# Radium-223

Source: https://nuclide.cc/isotopes/ra-223/  
Nuclide record `ra-223` (Isotope). Data CC BY-NC 4.0, attribute "Data from Nuclide (nuclide.cc)"; commercial use needs a licence.

## TL;DR

A radioactive form of the mineral radium that behaves like calcium and settles into bone. It gives off very short-range, high-energy particles that damage cancer growing in bone while barely reaching the healthy marrow next to it.

## Summary

Radium-223 dichloride (Xofigo) is a calcium mimetic that concentrates in areas of increased bone turnover, such as osteoblastic bone metastases. It decays through a six-stage chain to stable lead-207, emitting predominantly alpha particles (95.3% of emitted energy), with small beta (3.6%) and gamma (1.1%) contributions from itself and its short-lived daughters (polonium-215, lead-211, bismuth-211, thallium-207).

The alpha range is under 100 micrometres in tissue (maximum about 6.2 cm in air), so the dose is deposited within roughly the width of a few cells of the bone surface, largely sparing the adjacent marrow. It was the first alpha-emitting radiopharmaceutical to gain FDA and EMA approval, on the strength of the ALSYMPCA trial's overall-survival benefit in metastatic castration-resistant prostate cancer with symptomatic bone metastases and no known visceral disease.

Ra-223 is obtained from a generator chain rooted in actinium-227 (itself made by neutron irradiation of radium-226 in a reactor); Ac-227 beta-decays to thorium-227, which alpha-decays to Ra-223. Commercial-scale 223Ra is available from Bayer's own supply chain and, more broadly, ORNL, PNNL and Rosatom hold production capability; a 2025 review (the PSI-led 'Alpha Atlas') judged that, unlike most other alpha emitters, 223Ra supply is adequate to global demand and no near-term shortage is expected.

## Fields

- Kind: Isotope
- Status: approved
- Last checked: 2026-09-22
- Also known as: 223Ra; Ra-223
- Tags: therapy; alpha emitter; bone-seeking

## Sources

- FDA label: Xofigo (radium Ra 223 dichloride): https://www.accessdata.fda.gov/drugsatfda_docs/label/2013/203971lbl.pdf
- Radium-223 mechanism of action (Nature Reviews Urology, 2019): https://pmc.ncbi.nlm.nih.gov/articles/PMC7515774/
- Production and supply of alpha particle emitting radionuclides for TAT (JNM, 2021): https://jnm.snmjournals.org/content/jnumed/early/2021/07/22/jnumed.120.261016.full.pdf
- Alpha Atlas: mapping global production of alpha-emitting radionuclides for TAT (PSI, 2025): https://www.dora.lib4ri.ch/psi/islandora/object/psi:68199/datastream/PDF/Tosato-2025-Alpha_Atlas-(published_version).pdf

## Connected records

- drugs: [Radium-223 dichloride](https://nuclide.cc/drugs/radium-223/), [Samarium-153 lexidronam](https://nuclide.cc/drugs/samarium-153-lexidronam/), [Strontium-89 chloride](https://nuclide.cc/drugs/sr-89-chloride/)
- trials: [ALSYMPCA](https://nuclide.cc/trials/alsympca/)
- key papers: [ALSYMPCA: alpha emitter radium-223 and survival in metastatic prostate cancer with bone metastases](https://nuclide.cc/key-papers/paper-alsympca-radium-223-nejm-2013/), [Radiopharmaceutical therapy in cancer: clinical advances and challenges](https://nuclide.cc/key-papers/paper-sgouros-tat-review-nat-rev-2020/)
- terms: [Alpha vs beta emitters](https://nuclide.cc/terms/alpha-vs-beta/), [Bone metastases and skeletal-related events](https://nuclide.cc/terms/bone-metastases/), [Flare phenomenon](https://nuclide.cc/terms/flare-phenomenon/), [mCRPC and mHSPC (castration-resistant vs hormone-sensitive prostate cancer)](https://nuclide.cc/terms/mcrpc-mhspc/)
- isotopes: [Strontium-89](https://nuclide.cc/isotopes/sr-89/), [Thorium-227](https://nuclide.cc/isotopes/th-227/)
- technologies: [Macropa chelation](https://nuclide.cc/technologies/macropa-chelation/), [Targeted alpha therapy](https://nuclide.cc/technologies/targeted-alpha-therapy/)
- indications: [Bone pain palliation from osteoblastic metastases](https://nuclide.cc/indications/bone-pain-palliation/), [Metastatic castration-resistant prostate cancer](https://nuclide.cc/indications/prostate-mcrpc/), [Osteosarcoma](https://nuclide.cc/indications/osteosarcoma/), [Prostate cancer](https://nuclide.cc/indications/prostate/)
- companies: [Bayer](https://nuclide.cc/companies/bayer/)
- institutions: [Oslo University Hospital, The Norwegian Radium Hospital](https://nuclide.cc/institutions/oslo-radium-hospital/)
- roadmaps: [Alpha-emitter roadmap: radium-223 → 225Ac-PSMA-617 → a phase 3 pipeline](https://nuclide.cc/roadmaps/alpha-therapy-roadmap/), [Radiopharmaceutical roadmap: iodine → lutetium → actinium](https://nuclide.cc/roadmaps/radiopharma-roadmap/)
- collections: [Prostate Cancer Foundation (PCF)](https://nuclide.cc/collections/prostate-cancer-foundation/)
- people: [A. Oliver Sartor](https://nuclide.cc/people/oliver-sartor/), [Chris C. Parker](https://nuclide.cc/people/chris-parker/), [Karim Fizazi](https://nuclide.cc/people/karim-fizazi/)
- fronts: [Bone-targeted radiopharmaceuticals](https://nuclide.cc/fronts/f-bone-targeted/), [Targeted alpha therapy](https://nuclide.cc/fronts/f-alpha-therapy/)
- pairings: [Radium-223 with abiraterone: a caution, not a combination](https://nuclide.cc/pairings/radium223-abiraterone-caution/)
- targets: [Bone mineral (hydroxyapatite)](https://nuclide.cc/targets/bone-hydroxyapatite/)

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