A Prospective Study of Bone Tumor Response Assessment in Metastatic Breast Cancer

Background: In our previous study, new MD Anderson (MDA) bone tumor response criteria (based on computed tomography [CT], plain radiography [XR], and skeletal scintigraphy [SS]) predicted progression-free survival (PFS) better than did World Health Organization (WHO) bone tumor response criteria (plain radiography [XR] and SS) among patients with breast cancer and bone-only metastases. In this pilot study, we tested whether MDA criteria could reveal bone metastasis response earlier than WHO criteria in patients with newly diagnosed breast cancer with osseous and measurable nonosseous metastases. Methods: We prospectively analyzed bone metastasis response using each imaging modality and set of bone response criteria to distinguish progressive disease (PD) from non-PD and their association with PFS and overall survival (OS). We also compared the response of osseous metastases assessed by both criteria with the response of nonosseous measurable lesions. Results: The median follow-up period was 26.7 months (range, 6.1-53.3 months) in 29 patients. PFS rates differed at 6 months based on the classification of PD or non-PD using either set of criteria (MDA, P =.002; WHO, P =.014), but these rates, as well as OS, did not differ at 3 months. Response in osseous metastases by either set of criteria did not correlate with the response in nonosseous metastases. Conclusion: MDA and WHO criteria predicted PFS of patients with osseous metastases at 6 months but not at an earlier time point. We plan a well-powered study to determine the role of MDA criteria in predicting bone tumor response by incorporating 18-fluorodeoxyglucose (¹⁸F) positron emission tomography (FDG-PET)/CT to see if findings using this modality are earlier than those with WHO criteria.