99mTc-sestamibi scintigraphy in axillary lymph node metastases detection in patients with primary breast cancer undergoing curative surgery

Background: Lymph node status is the primary prognostic discriminant in patients with breast cancer (BC). Although axillary dissection represents the methods of choice for obtaining such information, less invasive staging procedures has been suggested. Preoperative non-surgical techniques include ultrasonography, CT-scan, MRI, 18F-FDG PET, and positive radiopharmaceutical scintigraphy. The aim of this study was to evaluate the usefulness of 99mTc-sestamibi scintigraphy (SS) in patients with confirmed primary BC undergoing surgery. Patients and Methods: A series on 159 women (median age 54 years, range 36-78 years) with confirmed primary BC were enrolled in the study. Breast-conserving surgery or mastectomy with axillary dissection was performed in all patients, as indicated by the tumor staging. Once they had given the informed consent, each patients underwent SS. Images were acquired using a single detector gamma-camera equipped with a parallel hole low-energy high-resolution collimator (256 x 256 matrix, 140 keV energy setting) 10 minutes after 750 MBq radiopharmaceutical I.V. administration, using single-photon emission computed tomography (SPECT) technique. A focal 99mTc-sestamibi uptake and a mass-to-background ratio of more than 1.4 was considered as a positive result in detection of axillary node metastases. Results: Final pathology showed 33 (20.8%) pT1b, 90 (56.6%) pT1c, and 36 (22.6%) pT2 breast carcinomas. The greatest diameter of the tumor (size) ranged from 6 and 30 mm (median n16 mm). Sixty (37.7%) patients had axillary metastases at surgery (N1), while 99 (60.3%) patients had negative nodes (NO). The average of nodes removed was 19.9f2.1, and the average of positive nodes was 2.7A1.2. The age of the patients significantly correlated with both size (R=0.24, F=9.55, p=0.002) and the number of positive nodes (R=0.33, F=7.11, p=0.0005), and subsequently there was a direct relationship between number of positive nodes and size (R=0.31, F=6.08, p=O.O16). Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of SS were 61.4%, 91 .O%, 84.2%, 91 .O%, and 87.4%, respectively. The sensitivity was higher in patients with 3 or more positive nodes (N=27/28, 96.40/o), while patients with 2 (N=25) and 1 (N=7) positive nodes the sensitivity was 80.0% and 28.6%, respectively. Conclusions: 99mTc-sestamibi scintigraphy may be useful in patients undergoing surgery for breast cancer, although its sensitivity is low when the number of involved nodes is two or less. This suggests that others imaging techniques should be used in conjunction with SS when a preoperative assessment of axillary lymph node status is required.