Therapeutic use of
radionuclides includes 131I for
thyroid cancer and
hyperthyroid Graves' disease, 89SrCl3 for metastatic bone
tumors, 131I-MIBG for malignant
pheochromocytoma and
neuroblastoma, and
radioimmunotherapies. 131I is concentrated in 60-70% of
metastases from differentiated
thyroid cancer following total
thyroidectomy. Radioiodine uptake in metastatic lesions is greater in younger patients than in older ones.
Hypothyroidism is often mild or even absent in patients with a large amount of
tumor tissue, indicating that
thyroid hormones produced by highly differentiated
tumors compensate partially or even completely for
hypothyroidism following total
thyroidectomy. Adequate uptake of 131I has been reported to be associated with significant reduction in the size and number of
metastases, and with lower recurrence and higher survival rates. Other favorable factors for longer survival are younger age, well-differentiated histological type, small disease extent, and early discovery of
metastases. Older patients with extensive
metastases and/or bulky
tumor masses in the bone have a poor prognosis. Therefore, it is important to discover
metastases as early as possible, when patients are still young. Long-term follow-up with periodic
thyroglobulin measurements and imaging studies is strongly recommended. In Japan, 131I treatment for
Graves' disease is performed only in selected patients in whom
antithyroid drugs cannot be used because of side effects or not effective, considering the high prevalence of permanent
hypothyroidism. 89SrCl3 is useful for reducing
pain due to bone
metastases of malignant
tumors. 131I-MIBG
therapy is effective for improvement of QOL in some patients with metastatic malignant
pheochromocytoma. Radioimmuno-
therapy using anti-CD20 has been used successfully in clinical application in patients with malignant
B cell lymphoma.