The relationship between histopathological features, FDG uptake levels on PET-CT, and survival in breast cancer patients

Introduction and Aim: Breast cancer is the most common malignant tumor among women worldwide. It has been suggested that pre-treatment 18F-FDG PET/CT scans in pathologically diagnosed breast cancer can provide sufficient information about tumor biology, prognosis, and survival. The aim of our study is to investigate the relationship between FDG uptake parameters in 18F-FDG PET/CT performed at the time of diagnosis and the histopathological characteristics of the primary tumor in patients with a pathological diagnosis of breast cancer. Additionally, we aim to evaluate the relationship between tumor histopathological features, PET/CT FDG uptake parameters, and survival outcomes. Materials and Methods: The study retrospectively analyzed the demographic, clinical, histopathological and radiological data of 250 patients diagnosed with breast cancer and treated or followed up in the Medical Oncology Clinic of our hospital between July 2019 and July 2024 (a 5-year period). Data were obtained from the hospital database and patient files. The relationship between pre treatment 18F-FDG PET/CT uptake parameters and the histopathological characteristics of the primary tumor was examined, as well as the association of these parameters with survival outcomes. Triple-negative and HER2-positive patients were separately grouped, and survival analyses were conducted for each group. Results: Patients who passed away had statistically significantly higher rates of extra-axillary lymph node involvement, bone and liver metastases, axillary involvement, lymphovascular invasion, Stage 4 disease, progesterone receptor negativity, and ki-67 negativity compared to surviving patients (lymphovascular invasion p=0.002, ki-67 p=0.048, other comparisons p<0.001). Among all patients, 14% had triple-negative breast cancer, and 23.2% had HER2-positive disease. The PET/CT maximum standardized uptake values (SUVmax) for the breast tumor, metastases, and axilla were statistically significantly higher in 83 deceased patients compared to survivors (p=0.046, p=0.041, p=0.049). The mean expected survival time was 105.4 months. The overall survival rates were 83.3% at 5 years and 66.8% at 10 years. The 5-year survival rate was 74.3% in the triple-negative group and 88.5% in the HER2-positive group. Multivariate regression analysis identified lymphovascular invasion, stage, cerb-B2 positivity, tumor size/ breast SUVmax ratio as significant risk factors for mortality. Additionally, a tumor size/breast SUVmax ratio >0.95 was found to be a 2.3-fold significant risk factor for mortality compared to a ratio ≤0.95 (p=0.012). Conclusion: Prognostic factors should be determined for each patient, and treatment plans should be evaluated accordingly. Although Ki-67 and cerb-B2 positivity are known as poor prognostic factors, our study found that cerb-B2 positivity was associated with a reduced risk of mortality, likely due to the advancements in cerb-B2 targeted therapies in recent years. Keywords: Breast cancer; Histopathological features; FDG/PET-CT; SUVmax, Survival