The purpose of this study was to evaluate the prognostic significance of computed tomography (CT)-attenuation of tumor-adjacent breast adipose tissue for predicting recurrence-free survival (RFS) in patients with breast cancer. They retrospectively enrolled 287 breast cancer patients who underwent pretreatment 18F-fluorodeoxyglucose (FDG) positron emission tomography PET/CT. From non-contrast-enhanced CT images of PET/CT; CT-attenuation values of tumor-adjacent breast adipose tissue (TAT HU) and contralateral breast adipose tissue (CAT HU) are measure.
PET/CT CT-attenuation values
Difference (HU difference) and percent difference (HU difference %) in CT-attenuation values between TAT HU and CAT HU are calculate. The relationships of these breast adipose tissue parameters with tumor factors and RFS are assess. TAT HU was significantly higher than CAT HU (p < 0.001). TAT HU; HU difference, and HU difference % showed significant correlations with T stage and estrogen receptor and progesterone receptor status (p < 0.05), whereas CAT HU had no significant relationships with tumor factors (p > 0.05).
Patients with high TAT HU; HU difference, and HU difference % had significantly worse RFS than those with low values (p < 0.001). In multivariate analysis, TAT HU and HU difference % were significantly associated with RFS after adjusting for clinico-pathologic factors (p < 0.05). CT-attenuation of tumor-adjacent breast adipose tissue was significantly associated with RFS in patients with breast cancer. The findings seem to; support the close contact between breast cancer cells and tumor-adjacent adipocytes observed with imaging studies.
Energy to tumor cells
Adipose tissue is one of the major components of the human body; found all around the body. In non-lactating human breast tissue, up to 56% of the total breast volume consists of adipose tissue. Although adipose tissue is mainly compose of adipocytes, it is also comprised of various other kinds of cell types including immune cells, endothelial cells; pre-adipocytes, and fibroblasts. For a long time, adipose tissue was considered to function as a simple storage organ of excessive energy; however, evidence showed that adipose tissue also function as an endocrine organ secreting hundreds of cell signaling proteins, called adipokines.
Previous studies published over the last decade have continuously demonstrated that adipose tissue could play a role in cancer growth, progression, and metastasis by secreting multiple kinds of adipokines, inducing inflammatory micro-environment, remodeling the extracellular matrix, and providing energy to tumor cells. Furthermore; adipocytes in the close vicinity of cancer cells can have crosstalk with cancer cells, which increases the potential of tumor progression and metastasis.
Breast adipose tissue
Because of the close localization between mammary epithelium and breast adipose tissue, breast cancer is consider as one of the most representative malignancies that is in close contact with adipose tissue, along with gastric, colon, and ovary cancers. In previous cell-culture and histopathological studies of breast cancer, it has already prove that breast cancer cells have active interaction with peritumoral adipose tissue, which further enhances aggressiveness and invasiveness of breast cancer cell.