99mTc-MIBI in the assessment of response to chemotherapy and detection of recurrences in bone and soft tissue tumours of the extremities.

AIM: This prospective study is focused on the assessment of tumour response in a group of 28 bone sarcoma patients using (99m)Tc-MIBI scintigraphy.

METHODS: The quantitative changes in MIBI uptake before and after chemotherapy were measured and associated with the pathological evaluation of the degree of tumour necrosis. Besides this, another group of 40 patients with bone and soft tissue tumours was studied in order to evaluate the diagnostic efficacy of (99m)Tc-MIBI scintigraphy versus computed tomography (CT) and/or magnetic resonance imaging (MRI) in detecting the status of the disease and its recurrences. After injection of 555-740 MBq of (99m)Tc-MIBI, regional and whole body images were acquired at 20 and 60 min. The lesion/normal (L/N) uptake ratio was calculated in both early and delayed images and the washout rate (WR%) of (99m)Tc-MIBI was obtained. Following 3-4 courses of chemotherapy, bone tumours were assessed by comparing the uptake ratio in the viable tumours with the amount of necrotic processes described in the surgically removed specimens.

RESULTS: In the first group of patients the rate of tumour response to chemotherapy, calculated according to the percentage of necrosis and the (99m)Tc-MIBI uptake ratios, was as follows: complete response in 12 patients, partial response in 8 and no response in 8 patients. Linear regression analysis of quantitative changes in (99m)Tc-MIBI uptake (expressed as changes percent) and of (99m)Tc-MIBI uptake ratio showed a positive correlation (r=0.77), whereas it showed a negative correlation with the changes in the washout ratio (r=-0.32). In the second group of patients (40 patients) (99m)Tc-MIBI scintigraphy proved to be able to detect recurrences of bone and soft tissue tumours. The sensitivity, specificity and accuracy of (99m)Tc-MIBI scan versus CT and/or MRI were calculated and they resulted 93%, 95% and 92% versus 86%, 75% and 84%, respectively.

CONCLUSION: The application of (99m)Tc-MIBI scan in the management of patients treated with chemotherapy may allow an early identification of the non-responder patients and lead to a choice of different strategies (alternative chemotherapy or salvage surgery).