For assessment of the primary breast tumor, one prospective study of 51 stage II and III breast cancer patients reported that MRI and DBT outperformed mammography and whole-breast US in the prediction of pathologic complete response [113]. However, this study cannot be extrapolated to axillary nodal disease. FDG-PET/CT Skull Base to Mid-Thigh There are limited data to support the use of FDG-PET/CT for assessing response of nodal disease from breast cancer following completion of NAC. Most studies report changes in size and SUV measurements of the index breast carcinoma or distant metastases. Four meta-analyses of FDG-PET/CT in detecting residual breast disease reported a pooled sensitivity of 81% to 84% and a specificity of 66% to 79% [114-118]. FDG-PET/CT is limited by the lack of consensus for standard criteria to measure response of the index tumor or nodal disease, and SUV measurements underestimating the amount of residual disease when the residual tumor size is small. In one meta-analysis, 4 of 19 studies reported a pooled sensitivity of 92% and an NPV of 88% in predicting regional lymph node response but the specificity was inconclusive [118]. Even though there is suggestion that the early changes in SUV may correlate Imaging of the Axilla with NAC response, a negative FDG-PET/CT does not guarantee that the final pathology is also negative, especially if the residual tumor is of low to moderate grade [119,120]. A recent report from the National Cancer Database of 33,162 patients concluded that a breast-only response from a node-only response or both breast and nodal response had different prognoses, which also varied with tumor subtypes [112]. Given the limited data, FDG-PET/CT is not currently performed post-NAC to restage the axilla. Mammography Diagnostic Mammography can reliably be used to assess response of a primary breast malignancy to NAC. However, it is less useful in assessing axillary nodal response to therapy given that the axilla is incompletely visualized.
Imaging of the Axilla. For assessment of the primary breast tumor, one prospective study of 51 stage II and III breast cancer patients reported that MRI and DBT outperformed mammography and whole-breast US in the prediction of pathologic complete response [113]. However, this study cannot be extrapolated to axillary nodal disease. FDG-PET/CT Skull Base to Mid-Thigh There are limited data to support the use of FDG-PET/CT for assessing response of nodal disease from breast cancer following completion of NAC. Most studies report changes in size and SUV measurements of the index breast carcinoma or distant metastases. Four meta-analyses of FDG-PET/CT in detecting residual breast disease reported a pooled sensitivity of 81% to 84% and a specificity of 66% to 79% [114-118]. FDG-PET/CT is limited by the lack of consensus for standard criteria to measure response of the index tumor or nodal disease, and SUV measurements underestimating the amount of residual disease when the residual tumor size is small. In one meta-analysis, 4 of 19 studies reported a pooled sensitivity of 92% and an NPV of 88% in predicting regional lymph node response but the specificity was inconclusive [118]. Even though there is suggestion that the early changes in SUV may correlate Imaging of the Axilla with NAC response, a negative FDG-PET/CT does not guarantee that the final pathology is also negative, especially if the residual tumor is of low to moderate grade [119,120]. A recent report from the National Cancer Database of 33,162 patients concluded that a breast-only response from a node-only response or both breast and nodal response had different prognoses, which also varied with tumor subtypes [112]. Given the limited data, FDG-PET/CT is not currently performed post-NAC to restage the axilla. Mammography Diagnostic Mammography can reliably be used to assess response of a primary breast malignancy to NAC. However, it is less useful in assessing axillary nodal response to therapy given that the axilla is incompletely visualized.