Monitoring the response of patients with locally advanced breast carcinoma to neoadjuvant chemotherapy using [technetium 99m]-sestamibi scintimammography

BACKGROUND. Mammographic and physical examination assessments of the response of locally advanced breast carcinoma (LABC) to neoadjuvant therapy have been shown to be inaccurate. The authors studied the feasibility and accuracy of [technetium 99m]-sestamibi (MIBI) for monitoring the response of patients with LABC to neoadjuvant chemotherapy. METHODS. Patients receiving neoadjuvant chemotherapy for LABC underwent prone lateral scintimammography before therapy, after 2 months of therapy, and close to the completion of chemotherapy (presurgery) if chemotherapy continued for >3 months. Images were analyzed both qualitatively and quantitatively using the lesion-to- normal breast MIBI uptake ratio (L:N). Imaging results were compared with the clinical response and the pathologic response as determined from the posttherapy surgical specimen. RESULTS. A total of 32 patients (29 who were assessable for primary tumor response and 28 who were assessable for lymph node response) were included in the study. The mean change in the primary tumor L:N MIBI uptake ratio after 2 months of chemotherapy was -35% for clinical responders and +17% for nonresponders (P < 0.001). Patients achieving a pathologic primary tumor macroscopic complete response (CR) had a mean change in uptake on the presurgical scan of -58% versus -18% for patients with a partial response (P < 0.005). A decrease of ≥40% in the MIBI uptake ratio identified CRs with 100% sensitivity and 89% specificity. Pretherapy imaging predicted axillary lymph node metastases in 85% of patients ultimately found to have ≥1 positive lymph nodes at surgery, but was less accurate in identifying residual lymph node disease after therapy (55% sensitivity and 75% specificity). CONCLUSIONS. MIBI imaging accurately assessed the response to neoadjuvant chemotherapy in patients with LABC. Further studies are needed to determine the role of MIBI in this group of patients.