Diagnosis and evaluation of therapeutic response of bone metastases

Abstract: The aim of this study was to investigate different aspects of different imaging modalities in the diagnosis of bone metastases and in the assessment of their response to therapy.The role of CT, with and without clinical information, was investigated as compared to CT-guided bone biopsy in the evaluation of suspected bone metastases. The diagnostic accuracy of CT alone (44%) increased to 82% when clinical information was taken into account, especially for the lesions diagnosed histopathologically as benign. In most cases, CT in combination with clinical information gave enough information about the nature (malignant or benign) of a bone lesion. In uncertain cases the diagnostic accuracy could be improved by means of CT-guided bone biopsy.Possible misinterpretation of new sclerotic lesions when judged according to the WHO criteria during treatment was studied. One hundred and thirty-nine breast cancer patients with bone metastases, who participated a the clinical trial of clodronate therapy, were studied retrospectively. In 8 of the 24 patients considered at conventional radiography to have progressive disease according to WHO criteria, 17 of 52 apparently new sclerotic lesions (33%) were detected on previous bone scintigraphy. WHO criteria may give rice to misinterpretations in patients with new sclerotic lesions. For better assessment more sensitive techniques, e.g. bone scintigraphy, can be used as a complement to conventional radiography.Eighteen breast cancer patients with known bone metastases were studied prospectively regarding evaluation of therapy response. T1-weighted spin echo (SE) and fat-suppressed long echo time inversion recovery turbo spin echo (long TE IR-TSE) MR sequences, conventional radiography, bone scintigraphy and CT-guided bone biopsy were performed before and during systemic chemotherapy. T1-weighted sequences and long TE IR-TSE sequences were compared regarding evaluation of early response of breast cancer bone metastases to chemotherapy, using a combination of clinical, radiographic and scintigraphic examinations as a reference. Therapeutic response evaluation with MR imaging was based on change in tumor size assessed quantitatively by measuring all focal metastases, and on change in pattern and signal intensity (SI) of the metastases, assessed visually. The long TE IR-TSE sequence demonstrated partial response of breast cancer bone metastases to chemotherapy more accurately than the T1-weighted sequence (58% vs. 17%).The effect of granulocyte colony-stimulating factor (G-CSF)-supported chemotherapy on MR images of normal red bone marrow was investigated. A diffuse, homogeneous SI increase was observed visually and quantitatively in initially normal bone marrow during G-CSF therapy, obscuring some focal lesions. No such SI change was visible after G-CSF therapy or in patients not receiving G-CSF. We concluded that G-CSF-supported chemotherapy might induce diffuse SI changes in normal red bone marrow on MRI, and that this might lead to misinterpretations in the evaluation of response of bone metastases.Early response of bone metastases to therapy was assessed in targeted metastatic lesions in breast cancer patients with T1-weighted and long TE IR-TSE MR sequences and CT compared with histopathological findings. The results indicated that the SI increase in the metastatic lesions following therapy on long TE IR-TSE images might be useful in indicating an early response. T1-weighted images are of limited value in assessing alterations in the amount of tumor cells. An increase in electron density on CT can be seen in both responding and progressing lesions.