[Clinical significance of whole body thallium-201 chloride scintigraphy in multiple myeloma]

This study attempts to characterize the findings of thallium-201 chloride (201TlCl) uptake in patients with multiple myeloma and to evaluate its clinical significance. Twenty-four patients (including 10 untreated cases, 5 relapsed cases and 9 cases in stable course after initial treatment) were evaluated. Whole body 201Tl scintigraphy was performed 10 minutes after intravenous administration of 111 MBq of 201TlCl. Abnormal scintigraphic findings in whole body scanning varied from solitary focal uptake to extensive diffuse bone marrow visualization, but fell into the following 3 broad types; 1) skeletal visualization type, 2) predominant focal uptake type and 3) mixed type. Diffuse bone marrow uptake could be classified according to the skeletal distribution into 5 gradings (grade 0-4) between normal and entire skeletal visualization. This grading was roughly related to estimated tumor mass classification by tumor mass staging system (Alexanian, 1985). Furthermore, serum beta2-microglobulin level, that is widely confirmed as the reliable parameter of tumor burden and response to treatment except for patients with renal dysfunction, showed significant difference between grade 2 and grade 3 (p < 0.05), grade 2 and grade 4 (p < 0.01). The detectability of focal myelomatous lesions was compared to those of plain radiographs and 99mTc-HMDP scintigraphy in the untreated cases. Whole body 201Tl scintigraphy demonstrated 32 lesions among 46 focal lesions which included lesions revealed on either X-ray CT or MR imaging. In contrast to whole body 201Tl scintigraphy, plain radiographs and 99mTc-HMDP scintigraphy demonstrated 23 lesions and 22 lesions, respectively. All focal lesions exceeding 5 cm3 in tumor size were detectable on whole body 201Tl scintigraphy. Whole body 201Tl scintigraphy additionally showed 12 focal lesions that were demonstrated on MR imagings but failed to be detected on plain radiographs. However, detection of small lesions confined within the vertebral body was difficult. In conclusion, whole body 201Tl scintigraphy is a useful non-invasive tool to investigate the patients with multiple myeloma.