The assessment of breast cancer (BC) response to neoadjuvant therapy: A SPECT/CT study

Objectives To evaluate the usefulness of SPECT/CT in the assessment of BC response to neoadjuvant therapy.

Methods 39 consecutive BC patients (33-82 yrs) scheduled to neoadjuvant chemo (29 cases) or hormonal (10 cases) therapy underwent 99mTc-tetrofosmin SPECT/CT before and after therapy using a dual head gamma camera integrated with an X-ray tube for low dose CT, including both breasts and axillae in the field of view.All 39 patients had breast surgery with associated axillary lymph node dissection in 34/39 cases.

Results In the post-therapy study SPECT/CT was negative in 6/6 completely responder patients (specificity: 100%) and positive in 29/33 patients with residual tumors (sensitivity: 87.9%). The residues were macroscopic (1.2-7 cm) in 27/29 positive cases and microscopic in 2/29. A high correlation between tumor uptake and tumor extension found at surgery was observed in all 29 positive cases, with also precise tumor localization. SPECT/CT missed residual disease in the remaining 4 patients who had microscopic residues scattered in a fibrotic area in 2 cases and macroscopic residues (a mucinous BC and a multifocal lobular BC, respectively) in the other 2 cases. Moreover, SPECT/CT detected axillary lymph node metastases in 11/23 affected patients (sensitivity: 47.8%) and it was false negative in l2 patients with lymph nodes with post-chemotherapy fibrotic changes and small deposits of metastases. No axillary false positive findings were observed (specificity: 100%).

Conclusions 99mTc-tetrofosmin SPECT/CT appears a useful diagnostic tool in the assessment of BC response to neoadjuvant therapy. A positive study, either in the breast or in the axilla, is highly predictive of residual disease, while a negative study cannot exclude it, especially when microscopic.