Relation of FDG uptake of breast cancer and the histologic and the biologic characteristics of the tumor
Authors: Thabet Mirette Rafik Helmy , Kamel Faten Mohammed Mahmoud , Ali Wafaa Raafat 
Published: October 2021

Abstract

Background
Breast cancer is considered the most common type of cancer and the second leading cause of cancer-related death among women. The prognostic factors including histological type, tumor nuclear grade, tumor size, and preoperative tumor-nodes-metastasis (TNM), hormone receptor and immunohistochemical molecular markers in the specimens, define the prognosis and survival rate. Early diagnosis and accurate follow-up of these patients affect the management. 18F-fluoro-2-deoxy-d-glucose positron emission tomography (FDG PET) has proved to be an effective and accurate imaging technique for a variety of diagnostic oncology tasks in breast cancer, lymph node staging, staging and restaging of recurrent and metastatic disease, and treatment follow up. Sufficient knowledge of the initial characteristics of breast tumors that may affect 18F-FDG uptake is essential for optimal use and interpretation of 18FFDG PET/CT imaging. Several pioneering studies have investigated the correlation between the affinity to 18F-FDG uptake and some of the histological and biological characteristics such as tumor type, grade, hormonal receptor status and HER2 status.

Objective
To correlate the relation of 18F-fluoro-2-deoxy-D-gIucose (18F-FDG) positron emission tomography/ computed tomography (PET/CT) uptake in breast cancer to histopathological and biological characteristics.

Methods
A prospective descriptive study over the course of 6 months from August 2019 till February 2020. It included twenty five patients with pathologically proven breast carcinoma referred to the Radiology department, Ain Shams University Hospitals/ Private centers for a preoperative 18FDG PET/CT scan.

Results
For the tumors in 25 women, the mean SUVmax was 4.75±2.55. Primary tumor 18FFDG uptake ratio was correlated with patients' age (P = 0.032), tumor size (P = 0.034), histological grade (P=O.OI 8), estrogen and progesterone negativity (P = 0.012), Her2/neu positivity (P = 0.012), high Ki-67 level (&gt;10%) (P = 0.024), axillary lymph node involvement (P = 0.038) and distant metastasis (P = 0.039). High Ki-67 level (Pearson Correlation Coefficient= 0.457; 95% confidence interval; P = 0.037) and tumor size (Pearson Correlation Coefficient =0.458; 95% confidence interval, P = 0.021) were determining factors for high 18F-FDG uptake values. The histological type (P = 0.525) was not significantly correlated with 18F-FDG uptake.

Conclusion
FDG PET imaging was used to estimate tumor biologic behavior of breast cancer such as histopathologic grading, immunohistochemistry, axillary lymph node status and distant metastasis. SUVmax correlated with several of pathological prognostic factors may have potential for predicting the prognosis of breast cancer. 18F-FDG PET/CT could be a useful tool to pretherapeutically predict biological characteristics and baseline risk of breast cancer Increased 18FFDG uptake on PET/CT was correlated with a high Ki-67 proliferation index and larger tumor size. These results suggest a potential role of 18F-FDG PET/CT in identifying tumor aggressiveness.