The usefulness of Tc-99m-tetrofosmin SPECT/CT in the detection of residual tumors and axillary lymph node metastases in breast cancer patients following neoadjuvant therapy.

Single photon emission computed tomography (SPECT)/CT is emerging as a useful diagnostic tool in several oncological fields. In this prospective study, we assessed the usefulness of Tc-99m-tetrofosmin SPECT/CT in the detection of both residual breast tumors and axillary lymph node metastases following neoadjuvant therapy. Thirty-seven consecutive breast cancer patients scheduled to surgery following neoadjuvant therapy preoperatively underwent a Tc-99m-tetrofosmin SPECT/CT study, using a dual head gamma camera integrated with a x-ray tube for low-dose CT, including both breasts and axillary regions in the field of view. Within 1 week of SPECT/CT, all 37 patients had breast surgery with associated axillary lymph node dissection in 33/37 cases. At surgery, 31/37 patients had breast residues (microscopic in 4/31 cases and macroscopic in 27/31 cases). Axillary lymph node metastases were ascertained in 19/33 cases (N1mi: 2 cases, N1a: 8 cases, N2a: 6 cases, N2b: 3 cases). SPECT/CT sensitivity, specificity, and accuracy in detecting residual tumors were 87%, 100%, and 89.2%, respectively; the corresponding values in detecting axillary lymph node metastases were 36.8%, 92.8%, and 60.6%. SPECT/CT missed breast cancer residues in 4/31 patients, including 2 cases with microscopic residual disease. Moreover, lymph node metastases were missed in 12/19 patients (10/12 with pN1mi or pN1a metastases), all with lymph nodes with post-therapy fibrotic changes and small deposits of metastases. Tc-99m-tetrofosmin SPECT/CT proved a useful diagnostic tool in the detection and in the localization of residual breast tumors following neoadjuvant therapy. The procedure lacked in sensitivity in identifying axillary lymph node metastases, especially in patients with a limited lymph node involvement. According to our data, SPECT/CT may guide the surgeon to the most appropriate breast surgical treatment and to eventually select the most suitable axillary lymph node sampling (axillary lymph node dissection or sentinel node biopsy).