Assessment of Bone Lesions with 18F-FDG PET Compared with 99mTc Bone Scintigraphy Leads to Clinically Relevant Differences in Metastatic Breast Cancer Management.

It is unknown whether assessment of potential bone lesions in metastatic breast cancer (MBC) by 18F-FDG PET instead of 99mTc bone scintigraphy (BS) supports clinically relevant changes in MBC management. Therefore, we retrospectively compared management recommendations based on bone lesion assessment by 18F-FDG PET plus contrast-enhanced CT (ceCT) or BS plus ceCT, for patients with newly diagnosed MBC. Methods: Baseline ceCT, BS, and 18F-FDG PET for all patients included in the IMPACT-MBC study (NCT01957332) at the University Medical Center Groningen were reviewed for bone lesions. If bone lesions were found by any imaging modality, virtual MBC management recommendations were made by a multidisciplinary expert panel, based on either 18F-FDG PET plus ceCT or BS plus ceCT. The panel had access to standard clinicopathologic information and baseline imaging findings outside the skeleton. Clinically relevant management differences between the 2 recommendations were defined either as different treatment intent (curative, noncurative, or unable to determine) or as different systemic or local treatment. If no bone lesions were found by any imaging modality, the patients were included in the analyses without expert review. Results: In total, 3,473 unequivocal bone lesions were identified in 102 evaluated patients (39% by ceCT, 26% by BS, and 87% by 18F-FDG PET). Additional bone lesions on 18F-FDG PET plus ceCT compared with BS plus ceCT led to change in MBC management recommendations in 16% of patients (95% CI, 10%-24%). BS also changed management compared with 18F-FDG PET in 1 patient (1%; 95% CI, 0%-5%). In 26% (95% CI, 19%-36%) of patients, an additional 18F-FDG PET exam was requested, because BS provided insufficient information. Conclusion: In this exploratory analysis of newly diagnosed MBC patients, 18F-FDG PET versus BS to assess bone lesions resulted in clinically relevant management differences in 16% of patients. BS delivered insufficient information in over one fourth of patients, resulting in an additional request for 18F-FDG PET. On the basis of these data, 18F-FDG PET should be considered a primary imaging modality for assessment of bone lesions in newly diagnosed MBC.