may deliver potent and local radiation more selectively to cancer cells than PSMA-targeted β- therapies. In this review, we summarize both the recent preclinical and clinical advances made in the development of PSMA-TAT, as well as the availability of therapeutic α-emitting radionuclides, the development of small molecules and antibodies targeting PSMA. Lastly, we discuss the potentials, limitations, and future perspectives of PSMA-TAT.

Assessment of the radiation exposure of relatives and caregivers of patients treated with Ra-223 - Results of a German multicenter study

A multicenter study was conducted to assess the radiation exposure of relatives and caregivers of patients suffering from castration resistant prostate cancer with bone metastases and treated with Ra-223 dichloride in an outpatient setting. As Ra-223 and most of its progeny emit alpha particles, especially the internal exposure of persons in the patient's vicinity had to be evaluated.

METHODS

The external radiation was measured in distances of 1 m and 2 m. Wipe-tests were taken in the patients' homes to identify significant contaminations and evaluated by liquid scintillation counting. Samples of saliva and sweat were taken and measured using gamma spectrometry.

RESULTS

The external exposure from the patients measured 10-20min post injection (p. i.) was<0.080μSv/h in median in 1 m distance (range: below decision threshold (<DT) - 0.208μSv/h). Ra-223 was found in saliva (median 20-30 min p. i.: 27 Bq/g, range: 12.6 - 110 Bq/g) and excreted with sweat (median: 0.121 Bq/cm², range: 0.020 - 0.524 Bq/cm²) in the first 24h p. i. Contaminations in restrooms and kitchens were low (median: 0.026 - 0.215 mBq/cm², depending on location; range:<DT - 2.1 mBq/cm²).

CONCLUSIONS

The potential exposure of relatives by external irradiation and incorporation of Ra-223 excreted by the patient with saliva or sweat is estimated to be well below 1 mSv. No objections are seen regarding outpatient treatment.

Evolution of radiation protection for medical workers

Within a few months of discovery, X-rays were being used worldwide for diagnosis and within a year or two for therapy. It became clear very quickly that while there were immense benefits, there were significant associated hazards, not only for the patients, but also for the operators of the equipment. Simple radiation protection measures were implemented within a decade or two and radiation protection for physicians and other operators has continued to evolve over the last century driven by cycles of widening uses, new technologies, realization of previously unidentified effects, development of recommendations and regulations, along with the rise of related societies and professional organizations. Today, the continue acceleration of medical radiation uses in diagnostic imaging and in therapeutic modalities not imagined at the turn of this century, such as positron emission tomography, calls for constant vigilance and flexibility to provide adequate protection for the growing numbers of medical radiation workers.

Ra-223 Treatment for Bone Metastases in Castrate-Resistant Prostate Cancer: Practical Management Issues for Patient Selection

Bone metastases are common in men with metastatic castrate-resistant prostate cancer (mCRPC), occurring in 30% of patients within 2 years of castrate resistance and in >90% of patients over the disease course. There are 6 US Food and Drug Administration-approved therapies for mCRPC with demonstrated survival benefit. Of these, only radium-223 (Ra-223) specifically targets bone metastases, delays development of skeletal-related events, and improves survival. This review discusses key data from the ALSYMPCA trial, which contributed to the approval of Ra-223. Data from other trials are highlighted to provide further insight into which patients might benefit from Ra-223. Special patient populations are described, as well as other considerations for the administration of Ra-223. Finally, ongoing trials of Ra-223 combined with other therapies for mCRPC are discussed. These include combining Ra-223 with sipuleucel-T or immunooncology agents, to enhance immune responses, and trials in mildly symptomatic or asymptomatic patients. To date, the optimal timing, sequence, and combinations of Ra-223 with other agents are yet to be determined. The goals of this review are to provide insight into practical aspects of patient selection for Ra-223 treatment and to discuss key therapeutic strategies using the 6 approved mCRPC agents in patients with bone metastases. Results from ongoing trials should help guide the practitioner in using Ra-223 in patients with mCRPC.

Development of Targeted Alpha Particle Therapy for Solid Tumors

Targeted alpha-particle therapy (TAT) aims to selectively deliver radionuclides emitting α-particles (cytotoxic payload) to tumors by chelation to monoclonal antibodies, peptides or small molecules that recognize tumor-associated antigens or cell-surface receptors. Because of the high linear energy transfer (LET) and short range of alpha (α) particles in tissue, cancer cells can be significantly damaged while causing minimal toxicity to surrounding healthy cells. Recent clinical studies have demonstrated the remarkable efficacy of TAT in the treatment of metastatic, castration-resistant prostate cancer. In this comprehensive review, we discuss the current consensus regarding the properties of the α-particle-emitting radionuclides that are potentially relevant for use in the clinic; the TAT-mediated mechanisms responsible for cell death; the different classes of targeting moieties and radiometal chelators available for TAT development; current approaches to calculating radiation dosimetry for TATs; and lead optimization via medicinal chemistry to improve the TAT radiopharmaceutical properties. We have also summarized the use of TATs in pre-clinical and clinical studies to date.

Radiation Exposure to the Nuclear Medicine Personnel During Preparation and Handling of 213Bi-Radiopharmaceuticals

Because of the excellent ability of α-particles to transfer a high amount of energy over a short tissue range, targeted α-therapy has been attracting rising numbers of nuclear medicine centers. In this study, we estimated the radiation exposure to the occupational workers with pocket dosimeters during handling of the α-emitter ²¹³Bi, used for targeted α-therapy of neuroendocrine tumor and castration-resistant prostate cancer patients. The dose rates from patients at different distances and time points after injection of the therapy were also evaluated. Methods: This prospective study was done in the Department of Nuclear Medicine at Fortis Memorial Research Institute, Gurgaon, India. Twelve patients with neuroendocrine tumors or castration-resistant prostate cancer were enrolled to receive ²¹³Bi-DOTATOC or ²¹³Bi-prostate-specific membrane antigen therapy, respectively. Each patient received 2-3 intravenous injections of ²¹³Bi-peptide, 266-362 MBq (7.2-9.8 mCi) in a single cycle over 2-3 d. The radiation exposure to nuclear medicine personnel at the chest and extremity levels was assessed for tasks such as elution, dispensing, injecting, and collecting blood samples. Radiation levels were measured at distances of 1 cm and 1 m from patients immediately after, and at 1, 2, and 4 h after, the administration of ²¹³Bi-peptide. Results: The external dose incurred at the chest level by radiopharmacists during synthesis, by physicians during injection, by technologists during imaging, and by nurses during sample collection was 2-7 μSv/procedure. The extremity dose was 1-14 μSv/procedure. The dose rate at 1 m from patients immediately after ²¹³Bi-radiopharmaceutical injection was 0.02-0.03 μSv/MBq⋅h. Conclusion: The external radiation doses received by occupational workers involved in various procedures were far below the limit prescribed by the regulatory authority (20 mSv/y).

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.

Quantitative measurement of 219Rn radioactivity in exhaled breath from patients with bone metastasis of castration-resistant prostate cancer treated with 223RaCl2

Background

The α-emitting radionuclide radium-223 (²²³Ra) is widely used for the treatment of bone metastasis in patients with castration-resistant prostate cancer. However, ²²³Ra decays into radon-219 (²¹⁹Rn) which is a noble-gas isotope, and ²¹⁹Rn may escape from patients treated with ²²³Ra via their respiration. In this study, we quantified the amount of ²¹⁹Rn contained in the breath of patients treated with ²²³Ra to estimate its effect on the internal exposure dose of caregivers.

Methods

A total of 12 breath samples were collected using a breath collection bag from a total of six patients treated with ²²³RaCl₂. Approximately 300 mL of exhaled breath was collected in a breath bag at 1 min and at 5 min after the start of ²²³RaCl₂ administration. The contents of each bag were measured using an HPGe detector, and the amount of ²¹⁹Rn was quantified based on the detection of the γ peak of ²¹¹Bi, which is a descendant nuclide of ²¹⁹Rn, persisting in the breath bag. The effective dose to caregivers arising from the inhalation of ²¹⁹Rn was estimated by referring to the scenario for the calculation of release criteria established for ¹³¹I therapy in Japan.

Results

A small peak for the 351-keV γ ray of ²¹¹Bi originating from the exhalation of ²¹⁹Rn was observed. Using the observed γ peak of ²¹¹Bi, the average amounts of ²¹⁹Rn per unit breath volume at 1 min and 5 min after the start of ²²³RaCl₂ administration were calculated as 90 ± 56 Bq/mL and 28 ± 9 Bq/mL, respectively. The effective dose of ²¹⁹Rn to caregivers was estimated to be 3.5 μSv per injection.

Conclusions

The amount of ²¹⁹Rn in the exhaled breath of patients treated with ²²³RaCl₂ was quantitatively calculated using breath collection bags. The internal radiation exposure of caregivers from ²¹⁹Rn in the exhaled breath of patients treated with ²²³RaCl₂ is relatively small.

Radium-223 for the treatment of bone metastases in castration-resistant prostate cancer: when and why

Radium-223 dichloride (²²³Ra) is the first, recently approved, α-particle-emitting radiopharmaceutical for the treatment of patients with bone metastases in castration-resistant prostate cancer (CRPC) and no evidence of visceral metastases. We explored MEDLINE, relevant congresses, and websites for data on ²²³Ra and prostate cancer therapies, focusing on therapeutic strategies and timing, bone metastases, and diagnostic assessment. ²²³Ra represents the only bone-targeting agent that has significantly extended patients' overall survival while reducing pain and symptomatic skeletal events. Unlike other radiopharmaceuticals, such as strontium-89 and samarium-153 EDTMP, ²²³Ra (11.4-days half-life) has shown a high biological efficiency mainly due to its short penetration range. These features potentially allow reduced bone marrow toxicity and limit undue exposure. ²²³Ra has been validated under the product name Xofigo^® by the US Food and Drug Administration and the European Medicines Agency. Patient selection, management, and treatment sequencing is recommended to be discussed in the context of a multidisciplinary environment, including oncology, urology, nuclear medicine, and radiation therapy physicians. No consensus has been achieved regarding the optimal timing and its administration as single agent or in combination with zoledronic acid or chemotherapy, so far. This review aims to provide a rationale for the use of ²²³Ra in treating metastases from CRPC, highlighting the crucial role of a multidisciplinary approach, the disputed inclusion and exclusion criteria on the basis of agencies regulations, and the value of diagnostics for therapy assessment.

Potential occupational exposures in diagnostic and interventional radiology: statistical modeling based on Finnish national dose registry data

BACKGROUND

Radiation worker categorization and exposure monitoring practices must be proportional to the current working environment.

PURPOSE

To analyze exposure data of Finnish radiological workers and to estimate the magnitude and frequency of their potential occupational radiation exposure, and to propose appropriate radiation worker categorization.

MATERIAL AND METHODS

Estimates of the probabilities of annual effective doses exceeding certain levels were obtained by calculating the survival function of a lognormal probability density function (PDF) fitted in the measured occupational exposure data.

RESULTS

The estimated probabilities of exceeding annual effective dose limits of 1 mSv, 6 mSv, and 20 mSv were in the order of 1:200, 1:10,000, and 1:500,000 per person, respectively.

CONCLUSION

It is very unlikely that the Category B annual effective dose limit of 6 mSv could even potentially be exceeded using modern equipment and appropriate working methods. Therefore, in terms of estimated effective dose, workers in diagnostic and interventional radiology could be placed into Category B in Finland. Current national personal monitoring practice could be replaced or supplemented using active personal dosimeters, which offer more effective means for optimizing working methods.

RECOMMENDATIONS FOR MONITORING AND INTERNAL DOSIMETRY FOR NUCLEAR MEDICINE STAFF EXPOSED TO RADIOPHARMACEUTICALS 223Ra DICHLORIDE

223Ra is a radiopharmaceutical used as unsealed source in nuclear medicine. In the case of staff inhalation contamination of 223Ra, methods to estimate the committed effective dose should be chosen with care. Three methods are available: whole-body measurement and gamma spectrometry for urine or faeces samples. Considering the analytical performances and uncertainties of these three methods, we propose recommendations for special dose assessment. As a first choice, due to its rapidity and its non-invasiveness, an in vivo analysis (with HPGe detector) is the most appropriate method. However, after 24 h, whole-body counting is not sensitive enough to detect a minimum effective dose of 1 mSv. Sufficient sensitivity can only be reached up to 8 days after contamination by true 24 h faeces samples analyses. Thus, despite its main drawbacks, this method appears to be more appropriate than urine to estimate the committed effective dose in addition to whole-body counting.

Treatment of Bone Metastasis with Bone-Targeting Radiopharmaceuticals

Bone is a common metastatic site of cancer. Bone metastasis reduces life expectancy and results in serious symptoms and complications such as bone pain, pathological fractures, and spinal cord compression, decreasing quality of life by restricting sleep and mobility. Treatment for bone metastasis includes drugs (pure analgesics, hormones, cytotoxic chemotherapy, and bisphosphonates, among others), external radiation therapy, surgery, and radionuclide therapy using bone-targeting radiopharmaceuticals. Particulate radiation with α- or β-rays is used as a bone-targeting radiopharmaceutical in radionuclide therapy. β-Emitters have lower energy and a longer range than α-emitters and have less tumoricidal activity and deliver more radiation to adjacent normal tissue. Therefore, the main therapeutic effect of bone-targeting β-emitters such as 89Sr-dichloride is bone pain palliation rather than enhanced survival. In contrast, α-emitters such as 223Ra-dichloride have high energy and a short range, resulting in greater tumoricidal activity and less radiation damage to adjacent normal tissue. Treatment with bone-targeting α-emitters can improve survival and decrease bone pain. This review focuses on the principles and clinical utility of several clinically available bone-targeting radiopharmaceuticals in metastatic bone disease.

Comparison of day 3 and day 5 thyroglobulin results after thyrogen injection in differentiated thyroid cancer patients

BACKGROUND

It is necessary to stimulate serum thyroid-stimulating hormone (TSH) levels either endogenously by thyroid hormone withdrawal (THW) or exogenously by administration of recombinant human TSH (rhTSH) for radioactive iodine (RAI) therapy. Thyrotropin alfa (Thyrogen) has many advantages over THW. Radiation dose to laboratory staff while drawing blood for tests on the day 5 is one of the disadvantages of preferring Thyrogen. Our aim was to compare day 3 and day 5 blood test results after Thyrogen injections.

MATERIAL AND METHOD

In our study, Thyrogen was preferred in 32 differentiated thyroid cancer patients with a mean age of 50.5 ± 12.3 years. Thyrogen was injected on day 1 and day 2 intramuscularly in all patients before I-131 was given on day 3. A total of 22 patients received 5 mCi RAI for ablation control scintigraphy and 10 patients received 100-250 mCi RAI for ablation or therapy (high-dose group). Blood tests were performed on day 3 and day 5 after Thyrogen injections.

RESULTS

Mean TSH level was 98.1 mg/dl for day 3 and 29.5 mg/dl for day 5. In the diagnostic group, thyroglobulin (Tg) and anti-Tg levels were nearly the same on day 3 and day 5. In the therapy group, day 5 Tg levels were higher than day 3.

CONCLUSION

After Thyrogen injection of two consecutive days, blood sampling might be enough on day 3. Day 5 blood sampling may not be necessary routinely for radiation protection of laboratory staff. For the diagnostic group, if Tg and anti-Tg is normal then 5 mCi imaging may not be necessary.

Targeted alpha-particle therapy: imaging, dosimetry, and radiation protection

Systemic or locoregionally administered alpha-particle emitters are highly potent therapeutic agents used in oncology that are fundamentally novel in their mechanism and, most likely, overcome radiation resistance as the alpha particles emitted have a short range and a high linear energy transfer. The use of alpha emitters in a clinic environment requires extra measures with respect to imaging, dosimetry, and radiation protection. This is shown for the example of ²²³Ra dichloride therapy. After intravenous injection, ²²³Ra leaves the blood and is taken up rapidly in bone and bone metastases; it is mainly excreted via the intestinal tract. ²²³Ra can be imaged in patients with a gamma camera. Dosimetry shows that, after a series of six treatments for a 70-kg person with an overall administered activity of 23 MBq, ²²³Ra results in an absorbed alpha dose of approximately 17 Gy to the bone endosteum and approximately 1.7 Gy to the red bone marrow. During administration, special care must be taken to ensure that no spill is present on the skin of either the patient or staff. Due to the low dose rate, the treatment is normally performed on an outpatient basis; the patient and carers should receive written instructions about the therapy and radiation protection.

α-Emitters for Radiotherapy: From Basic Radiochemistry to Clinical Studies-Part 1

With a short particle range and high linear energy transfer, α-emitting radionuclides demonstrate high cell-killing efficiencies. Even with the existence of numerous radionuclides that decay by α-particle emission, only a few of these can reasonably be exploited for therapeutic purposes. Factors including radioisotope availability and physical characteristics (e.g., half-life) can limit their widespread dissemination. The first part of this review will explore the diversity, basic radiochemistry, restrictions, and hurdles of α-emitters.

Excretion and whole-body retention of radium-223 dichloride administered for the treatment of bone metastases from castration resistant prostate cancer

OBJECTIVE

The aim of the study was to determine the fraction of administered activity that was excreted and retained by a small cohort of patients who each received treatment with radium-223 dichloride (Ra). Ra is an α-emitting radionuclide that has been approved for use in the treatment of bone metastases that are secondary to castration resistant prostate cancer.

PATIENTS AND METHODS

Six patients received two weight-based administrations of Ra 6 weeks apart. Activity excreted in the urine and faeces during the first 48 h following each treatment was assessed by direct counting of the excreta. During the same period the whole-body retention of Ra was also determined using a single probe counting system. The results of the excreta counting and the whole-body counting were compared to determine whether whole-body counting was a suitable surrogate for assessing excretion. Further whole-body retention counts were made at around 3, 4, 7 and 42 days following treatment.

RESULTS

Patterns of excretion and retention of Ra varied significantly between patients, but were similar for each patient's pair of treatments. The cumulative maximum activity excreted in the initial 8-h period following the Ra administration was 2.6% that increased to 39% at 48 h. The median excreted activity at ~1 and 6 weeks after treatment was 70 and 86%, respectively. Skeletal retention of Ra at 6 weeks ranged from 11 to 60% of the administered activity.

EANM guideline for radionuclide therapy with radium-223 of metastatic castration-resistant prostate cancer

Radium Ra-223 dichloride (radium-223, Xofigo®) is a targeted alpha therapy approved for the treatment of castration-resistant prostate cancer (CRPC) with symptomatic bone metastases and no known visceral metastatic disease. Radium-223 is the first targeted alpha therapy in this indication providing a new treatment option, with evidence of a significant survival benefit, both in overall survival and in the time to the first symptomatic skeletal-related event. The skeleton is the most common metastatic site in patients with advanced prostate cancer. Bone metastases are a clinically significant cause of morbidity and mortality, often resulting in bone pain, pathologic fracture, or spinal cord compression necessitating treatment. Radium-223 is selectively accumulated in the bone, specifically in areas of high bone turnover, by forming complexes with the mineral hydroxyapatite (the inorganic matrix of the bone). The alpha radiation generated during the radioactive decay of radium-223 produces a palliative anti-tumour effect on the bone metastases. The purpose of this guideline is to assist nuclear medicine specialists in evaluating patients who might be candidates for treatment using radium-223, planning and performing this treatment, understanding and evaluating its consequences, and improving patient management during therapy and follow-up.

Radium 223 dichloride for prostate cancer treatment

Prostate cancer is the most common malignant disease in men. Several therapeutic agents have been approved during the last 10 years. Among them, radium-223 dichloride (Xofigo^®) is a radioactive isotope that induces irreversible DNA double-strand breaks and consequently tumor cell death. Radium-223 dichloride is a calcium-mimetic agent that specifically targets bone lesions. Radium-223 dichloride has been approved for the treatment of metastatic castration-resistant prostate cancer with symptomatic bone metastases, without known visceral metastases. In this review, first we summarize the interplay between prostate tumor cells and bone microenvironment; then, we discuss radium-223 dichloride mechanism of action and present the results of the available clinical trials and future developments for this new drug.

Targeted Radionuclide Therapy: An Evolution Toward Precision Cancer Treatment

OBJECTIVE

This article reviews recent developments in targeted radionuclide therapy (TRT) approaches directed to malignant liver lesions, bone metastases, neuroendocrine tumors, and castrate-resistant metastatic prostate cancer and discusses challenges and opportunities in this field.

CONCLUSION

TRT has been employed since the first radioiodine thyroid treatment almost 75 years ago. Progress in the understanding of the complex underlying biology of cancer and advances in radiochemistry science, multimodal imaging techniques including the concept of "see and treat" within the framework of theranostics, and universal traction with the notion of precision medicine have all contributed to a resurgence of TRT.

Bone-Targeted Imaging and Radionuclide Therapy in Prostate Cancer

Although selective metabolic and receptor-based molecular agents will surely be included in the future of prostate cancer diagnosis and therapy, currently available inorganic compounds-such as ¹⁸F-NaF for the diagnosis of bony disease and ²²³RaCl₂ for the therapy of bone metastases-were recently shown to be superior to standard ^99mTc-phosphonates for diagnosis and ¹⁵³Sm-ethylenediaminetetramethylene phosphonate or ⁸⁹SrCl₂ for therapy. The advantages of ¹⁸F-NaF include improved lesion detection and, when used in combination with CT, improved diagnostic confidence and specificity. In addition to being the first approved α-emitter, ²²³RaCl₂ is the first radiopharmaceutical to show an increase in overall survival, a decrease in skeletal events, palliation of bone pain, and a low profile of adverse reactions (which are mild and manageable). The management of metastatic bone disease with ²²³RaCl₂ is uniquely satisfying, as patients can be monitored directly during their monthly treatment visits.

Management of metastatic castration-resistant prostate cancer: A focus on radium-223: Opinions and suggestions from an expert multidisciplinary panel

Radium-223, a calcium mimetic bone-seeking radionuclide that selectively targets bone metastases with alpha particles, is approved for the treatment of men with metastatic castration-resistant prostate cancer (mCRPC) and symptomatic bone metastases. In patients with mCRPC, treatment with radium-223 has been associated with survival benefit, regardless of prior docetaxel use, and also has a positive impact on symptomatic skeletal events and quality of life. Radium-223 is best suited for patients with symptomatic mCRPC and bone-predominant disease and no visceral metastases, and may lead to better outcomes when given early in the course of the disease. An expert multidisciplinary panel convened in Milan, Italy to review the current best-evidence literature on radium-223 and to convey their personal expertise with the use of radium-223 and identify possible strategies for best practice. This article summarizes the best available evidence for the use of radium-223, discusses the essential role of the multidisciplinary team in delivering effective treatment for mCRPC, clarifies pre- and post-treatment evaluation and monitoring, and outlines future scenarios for radium-223 in the treatment of men with MCRPC.

Radionuclides in oncology clinical practice – review of the literature

Radionuclide therapy is a promising type of targeted therapy for cancer and its use is becoming more common in several types of malignant tumors.

Sipuleucel-T and Androgen Receptor-Directed Therapy for Castration-Resistant Prostate Cancer: A Meta-Analysis

New treatments, such as sipuleucel-T and androgen receptor- (AR-) directed therapies (enzalutamide (Enz) and abiraterone acetate (AA)), have emerged and been approved for the management of castration-resistant prostate cancer (CRPC). There are still debates over their efficacy and clinical benefits. This meta-analysis aimed to investigate the efficacy and safety of sipuleucel-T and AR-directed therapies in patients with CRPC. RevMan 5.1 was used for pooled analysis and analysis of publication bias. Seven studies were included in the meta-analysis, with three studies in sipuleucel-T (totally 737 patients, 488 patients in treatment group, and 249 patients in placebo group) and four in AR-directed therapies (totally 5,199 patients, 3,015 patients in treatment group, and 2,184 patients in placebo group). Treatment with sipuleucel-T significantly improved overall survival in patients with CRPC and was not associated with increased risk of adverse event of grade ≥3 (p > 0.05). However, treatment with sipuleucel-T did not improve time-to-progression and reduction of prostate-specific antigen (PSA) level ≥50% was not significantly different from that with placebo. AR-directed therapies significantly improved overall survival in patients with CRPC and improved time-to-progression and reduction of PSA level ≥50%. AR-directed therapies did not increase risk of adverse event of grade ≥3 (p > 0.05).

The safety and efficacy of radium-223 dichloride for the treatment of advanced prostate cancer

INTRODUCTION

A number of drugs have been shown to extend life expectancy in castration-resistant prostate cancer (CRPC). Skeletal related events (SREs) secondary to bone metastases cause significant morbidity for men with CRPC. The α-emitting radiopharmaceutical radium-223 dichloride has been shown to improve overall survival, time to symptomatic skeletal events (SSEs) and quality of life in CRPC.

AREAS COVERED

The development of radium-223 from pre-clinical studies to the evidence of efficacy and safety from a phase 3 trial is discussed as well as its pharmacokinetics and metabolism. The integration of radium-223 into routine care for patients with advanced prostate cancer is included including a comparison with other agents in this setting. Expert commentary: The risk/benefit ratio for radium-223 is very similar to that of other agents used in the CRPC setting and is a treatment option for men unsuitable for cytotoxic chemotherapy because of comorbidities. The ALSYMPCA trial demonstrated an improvement in SSEs with radium-223. This is a clinically relevant end-point as not all radiologically-detected SREs are apparent to patients. The correct sequencing of the life-prolonging treatments available to men with CRPC is subject to debate. Radium-223 therapy should be considered before the development of visceral metastases. Drug-combination studies are underway.

[Therapy of bone metastases with radium-223. German guidelines]

This document describes the guideline for therapy of bone metastases with radium-223 ((223)Ra) published by the Arbeitsgemeinschaft der Wissenschaftlichen Medizinischen Fachgesellschaften in Germany (AWMF) under the auspices of the Deutsche Gesellschaft für Nuklearmedizin (DGN), Östereichische Gesellschaft für Nuklearmedizin (OGN), and Schweizerische Gesellschaft für Nuklearmedizin (SGNM). This guidance is based on an interdisciplinary consensus. These recommendations are a prerequisite for the quality management in the treatment of patients with bone metastases from prostate cancer using (223)Ra. They are aimed at guiding nuclear medicine specialists in selecting candidates to receive therapy and to deliver the treatment in a safe and effective manner. The document contains background information and definitions. It covers the rationale, indications and contraindications for therapy with (223)Ra. Essential topics are the requirements for institutions performing the therapy, which patient data have to be available prior to performance of therapy, and how treatment has to be carried out technically and organisationally. Moreover, essential elements of follow-up and aftercare are specified. As a matter of principle, the treatment inclusive aftercare has to be realised in close cooperation with the involved medical disciplines.

223Ra α-Therapy in Patients with Bone Metastases from Castration-resistant Prostate Cancer

In developed countries such as Canada, the lifetime risk of prostate cancer is about one in six, with a 30% chance of relapse with bone metastases in each case. Bone involvement not only decreases prognosis, but also increases the likelihood of many other medical ailments. There currently exist numerous treatment options for pain palliation for these patients. Common options include chemotherapy, external beam radiotherapy, bisphosphonates, and radionuclide therapy with strontium 89. Each variation, however, shows clear drawbacks. A type of radionuclide therapy, newly approved in Canada, using alpha particles from radium 223 is showing promise. Unlike the previously mentioned therapies, radium 223 is the only one that excels in all desirable aspects for palliation therapy. Radium 223 not only decreases or eliminates metastases-related bone pain, but also has a great safety profile, increases the average length of survival, and exhibits areas of cost-effectiveness. Radium 223 also delays skeletal-related events and prostate-specific antigen elevation, representing a noteworthy breakthrough for bone-targeted radionuclide therapies.

Radium-223 in the treatment of osteoblastic metastases: a critical clinical review

The element radium (Ra) was discovered by the Curies in 1898 and within a decade was in broad scientific testing for the management of several forms of cancer. The compound was known to give rise to a series of both high-energy particulate and penetrating γ-emissions. The latter found an important role in early 20th century brachytherapy applications, but the short-range α-particles seemed much less useful. Although highly cytotoxic when released within a few cell diameters of critical cell nuclei, the dense double-strand break damage was poorly repaired, and concerns regarding treatment-related toxicities and secondary malignancies halted clinical development. Moreover, the most common isotope of Ra has an exceptionally long half-life (>1600 years for (226)Ra) that proved daunting when aiming for a systemic cancer therapy. Fortunately, other radium isotopes have more convenient half-lives while still producing cytotoxic α particles. Radium-223 dichloride has a half-life of 11.4 days, and this isotope was identified as an excellent candidate for radionuclide therapy of cancers metastatic to bone. The calcium-mimetic chemical properties of the radium allowed intravenous infusion with rapid uptake to sites of new bone formation. The highly efficient bone localization suggested a potential therapeutic role for osteoblastic bone metastases, and a series of phase 1, 2, and 3 clinical trials was undertaken to explore this possibility. This series of clinical explorations culminated in the ALSYMPCA trial, an international, placebo-controlled, phase 3 study that accrued 921 symptomatic men with bone-metastatic, castrate-resistant prostate cancer. Results of this trial demonstrated a prolongation of overall survival, and regulatory agencies around the world have now approved this product as a treatment for advanced prostate cancer.

Treatment of castration-resistant prostate cancer and bone metastases with radium-223 dichloride

Radium-223 dichloride (Ra-223) is the first α-particle emitting radiopharmaceutical to be approved for the treatment of patients with castration-resistant prostate cancer and associated bone metastases, and the first bone-targeting agent to significantly improve patient overall survival whilst reducing pain and the symptomatic skeletal events (SSEs) associated with bone metastases. Ra-223 exhibits a favourable safety profile, with low myelosuppression rates and fewer adverse events than placebo. Compared with other approved radiopharmaceuticals, the α-particle emitting Ra-223 has a high biological efficiency and a short penetration range, potentially sparing bone marrow toxicity and limiting unwanted exposure. Ra-223 has a short half-life and decays to a stable product, reducing the problem of storage and disposal associated with radiopharmaceuticals. Ra-223 offers a new treatment option with great potential in this setting. However, concerns remain amongst patients, their families and health care professionals over the use of radiopharmaceuticals. This article, which draws on the experiences of health care workers during the ALSYMPCA (ALpharadin in SYMtomatic Prostate CAncer) study, reviews the clinical development of Ra-223, highlighting the key issues for the uro-oncology nurse who has a pivotal role within the multi-disciplinary team (MDT) to ensure safe and effective treatment to the patient. The role of the uro-oncology nurse is multifaceted, including patient pre-assessment and post-treatment monitoring and coordination of the MDT. In addition, their role in communicating with and educating those involved with Ra-223 on what to expect from the agent can alleviate fears associated with its use.

Evolving treatment approaches for the management of metastatic castration-resistant prostate cancer - role of radium-223

Radium-223 is a first-in-class alpha particle-emitting radiopharmaceutical approved for the treatment of bone metastatic castration-resistant prostate cancer. Radium-223 is administered intravenously with no requirement for complex shielding and specifically targets areas of bone metastasis. In a randomized placebo-controlled Phase III study, treatment with radium-223 was shown to improve overall survival, time to skeletal-related events, and health-related quality of life. Apart from radium-223, the cytotoxic chemotherapy agents docetaxel and cabazitaxel, androgen biosynthesis inhibitor abiraterone acetate, novel anti-androgen enzalutamide, and immunotherapy sipuleucel-T have also been shown to improve survival of men with advanced prostate cancer in Phase III trials. This review will outline current treatment approaches for advanced prostate cancer with a focus on the role of radium-223 in changing treatment paradigms.