BACKGROUND: We assessed the validity of ^99mTc-MIBI scintigraphy and MRI in the diagnosis and prediction of the effect of therapy in patients with multiple myeloma (MM) and monoclonal gammopathy of unknown significance (MGUS), in whom both examinations were performed within 14 days.
MATERIAL AND METHODS: Forty-seven consecutive patients with MM and 5 with MGUS were enrolled in the study. Out of 47 MM patients, 6 were in Durie-Salmon stage I and 41 had active disease in stage II or III. Fifteen patients were examined before and within 2 months of intensive chemotherapy. Anterior and posterior whole-body scans were obtained 10 min after IV administration of 740 MBq (20 mCi) ^99mTc-MIBI. MRI of Th and LS spine, T1 w.i. and STIR in the sagittal plane were performed.
RESULTS: Bone marrow pathological changes in 41 MM patients with active disease were detected in 39 (95%) scintigraphic examinations and in 38 (94%) of MRI. Among 41 MM patients with active disease, 21 showed diffuse patterns of ^99mTc-MIBI uptake, 8 showed focal patterns and 10 showed both focal and diffuse patterns, while 34 patients exhibited focal lesions in MRI and 4 both focal and diffuse findings. Moreover, 5 of 38 patients had epidural mass and 18 had vertebrae compression. Out of 15 patients after therapy, 13 reached complete remission and 2 had stable disease. Normal ^99mTc-MIBI scintigraphy was found in 11 (85%) patients with complete remission, 2 presented both focal and diffuse patterns of ^99mTc-MIBI uptake. Two patients with stable disease also had focal and diffuse radiotracer uptake. MRI findings were normal only in 3 (23%) patients in complete remission. Eight patients exhibited focal lesions and 2 showed partial conversion in MRI.
CONCLUSIONS: ^99mTc-MIBI scintigraphy and MRI are methods of equal sensitivity in detecting active MM and complement each other. The advantage of 99mTc-MIBI scintigraphy is the possibility of whole body examination, which allows superiority in detection of MM in appendicular skeleton and extramedular lesions, and faster response to therapy, while the advantage of MRI is the detection of epidural masses and vertebral compressions influencing the therapeutic strategy.