**4. Radionuclide therapy of skeletal tumors**

Metastatic bone cancer is a common complication of malignant tumor. It is reported that 20%-75% of cancer patients has developed bone metastases according to necropsy results. Malignant bone pain is still a challenging clinical problem. Pain due to bone metastases will greatly decrease the patient's quality-of-life because of patient's gradual deterioration, local body dysfunction, and mental and physical collapse. Recently, there are several reports on therapy of painful bone metastases by radiotherapy or anticancer drugs showing therapeutic efficacy. The studies, however, were generally heterogeneous trials involving stage of diagnosis, radiopharmaceuticals dosage, combination with other therapeutic modalities and methods of pain assessment. In addition, there are few reports on the study of comparison of radionuclide therapy with chemotherapy for evaluating the therapeutic effectiveness of the patients with painful bone metastases.

### **4.1 Radionuclide internal-radiation therapy**

Radionuclide internal-radiation therapy of severe bone pain due to multiple skeletal metastases has recently achieved successful stage in nuclear medicine, which has been much considered and widespread used. In this chapter we described the principle of treatment of painful disseminated skeletal metastases, therapeutic approaches, evaluation of effective treatment according to our clinical experience in routine clinical treatment and its future applications.

89Sr-chloride (Metastron) has been approved by the FDA for relief of bone pain in cases of painful skeletal metastases. The compound behaves biologically like calcium and localizes in hydroxyapatite crystal by ion exchange. Strontium uptake occurs preferentially at sites of active osteogenesis. This allows primary bone tumors and areas of metastatic involvement to accumulate significantly higher concentrations of strontium than surrounding normal bone. 89Sr decays by beta- emission with a half life of 50.6 days. The conventional dose of 89Sr-chloride is 148 MBq (4mCi), and can be reinjection after three months if necessary. Before administration, a blood regulation test should be checked.

Another two radiotherapeutic agents, 186Re-HEDP and 153Sm-EDTMP are also used in the area. 186Re decays by beta- and gamma emission with a half life of 90.6 hr and 153Sm decays by beta- emission and has a half life of 46.3 hr. Both of these beta-emitting radionuclides are complex with bone-seeking ligands, which localize by chemisorption. The duration of

Skeleton System 303

a b c

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iamging: c: sagittal slice imaging)

**6. Conclusion** 

nuclear medicine.

**7. References** 

Fig. 14 Normal image of 18F- Fluoride PET(a: 3D projection imaging b: coronal slice

It is important to resolve the problems on skeletal and soft tissue tumors for clinicians to seek for new diagnostic and therapeutic radiopharmaceuticals. Although rapid developments of medical science and great progress have been made recently, there are still some limitations. The clinical applications of radionuclide tracing technique in diagnosis and treatment of skeletal and soft tissue tumor is attached importance to clinical physicians with widely using the technique in clinical routine practice and continuing development of

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metastases in patients with breast cancer: comparison with 99mTc-MDP bone

response is 1-12 months. The main toxicity of these radiotherapeutics is mild transient bone marrow suppression.
