The purpose of this study was to investigate the association between the tumor uptake of these 2 tracers in invasive ductal carcinoma and to examine the correlation of uptake of each tracer with prognostic factors and tumor molecular subtypes

Fluorine-18 fluorodeoxyglucose (FDG) positron-emission tomography/computed tomography (PET/CT) is a well-known molecular imaging technique used to evaluate oncologic diseases.

The maximum standardized uptake value (SUVmax) of FDG as a semiquantitative index has been shown to correlate with prognostic factors in breast cancer and to be useful for assessing the response to chemotherapy. Recent studies have reported that SUVmax differs among the molecular subtypes of breast cancer.

Breast-specific gamma imaging (BSGI) using technetium-99m (99mTc) sesta-methoxyisobutylisonitrile (sestamibi) is reported to have a high diagnostic performance as an excellent adjunct modality to mammography for detecting breast cancer. 

Sestamibi uptake by tumor is affected by angiogenesis, regional blood perfusion, and mitochondrial membrane potentials, while FDG uptake reflects glucose utilization. Thus, the 2 tracers reflect different functional properties of tumor. However, similar to SUVmax of FDG on PET/CT, the tumor-to-background ratio (TBR) of sestamibi on BSGI has also been shown to predict the prognosis of breast cancer.

Results

A total of 96 patients with invasive ductal carcinoma who underwent preoperative breast-specific gamma imaging and FDG positron-emission tomography/computed tomography were retrospectively enrolled. Tumor-to-background ratio (TBR) of sestamibi and maximum standardized uptake value (SUVmax) of FDG were correlated with each other. Each of them was then compared with prognostic factors and molecular subtypes.

In all tumors, there was a moderate positive correlation between TBR and SUVmax (r = 0.520, P < .001). Both TBR and SUVmax were significantly correlated with tumor size, an incidence of axillary lymph node metastasis, histologic grade, estrogen receptor, progesterone receptor status, and Ki-67.

There is a moderate degree of association between TBR of sestamibi and SUVmax of FDG in the invasive breast cancer. Two imaging indexes showed a similar tendency related to prognostic factors and molecular subtypes. While both TBR and SUVmax were significantly different between luminal A and nonluminal A tumors, neither of them had high enough sensitivity or specificity to obviate pathologic and molecular diagnosis.