Comparative analysis of 11 different radioisotopes for palliative treatment of bone metastases by computational methods

An assessment of bone-seeking radionuclides for palliation of metastatic bone pain in a vertebral model

OBJECTIVE

Bone-seeking radiopharmaceuticals have the main role in the treatment of painful bone metastases. The aim of this study was to dosimetrically compare radiopharmaceuticals in use for bone pain palliation therapy and bone scan.

METHODS

The MCNPX code was used to simulate the radiation transport in a vertebral phantom. Absorbed fractions were calculated for monoenergetic electrons, photons and alpha particles. S values were obtained for radionuclides ³²P, ³³P, ⁸⁹Sr, ⁹⁰Y, ^99mTc, ^117mSn, ¹⁵³Sm, ¹⁶⁶Ho, ¹⁶⁹Er, ¹⁷⁷Lu, ¹⁸⁶Re, ¹⁸⁸Re, ²²³Ra, ²²⁴Ra and their progenies for target regions including the active marrow and the bone endosteum.

RESULTS

The results demonstrated the dependence of dosimetric parameters on the source or target size, particle energy and location of the source. The electron emitters including ³³P, ^117mSn, ¹⁶⁹Er and ¹⁷⁷Lu and ²²³Ra as an α-emitter gave the lower absorbed dose to the active marrow. These radionuclides gave the highest values of the Relative Advantage Factor (RAF).

CONCLUSIONS

According to the results, ³³P, ^117mSn, ¹⁶⁹Er, ¹⁷⁷Lu and ²²³Ra have fewer side effects on the active marrow than other investigated radionuclides. Therefore, these radionuclides may be a better choice for use in palliative radiotherapy.

Evolution of Cancer Pharmacological Treatments at the Turn of the Third Millennium

The medical history of cancer began millennia ago. Historical findings of patients with cancer date back to ancient Egyptian and Greek civilizations, where this disease was predominantly treated with radical surgery and cautery that were often ineffective, leading to the death of patients. Over the centuries, important discoveries allowed to identify the biological and pathological features of tumors, without however contributing to the development of effective therapeutic approaches until the end of the 1800s, when the discovery of X-rays and their use for the treatment of tumors provided the first modern therapeutic approach in medical oncology. However, a real breakthrough took place after the Second World War, with the discovery of cytotoxic antitumor drugs and the birth of chemotherapy for the treatment of various hematological and solid tumors. Starting from this epochal turning point, there has been an exponential growth of studies concerning the use of new drugs for cancer treatment. The second fundamental breakthrough in the field of oncology and pharmacology took place at the beginning of the '80s, thanks to molecular and cellular biology studies that allowed the development of specific drugs for some molecular targets involved in neoplastic processes, giving rise to targeted therapy. Both chemotherapy and target therapy have significantly improved the survival and quality of life of cancer patients inducing sometimes complete tumor remission. Subsequently, at the turn of the third millennium, thanks to genetic engineering studies, there was a further advancement of clinical oncology and pharmacology with the introduction of monoclonal antibodies and immune checkpoint inhibitors for the treatment of advanced or metastatic tumors, for which no effective treatment was available before. Today, cancer research is always aimed at the study and development of new therapeutic approaches for cancer treatment. Currently, several researchers are focused on the development of cell therapies, anti-tumor vaccines, and new biotechnological drugs that have already shown promising results in preclinical studies, therefore, in the near future, we will certainly assist to a new revolution in the field of medical oncology.

Gaussian plume atmospheric modelling and radiation exposure calculations following the cremation of a deceased thyroid cancer patient treated with iodine-131

Shortly after treatment with 7200 MBq of ¹³¹I, a thyroid cancer patient died and was subsequently cremated. Calculations of the atmospheric emissions of ¹³¹I from the crematorium flue were performed using a standard atmospheric pollution Gaussian Plume Dispersal model. Estimates of whole-body and thyroid dose of those potentially exposed were made using OLINDA/EXM dosimetry software. Under the meteorological conditions prevalent at the time of the cremation, and depending on the actual release rate of the ¹³¹I, the Western Australian legal limit of 3.7 Bqm^-3 for atmospheric emissions of ¹³¹I may have been exceeded for distances of up to 440 and 1610 m downwind of the crematorium chimney, with the maximum concentration being between 33 and 392 Bqm^-3. Assuming 16% of the inhaled ¹³¹I was taken up in the thyroid with the balance in the remainder of the body, the radiation dose to maximally exposed individuals was calculated to be approximately 17.7 μSv to the thyroid and 0.04 μSv to the whole-body. Despite the maximum allowable atmospheric ¹³¹I concentration of 3.7 Bqm^-3 being exceeded, as the number of people immediately downwind of the crematorium flue in the high concentration zones was very low, and considering the relatively high tolerable dose to the thyroid, the radiation dose to people was probably not a problem in this case. The local limit of 1000 MBq of ¹³¹I for the cremation of a deceased patient is reasonable, but with adequate precautions could be significantly increased without any harmful effects to people or the environment.

Computational modeling of radiobiological effects in bone metastases for different radionuclides

PURPOSE

Computational simulation is a simple and practical way to study and to compare a variety of radioisotopes for different medical applications, including the palliative treatment of bone metastases. This study aimed to evaluate and compare cellular effects modelled for different radioisotopes currently in use or under research for treatment of bone metastases using computational methods.

METHODS

Computational models were used to estimate the radiation-induced cellular effects (Virtual Cell Radiobiology algorithm) post-irradiation with selected particles emitted by Strontium-89 (⁸⁹Sr), Samarium-153 (¹⁵³Sm), Lutetium-177 (¹⁷⁷Lu), and Radium-223 (²²³Ra).

RESULTS

Cellular kinetics post-irradiation using ⁸⁹Sr β^- particles, ¹⁵³Sm β^-particles, ¹⁷⁷Lu β^-particles and ²²³Ra α particles showed that the cell response was dose- and radionuclide-dependent. ¹⁷⁷Lu beta minus particles and, in particular, ²²³Ra alpha particles, yielded the lowest survival fraction of all investigated particles.

CONCLUSIONS

²²³Ra alpha particles induced the highest cell death of all investigated particles on metastatic prostate cells in comparison to irradiation with β^-radionuclides, two of the most frequently used radionuclides in the palliative treatment of bone metastases in clinical routine practice. Moreover, the data obtained suggest that the used computational methods might provide some perception about cellular effects following irradiation with different radionuclides.

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.

Harnessing the bone-seeking ability of Ca(ii)-like metal ions in the treatment of metastatic cancer and resorption disorders

In this tutorial review, we explore how a special relationship between metal ions and bones has been exploited to target therapeutic agents.

Comparative analysis of 11 different radioisotopes for palliative treatment of bone metastases by computational methods

PURPOSE

Throughout the years, the palliative treatment of bone metastases using bone seeking radiotracers has been part of the therapeutic resources used in oncology, but the choice of which bone seeking agent to use is not consensual across sites and limited data are available comparing the characteristics of each radioisotope. Computational simulation is a simple and practical method to study and to compare a variety of radioisotopes for different medical applications, including the palliative treatment of bone metastases. This study aims to evaluate and compare 11 different radioisotopes currently in use or under research for the palliative treatment of bone metastases using computational methods.

METHODS

Computational models were used to estimate the percentage of deoxyribonucleic acid (DNA) damage (fast Monte Carlo damage algorithm), the probability of correct DNA repair (Monte Carlo excision repair algorithm), and the radiation-induced cellular effects (virtual cell radiobiology algorithm) post-irradiation with selected particles emitted by phosphorus-32 ((32)P), strontium-89 ((89)Sr), yttrium-90 ((90)Y ), tin-117 ((117m)Sn), samarium-153 ((153)Sm), holmium-166 ((166)Ho), thulium-170 ((170)Tm), lutetium-177 ((177)Lu), rhenium-186 ((186)Re), rhenium-188 ((188)Re), and radium-223 ((223)Ra).

RESULTS

(223)Ra alpha particles, (177)Lu beta minus particles, and (170)Tm beta minus particles induced the highest cell death of all investigated particles and radioisotopes. The cell survival fraction measured post-irradiation with beta minus particles emitted by (89)Sr and (153)Sm, two of the most frequently used radionuclides in the palliative treatment of bone metastases in clinical routine practice, was higher than (177)Lu beta minus particles and (223)Ra alpha particles.

CONCLUSIONS

(223)Ra and (177)Lu hold the highest potential for palliative treatment of bone metastases of all radioisotopes compared in this study. Data reported here may prompt future in vitro and in vivo experiments comparing different radionuclides for palliative treatment of bone metastases, raise the need for the careful rethinking of the current widespread clinical use of (89)Sr and (153)Sm, and perhaps strengthen the use of (223)Ra and (177)Lu in the palliative treatment of bone metastases.