The relationship of 18F-FDG PET/CT SUVmax values with molecular subtypes and hormone receptors in breast cancer patients

Positron Emission Tomography–Computed Tomography (PET-CT) serves as a complementary imaging modality in breast cancer staging and therapeutic monitoring. SUV (standardized uptake value) represents the concentration of 18F-fluorodeoxyglucose (18F-FDG) radiotracer per tissue volume, normalized for injected dose and body weight. This study explored associations between 18F-FDG PET/CT (derived SUVmax measurements and breast cancer molecular classifications, assessing metabolic variations across subtypes characterized by hormone receptor expression patterns. We enrolled breast cancer patients who underwent 18F-FDG PET/CT scanning at the Surgical Oncology Department, Health Sciences University Faculty of Medicine, Gulhane Training and Research Hospital. We investigated relationships between maximum standardized uptake values (indicating metabolic activity) and molecular classifications. Additionally, we examined correlations between SUVmax and immunohistochemical markers such as Ki-67 proliferation index, HER2 (human epidermal growth factor receptor 2), ER (Estrogen receptor) and PR (progesterone receptor) expression. Our analysis encompassed 102 patients. Molecular subtype categorization demonstrated statistically significant SUVmax differences (p<0.001). Triple-negative malignancies showed notably elevated SUVmax compared with Luminal A (p<0.001), Luminal B HER2(-) (p<0.001), Luminal B HER2(+) (p<0.001), and HER2-enriched (p<0.001) categories. Similarly, isolated HER2(+) cases displayed higher SUVmax than Luminal A (p<0.001), Luminal B HER2(-) (p<0.001), and Luminal B HER2(+) (p<0.001) subtypes. Negative correlations emerged between SUVmax and ER/PR expression, whereas positive relationships were found with Ki-67 index. From a clinical perspective, SUVmax functions as a biomarker representing tumor biological characteristics rather than simply a quantitative measurement. Our results suggest that 18F-FDG PET/CT warrants expanded integration in comprehensive breast cancer care. The demonstrated elevated metabolic activity in aggressive subtypes highlights this modality's utility as an adjunctive prognostic tool.