Breast cancer: treatment response assessment with FDG-PET/CT in the neoadjuvant and in the metastatic setting

PurposeVarious treatment options are available for breast cancer in the neoadjuvant and in the metastatic setting. Early and accurate assessment can support treatment adaptation. This review aims to clarify the potential role of FDG-PET/CT to assess treatment response in breast cancer patients.MethodsWe performed a comprehensive literature review and assessment of research studies with the keywords "treatment response", "breast cancer" and "FDG-PET/CT".ResultsOf 589 references analyzed, 138 were kept in the final analysis. FDG-PET/CT could early evaluate the response to neoadjuvant treatment in breast cancer (with better sensitivity than specificity) but the evaluation methods differ between studies. Taking into account the primary tumor phenotype and the type of treatment can help to better homogenize the evaluation criteria. Taking into account tumor phenotype, FDG-PET/CT is promising to assess neoadjuvant treatment response early in triple-negative and in HER2-positive tumors. At the end of neoadjuvant treatment, FDG-PET/CT tends to underestimate residual disease. FDG-PET/CT is effective for evaluating systemic treatments in the metastatic setting. By providing both functional and morphological information, FDG-PET/CT is more useful than CT alone or than bone scintigraphy for assessing treatment response of bone metastases.ConclusionFDG-PET/CT may be offered for the early assessment of response to neoadjuvant therapy, particularly in triple-negative or HER2-positive tumors, but treatment modification on the basis of FDG-PET/CT is not currently recommended outside clinical studies. FDG-PET/CT may play an important role in monitoring treatment response in the metastatic setting (especially in bone metastases) and FDG-PET/CT is more helpful than conventional imaging (CE-CT and bone scan).