• Massimiliano Pacilio
  • Elisabetta Verdolino
  • Bartolomeo Cassano
  • Giuseppe De Vincentis


Improved overall survival and very low toxicity indicate that 223Ra-dichloride therapy may provide a new standard of care for patients with castration-resistant prostate cancer metastatic to the bone. The high linear energy transfer (LET) of α-radiation results in greater biological effectiveness than β-radiation, giving rise to cytotoxicity that is independent of dose rate, cell cycle growth phase, and oxygen concentration. Due to the α-particle high LET and short range (of a few cell diameters in tissue), microdosimetry seems almost always necessary; however, the feasibility of macrodosimetry for organs and lesions has recently been demonstrated, providing new opportunities in the clinical routine not yet explored. With the low activity of the registered use, bone lesion macrodosimetry appeared more feasible than organ dosimetry and more effective for investigating possible relationships between absorbed dose and biological/clinical effect, as response is often observed in clinical practice, whereas toxicities are mild to moderate in intensity and easily manageable with symptomatic and supportive treatments. The first injection of the treatment can be used as if it were a pretreatment tracer activity, and just three scan acquisitions are required (with a duration of about 20–30 min each), as well as other conventional imaging (such as 99mTc-diphosphonate WB scan and CT study), with a limited burden for patients and staff. A lesion/soft tissue contrast ratio on 99mTc-MDP WB scan higher than 10 would imply detectability on 223Ra spot scans. A specific preparation of the patient is not required, apart from the necessary informed consent. The correlations of the absorbed dose to lesions with the biological/clinical effects are still under consideration; however, in the perspective of the availability of new fractionation regimens, the dosimetric approach would allow a dosimetry-based choice of the administration scheduling, opening the way to dosimetry-guided radiometabolic therapy of bone metastases with α-emitters.


Bone metastases 223Ra-dichloride Radionuclide therapy Dosimetry 


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Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  • Massimiliano Pacilio
    • 1
  • Elisabetta Verdolino
    • 2
  • Bartolomeo Cassano
    • 2
  • Giuseppe De Vincentis
    • 3
  1. 1.Department of Medical PhysicsAzienda Ospedaliera Universitaria Policlinico Umberto IRomeItaly
  2. 2.Postgraduate School of Medical Physics, “Sapienza” University of RomeRomeItaly
  3. 3.Department of Radiological, Oncological and Anatomo Pathological Sciences“Sapienza” University of RomeRomeItaly

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