Diffusion-weighted and Dynamic Contrast-enhanced MRI of Metastatic Bone Tumors: Correlation of the Apparent Diffusion Coefficient, K(trans) and ve values

PURPOSE: To investigate whether quantitative parameters derived from Diffusion-weighted magnetic resonance imaging (DW-MRI) correlate with those of Dynamic contrast-enhanced MRI (DCE-MRI). MATERIALS AND METHODS: Thirteen patients with pathologically or clinically proven bony metastasis who had undergone MRI prior to treatment were included. The voxel size was 1.367 x 1.367 x 5 mm. A dominant tumor was selected and the apparent diffusion coefficient (ADC) value and DCE-MRI parameters were obtained by matching voxels. DCE-MRI data were analyzed yielding estimates of K(trans) (volume transfer constant) and ve. (extravascular extracellular volume fraction). Statistical analysis of ADC, K(trans), and ve value was conducted using Pearson correlation analyses. RESULTS: Fifteen lesions in pelvic bones were evaluated. Of these, 11 showed a statistically significant correlation (P < 0.05) between ADC and K(trans). The ADC and K(trans) were inversely related in 7 lesions and positively related in 4 lesions. This did not depend on the primary cancer or site of metastasis. The ADC and ve of 9 lesions correlated significantly. Of these, 4 lesions were inversely related and 5 lesions were positively related. CONCLUSION: Unlike our theoretic hypothesis, there was no consistent correlation between ADC values and K(trans) or between ADC values and ve in metastatic bone tumors.

Enhanced expression of cathepsin L in metastatic bone tumors

Cathepsin L is a kind of cystein proteases which are known to facilitate the invasion and metastasis of tumor cells by degrading the components of basement membrane and extracellular matrix. This study was undertaken to investigate the expression of cathepsin L by Northern blot analysis with radiolabeled cDNA specific for cathepsin L in six normal tissues, two osteosarcoma cell lines, MG-63 and Saos-2, six primary bone tumors and six metastatic bone tumors. In six normal tissues, the highest level of cathepsin L was expressed in liver with the descending order of liver > lung > thymus > ovary > kidney > esophagus. One of the two osteosarcoma cell lines established from the primary sites expressed a high level of cathepsin L mRNA. Out of six primary bone tumors, three (50%) expressed cathepsin L mRNA, while all (100%) of six metastatic bone tumors expressed the mRNA. These results demonstrating the higher frequency of expression of cathepsin L in metastatic bone tumors suggest that cathepsin L may participate in tumor invasion and metastasis.