内容紹介
Cancer Therapy Using Unsealed Radioisotopes―The Present and Future
Summary
Iodine-131(I-131)has been used for the ablation of residual thyroid remnants and cancer cells in well-differentiated thyroid cancers. It has also been used for metastatic well-differentiated thyroid cancers, especially lung and bone metastases. For small lung metastases, I-131 treatment has curative potential, particularly in young patients. Suppression of the thyroid stimulating hormone is also important for prolonging the survival of thyroid cancer patients.
Strontium-89(Sr-89)chloride has a mechanism similar to calcium, and it has been used for the treatment of bone metastases, especially osteoblastic metastases. It has been reported to have analgesic effects in an average of 76% of cases, and it is more effective if used in the early bone metastatic phase. Ibritumomab tiuxetan(Zevalin)is an anti-CD20 mouse monoclonal antibody labeled with Yttrium-90(Y-90). It is used for treatment-resistant low grade or follicular B-cell non-Hodgkin's lymphomas and mantle lymphomas. Recently, radium-223(Ra-223)has been used for bone metastases from castration-resistant prostate cancers, and in a phase Ⅲ trial, it has been proven to prolong survival of these patients.
Cancer therapy using unsealed radioisotopes has been thought to be promising because it exhibits more targeted therapy than external beam irradiation. Therefore, if many more ideal targeting agents are developed in the future, this treatment might be used more commonly. As many agents such as I-131, Sr-89, and Ra-223 are available for treating bone metastasis, the combined use of other treatments such as high precision radiotherapy, bisphosphonates, hormonal agents, and molecular targeted agents should be investigated.
要旨
非密封放射性同位元素を経口的もしくは経静脈的に投与し,親和性の高い組織もしくは腫瘍に取り込ませて放射線治療を行うという治療が,もうすでに半世紀以上続いている。病変部分に選択的に集積され,そこで放射線が投与されるので,その線量分布は外部照射による高精度放射線治療に劣らないと考えられる。その代表は分化型甲状腺癌に対するI-131治療で,濾胞癌および一部の乳頭癌において用いられている。また,造骨性の骨転移に投与するSr-89や治療抵抗性の低悪性度または濾胞性B細胞性非ホジキンリンパ腫,マントルリンパ腫などの悪性リンパ腫に用いられるY-90を使用したイブリツモマブ(ゼヴァリン)も有名である。最近,Ra-223を用いたXofigo(Alpharadin)という製剤にも去勢抵抗性前立腺癌の骨転移治療に期待がもたれている。これらの4薬剤のうち,骨転移に対しては3種の薬剤がある。さらに高精度放射線治療の普及によって,特殊な治療方法も適応になってきた。今後ますます集学的治療が用いられるようになっていくと考えられる。
目次
Summary
Iodine-131(I-131)has been used for the ablation of residual thyroid remnants and cancer cells in well-differentiated thyroid cancers. It has also been used for metastatic well-differentiated thyroid cancers, especially lung and bone metastases. For small lung metastases, I-131 treatment has curative potential, particularly in young patients. Suppression of the thyroid stimulating hormone is also important for prolonging the survival of thyroid cancer patients.
Strontium-89(Sr-89)chloride has a mechanism similar to calcium, and it has been used for the treatment of bone metastases, especially osteoblastic metastases. It has been reported to have analgesic effects in an average of 76% of cases, and it is more effective if used in the early bone metastatic phase. Ibritumomab tiuxetan(Zevalin)is an anti-CD20 mouse monoclonal antibody labeled with Yttrium-90(Y-90). It is used for treatment-resistant low grade or follicular B-cell non-Hodgkin's lymphomas and mantle lymphomas. Recently, radium-223(Ra-223)has been used for bone metastases from castration-resistant prostate cancers, and in a phase Ⅲ trial, it has been proven to prolong survival of these patients.
Cancer therapy using unsealed radioisotopes has been thought to be promising because it exhibits more targeted therapy than external beam irradiation. Therefore, if many more ideal targeting agents are developed in the future, this treatment might be used more commonly. As many agents such as I-131, Sr-89, and Ra-223 are available for treating bone metastasis, the combined use of other treatments such as high precision radiotherapy, bisphosphonates, hormonal agents, and molecular targeted agents should be investigated.
要旨
非密封放射性同位元素を経口的もしくは経静脈的に投与し,親和性の高い組織もしくは腫瘍に取り込ませて放射線治療を行うという治療が,もうすでに半世紀以上続いている。病変部分に選択的に集積され,そこで放射線が投与されるので,その線量分布は外部照射による高精度放射線治療に劣らないと考えられる。その代表は分化型甲状腺癌に対するI-131治療で,濾胞癌および一部の乳頭癌において用いられている。また,造骨性の骨転移に投与するSr-89や治療抵抗性の低悪性度または濾胞性B細胞性非ホジキンリンパ腫,マントルリンパ腫などの悪性リンパ腫に用いられるY-90を使用したイブリツモマブ(ゼヴァリン)も有名である。最近,Ra-223を用いたXofigo(Alpharadin)という製剤にも去勢抵抗性前立腺癌の骨転移治療に期待がもたれている。これらの4薬剤のうち,骨転移に対しては3種の薬剤がある。さらに高精度放射線治療の普及によって,特殊な治療方法も適応になってきた。今後ますます集学的治療が用いられるようになっていくと考えられる。