Relationship of 99mTc-uptake with prognostic factors of breast cancer, and causes of false negative results of scintimammography. Multivariate analysis using a logistic regression model

99mTc-sestamibi scintimammography (SSM) is a reliable diagnostic tool in breast cancer (BC) detection, and its complementary role in surgical planning is well established. The aims of this study were (1) to analyze the causes of false negative (FN) results of 99mTc-sestamibi scintimammography (SSM), and (2) to establish whether relationship exists between sestamibi uptake, evaluated as a tumor-to-background ratio (TB), and the main prognostic factors of BC. Patients and Methods: A group of 102 women (median age 58.17 years, range 32-86) with confirmed BC were reviewed. There were 33 (32.4%) premenopausal and 69 (67.6%) menopausal patients. All patients underwent SSM with the measurement of TB prior to surgery. The preoperative serum tumor markers CEA and CA 15-3 were above the cut-off in 16 (15.7%) and 27 (26.5%) patients. A TB of > 1.4 was considered a true positive (TP) result in detecting BC. Results: The overall sensitivity of SSM was 80.4%. No BC sized <7 mm were correctly detected by SSM. The final TNM staging was as follows: pT1aN0-1=6 (5.9%), pT1bN0=13 (12.7%), pT1bN1=5 (4.9%), pT1cN0=37 (36.3%), pT1cN1=5 (4.9%), pT2N0=19 (18.6%), pT2N1=17 (16.7%). There was no correlation between TB and (1) the age of the patients (r=0.086, p=0.39), (2) menopausal status (p=0.55), and (3) the axillary node involvement (p=0.47). We found positive correlation between TB and (1) the greatest diameter (size) of the tumor (r=0.32, p=0.0009), (2) the Ki-67 antigen expression (r=0.23, p=0.023), (3) the CEA (r=0.30, p=0.002) and CA 15-3 (r=0.22, p=0.026) serum levels, and the Bloom-Richardson grading (G1 vs. G2, and G2 vs. G3) (p<0.01). There was an inverse correlation between TB and both estrogen (r=-0.25, p=0.011) and progesterone receptor (r=-0.23, p=0.02) rate. The post-hoc analysis showed that size, CEA, and CA 15-3 were significantly (p<0.01) different between patients with FN SSM and those with true positive results, while the age did not differ (p=0.87). The logistic regression showed that only size and CA 15-3 represented true independent parameters, but the function was able to predict only 11 out of 20 (55.0%) patients with FN SSM. Conclusions: TB is independent of age and mainly correlates with the size of the tumor. There are no any reliable preoperative prognostic factors really useful for improving SSM sensitivity in patients with small BC.