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Abstract. In a previous study, we showed the ability of technetium-99m methoxyisobutylisonitrile ([sup 99m]Tc-MIBI) scan to identify active disease in patients with multiple myeloma (Eur J Nucl Med 1998; 25: 714-720). In particular, a semiquantitative score of the extension and intensity of bone marrow uptake was derived and correlated with both the clinical status of the disease and plasma cell bone marrow infiltration. In order to estimate quantitatively [sup 99m]Tc-MIBI bone marrow uptake and to verify the intracellular localization of the tracer, bone marrow samples obtained from 24 multiple myeloma patients, three patients with monoclonal gammopathy of undetermined significance (MGUS) and two healthy donors were studied for in vitro uptake. After centrifugation over Ficoll-Hypaque gradient, cell suspensions were incubated with [sup 99m]Tc-MIBI and the uptake was expressed as the percentage of radioactivity specifically retained within the cells. The cellular localization of the tracer was assessed by micro-autoradiography. Twenty-two out of 27 patients underwent [sup 99m]Tc-MIBI scan within a week of bone marrow sampling. Whole-body images were obtained 10 min alter intravenous injection of 555 MBq of the tracer; the extension and intensity of [sup 99m]Tc-MIBI uptake were graded using the semiquantitative score. A... [ABSTRACT FROM AUTHOR]

Technetium-99m 2-methoxyisobutylisonitrile (99mTc-MIBI or setamibi) has recently been proposed for use in the evaluation of multiple myeloma (MM). The aims of this study were to investigate its potential predictive value in patients with MM and its possible role in the follow-up. Thirty patients with MM who had undergone two 99mTc-MIBI scintigraphic studies at least 2 months apart constituted the study group; 22 of them received chemotherapy in the interval between the two scans. The scans were classified as showing pattern N when only physiological uptake was present, pattern D when diffuse bone marrow uptake was observed, pattern F when areas of focal uptake of the tracer were evident, and pattern F + D when both D and F patterns were observed. Comparative 99mTc-MIBI scintigraphy was considered indicative of disease progression when there was a worsening of the pattern (i.e. from N to D, or from N or D to F or to F + D) or an increase in the pattern D semiquantitative score. It was considered indicative of disease improvement when the opposite trend was observed; otherwise, it was considered to document a stable condition. A significant association was observed between the baseline scintigraphic pattern and clinical status at follow-up in the group of patients evaluated after chemotherapy (chi 2 = 16.7, P < 0.05). A negative baseline 99mTc-MIBI scintigram showed a high predictive accuracy (100%) for remission, while the presence of pattern F or F + D was often associated with a less favourable outcome. A multivariate analysis showed that 99mTc-MIBI uptake pattern has an added value in relation to known prognostic variables such as C-reactive protein. 99mTc-MIBI scintigraphy patterns at follow-up were significantly associated with the clinical status evaluated after chemotherapy (chi 2 = 32.6, P < 0.0001). Considering pattern N as indicating remission, pattern D stable condition, and pattern F or F + D progressive disease, a high concordance between scintigraphic findings and clinical status was found in the 22 patients undergoing chemotherapy (91%). Variation in 99mTc-MIBI findings comparing baseline and follow-up evaluations was significantly associated with clinical status both in patients undergoing chemotherapy (chi 2 = 26.5, P < 0.0005) and in those not undergoing chemotherapy (chi 2 = 8.0, P < 0.005). In conclusion, the results of this study suggest a prognostic value of 99mTc-MIBI scintigraphy in patients with MM and a potential role during the follow-up.

Technetium-99m 2-methoxyisobutylisonitrile (99mTc-MIBI) has been proposed as a potential tracer in patients with multiple myeloma (MM). The aims of this study were to evaluate the incidence of various patterns of diffuse 99mTc-MIBI uptake in patients with MM, to assess their relationship with clinical status and stage of disease, and to try to clarify the meaning of the diffuse bone marrow uptake of 99mTc-MIBI. Thirty-nine consecutive patients with MM were studied. Twenty-nine of these patients had active disease (13 in stage I, ten in stage II, and six in stage III) and ten were in remission after chemotherapy. Anterior and posterior whole-body scans were obtained 10 min after i.v. injection of 555 MBq of 99mTc-MIBI. The scans were classified as showing: pattern N, when only physiological uptake was present; pattern D, when diffuse bone marrow uptake was observed; pattern F, when areas of focal uptake of the radiotracer were evident; or pattern D+F, when both D and F patterns were observed. Diffuse bone marrow uptake was scored according to extension and intensity. Seven of the 39 patients (18%) showed pattern N, 18 (46%) pattern D, 2 (5%) pattern F, and 12 (31%) pattern D+F. Of the 32 patients with a positive 99mTc-MIBI scan (i.e. showing pattern D, F or D+F), 29 (91%) had active disease. Only three patients in remission showed pattern D, but with a very low bone marrow uptake score. Both extension and intensity of diffuse bone marrow uptake correlated with the amount of the monoclonal component and the percentage of bone marrow plasma cells. The distribution of the 99mTc-MIBI uptake patterns differed among patients in different stages of disease. Using as criteria for advanced stage the presence of either focal uptake (pattern F or D+F) or pattern D with a high score, high (90%) diagnostic accuracy was obtained. In conclusion, the patterns of 99mTc-MIBI uptake in patients with MM are related to both the clinical status and the stage of disease. The presence of focal uptake or of intense diffuse bone marrow uptake suggests that the patient has active and advanced stage disease, while a negative scan in a patient with MM clearly indicates remission.