A U.S. Food and Drug Administration (FDA) pooled analysis of outcomes for bone only metastatic breast cancer (MBC).

570Background: Although bone involvement is common in MBC, little is known about the subset of patients with bone only (BO) disease and difficulties surround the radiographic assessment of bone metastases. Methods: Data was analyzed from eleven prospective studies (n = 7950) of nine experimental agents submitted for treatment of MBC in initial or supplemental New Drug or Biologics License Applications since 2005. Analyses were performed in three subsets: BO, bone with other metastases (BWO), and no bone metastases (NBO). Early discordance rate (EDR; investigator calls progression event earlier than blinded independent central review {BICR}) and late discordance rate (LDR; investigator calls progression event later than BICR) were estimated on 4012 patients subject to a BICR. Results: Bone metastases were identified in 35-57% of patients across studies. BO disease was present in 4-26% of patients, dependent on subtype. EDR for patients with lesions outside the bone (n = 3691) was 40%, and LDR was 45%. For ...