Metabolic activity in bone metastases of breast and prostate cancer were similar as studied by 18F-FDG PET/CT. The role of 99mTc-MDP.

OBJECTIVE The aim of this study was to compare the metabolic activity of metastatic foci from breast and prostate cancer patients as scanned by fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) and by technetium-99m methyl diphosphonate (99mTc-MDP) bone scan (BS). SUBJECTS AND METHODS Forty one patients were studied, divided into 2 groups based on histologically confirmed diagnosis: a) Breast cancer group, 23 women, mean age: 61±12 years, range: 37-79 years and, b) Prostate cancer group, 18 men, mean age 68±8 years, range: 52-82 years. Another group of 17 non cancer atherosclerotic subjects 9 women and 8 men, of mean age and age range similar to the above were also studied for comparison. The R index (the total count rate in bone metastases divided by the total count rate in a contralateral area), the maximum semi-quantitative standardized uptake value (SUVmax) of BS lesions and the mean number of metastases were evaluated. For the metastatic findings in the PET/CT scans the automatic method of contouring with 50% background cut-off was used, while for the 99mTc-MDP BS metastases were delineated manually. RESULTS The mean R index of the bone metastatic foci studied by 18F-FDG PET/CT was 1.89±0.69 for Groups I and II patients. There was no significant difference of the R index between prostate cancer and breast cancer metastases (1.95±0.86 vs 1.83±0.52). The average SUVmax value was significantly higher in breast cancer patients than in prostate cancer patients (5.15±2.54 vs 4.01±1.71; P<0.05). There was no significant correlation in both cancer groups between R index and SUVmax values. The number of metastatic foci diagnosed by the 99mTc-MDP BS scan was much less than by the 18F-FDG PET/CT. CONCLUSION No significant correlation was noticed in the metabolic activity-glucose utilization of metastatic bone foci between breast and prostate cancer cases. This observation validates the independent value of analyzed diagnostic methods and suggests negligible influence of glucose utilization in bone re-modeling in the above metastatic cancer cells. The 18F-FDG PET/CT bone scan was much better in diagnosing metastases compared to the 99mTc-MDP scan.