We aim to investigate the value of 3'-deoxy-3'-18F-fluorothymidine (18F-FLT) and 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) for early prediction of treatment response and survival in patients with metastatic breast cancer after salvage therapy.

Patients with metastatic breast cancer were enrolled and received PET/CT using 18F-FLT and 18F-FDG at baseline, after 1st cycle , and after 2nd cycle of systemic chemotherapy. The standard reference for treatment response was classified according to Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria for contrast-enhanced CT (CE-CT) after 3 months of systemic chemotherapy. The metabolic response on PET was assessed according to PET response criteria in solid tumors (PERCIST) criteria and was correlated to the treatment response, progression-free survival (PFS), and overall survival (OS).

Inclusion Criteria:

• Participants must have histological evidence of breast cancer of any stage
• Participants must be diagnosed with metastatic breast cancer
• Participants should be willing and able to have both PET-CT scans
• Participants should be eligible for and plan to undergo systemic chemotherapy and should be seen by a oncologist prior to beginning the study
• Participants should have the ability to understand and the willingness to sign a written informed consent document
• Participants must sign a study specific consent form prior to registration

Exclusion Criteria:

• Patients have been diagnosed with other malignancy
• Patients with uncontrolled intercurrent illness including, but not limited to, ongoing or active infection or significant inflammation at treatment site or psychiatric illness/social situations that would limit compliance with study requirements or whose lab values do not meet the criteria above are excluded
• Pregnant women are excluded from this study
• Breast feeding women are excluded from this study