Palliative care of bone pain due to skeletal metastases: Exploring newer avenues using neutron activated (45)Ca

[Evaluation of radionuclide impurities in several radiopharmaceuticals]

PURPOSE

Revisions to German radiation protection laws have resulted in updated limit values, which could affect the unrestricted release of waste produced by nuclear medicine therapy. In addition, signs of long-lived concomitant nuclides in ¹⁵³Sm and ²²³Ra radiopharmaceuticals have been seen in the past. Therefore, the goal of this article was to analyze the radionuclidic purity of selected radiopharmaceuticals.

METHOD

48 samples from 12 different radiopharmaceuticals were examined. A high purity germanium semiconductor detector (HPGe detector) was used for the qualitative and quantitative evaluation of concomitant nuclides.

RESULTS

Various europium isotopes were identified in ⁹⁰Y-citrate, ¹⁵³Sm-Quadramet, ¹⁶⁶Ho-QuiremSpheres, and ¹⁶⁹Er-erbium citrate, with the greatest amount being found in ¹⁵³Sm (7.0 ppm (¹⁵²Eu), 8.4 ppm (¹⁵⁴Eu), and 2.1 ppm (¹⁵⁵Eu)). ¹⁶⁹Yb was the most significant impurity in ¹⁶⁹Er (513 ppm). In the case of ¹⁷⁷Lu radiopharmaceuticals, there was a significant difference in the ^177mLu content (0.8 ppm vs. 0.0024 ppm) between two different manufacturers. No concomitant nuclides could be found within the detection limits in the case of ⁹⁰Y spheres, ²²³Ra, and ²²⁵Ac.

CONCLUSION

The limit values for unrestricted release are exceeded manyfold in the case of the identified concomitant nuclides. As a result, alternative release procedures (extension of the decay time, specific release, release in the individual case) or transfer to collection facilities must be considered. Technical methods for reducing or preventing impurities could also be a possible solution. Consequences for patient radiation exposure were able to be ruled out.

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.