99mTc-MIBI scintigraphy in multiple myeloma (MM): Correlation with the International Staging System (ISS)

Abstract

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Objectives: 99mTc-sestamibi (MIBI) scintigraphy has proved to be useful in the evaluation of MM patients. In particular, a relationship has been demonstrated between scintigraphic patterns of 99mTc-MIBI uptake and both clinical status and stage. Combinations of prognostic factors were suggested for staging classification of myeloma patients. The new ISS was developed using univariate and multivariate analyses. Serum beta2-microglobulin (Sβ2M) and serum albumin (SA) were selected from the various potential prognostic factors both because of their statistical power in various models as well as the known wide availability of these two simple inexpensive laboratory tests.The purpose of this study was to assess the correlation between the 99mTc-MIBI scan and prognostic factors in MM patients according to the ISS.

Methods: Twenty-five MM patients were studied. Eighteen mCi (660 MBq) 99mTc-MIBI were injected intravenously in each patient and the scans were obtained 10 min post injection. The scans were classified as: Normal (N) [when only normal physiological uptake was present], Diffuse (D) [when diffuse bone marrow uptake was observed], Focal (F) [when areas of local uptake of the tracer were evident], Focal and Diffuse (F+D) [when both patterns were observed]. The scans were scored according to intensity (I) and extent (E) of the radiotracer uptake; a summed score (S) was calculated for each patient. Scintigraphic findings were correlated by simple linear regression analysis with ISS, Sβ2M, and SA.

Results: Of the 25 patients, 7 patients showed only a D pattern of 99mTc-MIBI uptake. F 99mTc-MIBI uptake was the only finding in 6 patients and F+D bone marrow uptake in 5 patients. Normal physiological uptake was present in 7 patients. Eighteen pts were stage I, 3 stage II and 4 stage III. The S was 2.28±2.2 for stage I and 5±0.58 for stage II and III (p<0.001). There was a positive correlation between scores and Sβ2M and an inverse correlation between scores and SA; statistically significant differences were found between E and S scores and Sβ2M, and SA levels. Statistically significant differences were also found in scores for those patients who died as against for those alive at the end of the follow –up period.

Conclusions: 99mTc-MIBI scan provides useful information in the detection of disease activity, well correlated with Sβ2M, SA and ISS staging system.