[18F-FDG PET/CT and 99mTc-MIBI scintigraphy in evaluation of patients with multiple myeloma and monoclonal gammopathy of unknown significance: comparison of methods].

BACKGROUNDS

Newer imaging modalities, such as 18F-FDG PET/CT and 99mTc-MIBI scintigraphy, have been recently introduced to assess the activity and extent of disease in patients with multiple myeloma (MM) and gammopathy of undetermined significance (MGUS). The aim of our study was to compare the impact of these imaging modalities in the evaluation of MM and MGUS patients.

MATERIALS AND METHODS

A total of 101 patients with MM (81 patients) and MGUS (20 patients) were enrolled in the study (21 newly diagnosed and 44 relapsed patients with symptomatic MM, 16 with asymptomatic MM and 20 with MGUS). All patients were without therapy and underwent 18F-FDG PET/CT and 99mTc-MIBI scintigraphy within a maximum interval of 14 days. The scans were classified as normal (N), diffuse (D), and focal or combined (F-FD) pattern.

RESULTS

There was no significant difference in the detection of newly diagnosed MM and relapsed patients between the compared methods. 18F-FDG PET/CT performed better than 99mTc-MIBI scintigraphy in the detection of focal lesions (p < 0.039), whereas 99mTc-MIBI scintigraphy was superior in the visualization of diffuse disease (p = 0.042). 18F-FDG PET/CT visualised significantly more focal lesions than 99mTc-MIBI scintigraphy (p = 0.002), both generally in the cohort and when comparing the number of focal lesions per patient. Both the imaging modalities singly or in combination influenced the subsequent clinical management in 17% of patients. In our study, 18F-FDG PET/CT predicted asymptomatic MM and MGUS transformation into more aggressive forms with the necessity to start therapy more often than 99mTc-MIBI scintigraphy.

CONCLUSION

18F-FDG PET/CT appeared to be a better imaging technique than 99mTc-MIBI scintigraphy in the detection of focal lesions in patients with symptomatic MM. 99mTc-MIBI was superior in the visualization of diffuse disease. On the other hand, despite its limited capacity in detecting focal lesions, 99mTc-MIBI scintigraphy still remains the most rapid and inexpensive technique for whole-body evaluation and may be an alternative option when a PET/CT facility is not available.