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Spanu A. 1, Tanda F. 2, Dettori G. 3, Manca A. 2, Chessa F. 1, Porcu A. 3, Falchi A. 1, Nuvoli S. 1, Madeddu G. 1
1 Department of Nuclear Medicine, University of Sassari, Sassari, Italy
2 Department of Histopathology, University of Sassari, Sassari, Italy
3 Department of Surgery, University of Sassari, Sassari, Italy
Aim. We evaluated the usefulness of 99mTc-tetrofosmin axillary pinhole (P)-SPECT in breast cancer (BC) non palpable axillary lymph node metastasis detection compared with conventional planar and SPECT scintimammography.
Methods. We studied prospectively 188 consecutive patients with suspected primary BC, negative at axillary clinical examination. Ten minutes after 740 MBq 99mTc-tetrofosmin injection, planar and SPECT scintimammography were acquired, followed by axillary P-SPECT imaging.
Results. At histology, 12 patients had benign mammary lesions and 176 had BC. Axillary lymph node dissection (ALND) was performed in all BC patients, bilaterally in 3 cases: 74/179 axillae had metastases. P-SPECT showed a significantly higher overall sensitivity than SPECT and planar (93.2% vs 85.1% and 36.5%, respectively; p<0.05 and p<0.0005, respectively) and was false negative in 5 patients with 1 metastatic node each, micrometastatic in 4/5 cases; SPECT and planar were also false negative in these 5 cases and in 6 and in 42 further cases, respectively. P-SPECT added important prognostic information by distinguishing single from multiple and ≤3 from >3 nodes; only P-SPECT defined the exact number of nodes in 15/25 patients with 2-4 nodes. P-SPECT showed the highest accuracy and NPV: 92.7% and 95%, respectively (SPECT 90.5% and 90%, respectively; planar 73.2% and 68.9%, respectively).
Conclusion. 99mTc-tetrofosmin axillary P-SPECT appears highly accurate in BC non palpable axillary lymph node metastasis detection and significantly more sensitive than both planar and SPECT, its few false negative results predominantly concerning micrometastases; moreover, only P-SPECT gave additional important prognostic information. Given its very high NPV, P-SPECT could also be used to better select patients who might avoid ALND.