Evaluation of radiographic and metabolic changes in bone metastases in response to systemic therapy with 18FDG-PET/CT

Abstract

Purpose: The aim of this study was to retrospectively evaluate radiographic and metabolic changes in bone metastases in response to systemic therapy with ¹⁸FDG-PET/CT and determine their roles on the evaluation of therapy response.

Materials and Methods: We retrospectively evaluated radiographic and metabolic characteristics of bone metastases in 30 patients who were referred for the evaluation of response to systemic therapy with ¹⁸FDG-PET/CT.  All patients underwent integrated ¹⁸FDG-PET/CT before and after treatment.

Results: Responders group: The baseline radiographic patterns of the target lesions were lytic, sclerotic, mixed and  CT negative; after treatment the radiographic patterns of all target lesions changed to a sclerotic pattern and attenuation increased (p=0.012) and metabolic activity decreased (p=0.012). A correlation was found between decreasing metabolic activity and increasing attenuation of the target lesions (r=-0.55) (p=0.026).  Non-responders group: The baseline radiologic patterns of the target lesions were lytic, blastic , mixed and CT negative; after treatment all lytic target lesions remained the same and one CT negative lesion turned to lytic pattern and the attenuation of the target lesions decreased (p=0.12) and metabolic activity increased  (p=0.012). A correlation was found between increasing metabolic activity and decreasing attenuation (r=-0.65) (p=0.032). An exception of this rule was seen in baseline blastic metastases which progressed with increasing in size, metabolic activity and attenuation

Conclusion: This study shows that the metabolic activity of lesions is a more reliable parameter than the radiographic patterns for the evaluation of therapy response.