Guest Editorial

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Nuclear medicine offers both diagnostic and therapeutic procedures. Up to 10 years ago, the therapeutic spectrum primarily covered benign and malignant thyroid diseases. Additionally, relatively few patients were treated with ⁸⁹Sr for bone pain palliation or with radioactive colloids for malignant pleural or peritoneal metastatic spread. However, the last years have witnessed a proliferation of additional techniques that have enhanced our therapeutic capabilities. With the advent of Zevalin, ⁹⁰Y DOTATOC, and selective internal radiation therapy (SIRT), the importance of nuclear medicine therapy has increased considerably. This issue of Seminars in Nuclear Medicine will summarize the progress and potential of therapeutic radioisotopes.

Radioiodine therapy of thyroid cancer has been used for more than 65 years. During the last 2 decades, some modifications have been made, including redifferentiation therapy and anticancer drugs. However, in principle, this kind of treatment had not been changed significantly during the last 30 or 40 years.

Radioisotope therapy for palliation of painful bone metastases has also been in use for 4 or 5 decades, initially with ³²P, and subsequently with ⁸⁹Sr. Newer developments include rhenium and samarium radioisotopes that also allow “sequential” application with higher success rates.

Meta-iodobenzylguanidine diagnosis of neuroendocrine tumors dates back to the beginning of the 1980s, and only a few years later this radioisotope was used for the treatment of neuroblastoma and pheochromocytoma. Another step forward was the development of ⁹⁰Y DOTATOC and ¹⁷⁷Lu DOTATATE, allowing a receptor-mediated approach. This procedure has added a new dimension to the treatment of advanced and metastatic neuroendocrine tumors. Although complete remissions are rare, the newest data suggest that the quality of life and the survival rate can be significantly improved.

More than 50 years ago, radioimmunoscintigraphy was introduced into nuclear medicine. Now, radioimmunotherapy has been added to the capabilities of nuclear medicine. For the past several years, FDA and EMEA-approved radiopharmaceuticals have been available for the treatment of non-Hodgkin lymphoma. Two articles in this Seminar deal with this important aspect of nuclear medicine therapy.

Another procedure, which is now being increasingly used, is intra-arterial therapy of both primary liver cancer and metastases. The development of the respective pharmaceuticals took more than 20 years since the first published use of radiomicrospheres for this purpose. The first clinical studies combining chemotherapy and SIRT as a first-line therapy procedure in liver metastases of colorectal cancer have been initiated.

Because of the strict radiation safety regulations in Europe, metabolic therapy is part of nuclear medicine. The situation in the United States is different as metabolic radiotherapy is also practised by radiation oncologists. Especially in Germany, molecular radiotherapy is of paramount importance because the patients have to be hospitalized and treated as inpatients for several days. Interestingly, as the number of radioiodine therapies in benign thyroid diseases has gone down by 10%-15% after inaugurating iodine prophylaxis in Germany, there is now ample hospital bed space available for nonradioiodine therapeutic procedures. The Department of Nuclear Medicine of the University of Bonn is treating about 1200 cases per year, with more than 50% of the patients coming from oncology. We are currently treating 70-80 neuroendocrine patients (180-200 therapies) per year with radiopeptide therapy. Additionally, we perform approximately 120 SIRT treatments per year. Although the radiation safety requirements are different in the United States and other parts of the world, we have to face the fact that metabolic radiotherapy has broadened the spectrum of nuclear medicine and has also increased the need for functional imaging, for example, FDG-PET and choline-PET before and after treatment, as well as whole body imaging with ⁶⁸Ga DOTATATE after therapy of neuroendocrine tumors. Although the nuclear medicine specialist is competing with radiology and ultrasound in the field of diagnosis, especially SIRT requires the close cooperation of radiology and nuclear medicine.

We hope that this review of current metabolic therapy procedures will stimulate our colleagues all over the world to use these procedures more often. Of course, special training for nurses, technologists, and physicians is necessary. For many years, nuclear medicine was limited to radioiodine therapy of benign and malignant thyroid diseases. Now, the increased use of oncological therapeutic methods will certainly enhance the importance of nuclear medicine in clinical medicine.