The role of electron-emitting radiopharmaceuticals in the palliative treatment of metastatic bone pain and for radiosynovectomy: applications of conversion electron emitter Tin-117m

A variety of radionuclides continue to be investigated and/or clinically used for different therapeutic applications in nuclear medicine. The choice of a particular radionuclide with regard to appropriate emissions, linear energy transfer (LET), and physical half-life, etc., is dictated to a large extent by the character of the disease (e.g., solid tumor or metastatic disease), and by the carrier to selectively transport the radionuclide to the desired site. An impressive body of information has appeared in the recent literature that addresses many of these considerations. This article summarizes and discusses the role of high-LET electron emitters and their advantage in the treatment of cancer or for other disorders in specific situations. Areas such as bone pain palliation, bone malignancy therapy, and radiation synovectomy are covered in greater detail. Projections are made as to the future directions and progress in these areas. A discussion of the various issues related to the selection criteria that are useful for choosing the appropriate radionuclide for a particular application is included. Use of high-LET electron emitters is discussed in greater detail, with particular emphasis on the use of conversion electron emitter tin-117m for various therapeutic applications.

Uma variedade de radionuclídeos continua a ser investigada e/ou clinicamente utilizada para diferentes aplicações terapêuticas em medicina nuclear. A escolha de um radionuclídeo, considerando-se sua emissão apropriada, transferência linear de energia (LET) e meia-vida física é determinada na maior parte pelo caráter da doença (p.ex., tumor sólido ou doença metastática), e pelo carreador que transporta o radionuclídeo seletivamente para o sítio desejado. Um notável conjunto de informações voltadas para essas considerações tem aparecido na literatura recente. Esse trabalho resume e discute o papel de emissores de elétrons de alta-LET e sua vantagem no tratamento do câncer ou para outras doenças em situações específicas. Abordagens relacionadas com o alívio da dor óssea, a terapia da doença óssea e a sinovectomia por radiação são apresentadas detalhadamente. Projeções para o futuro e os progressos nessas áreas são indicadas. Uma profunda discussão relacionada aos critérios de seleção que são úteis para escolher o radionuclídeo apropriado para que uma aplicação particular seja incluída. O uso de emissores de elétrons de alta-LET é discutido em grande detalhe, com particular ênfase no uso do estanho-117m, um emissor de elétron de conversão, para várias aplicações terapêuticas.

Bone-seeking therapeutic radiopharmaceuticals

Bone-seeking therapeutic radiopharmaceuticals are utilized on the basis of the radionuclideÆs particulate emissions (primarily low to intermediate beta emission). The requirements therefore are different from those of bone imaging agents that consist mainly of short-lived single photon emitters. Lately, the therapeutic bone seeking radiopharmaceuticals have attained increasing importance due to their potential role in alleviating pain from osseous metastases in cancer patients, for the treatment of joint pain resulting from inflamed synovium (radiosynoviorthesis, or radiosynovectomy), or from various other forms of arthritic disease. There is, however, a paucity of published data on the bio-pharmacokinetics of these agents when used following intravenous administration for bone pain palliation. This paper will briefly review and summarize the presently available chemical and biopharmacokinetic information on the various clinically approved as well as experimental bone-localizing therapeutic radiopharmaceuticals, and make projections on their clinical application for the treatment of primary/metastatic cancer in bone