Role of 18F-FDG PET/CT in evaluating molecular subtypes and clinicopathological features of primary breast cancer.

OBJECTIVE: In this study, primary tumors' fluorine-18-fluorodeoxyglucose (F-FDG) uptake in luminal A, luminal B, triple-negative, and human epidermal growth factor receptor type-2 subtypes of breast cancer was evaluated. In addition, the relationship between the primary tumor maximum standardized uptake value (SUVmax) value and the presence of distant metastasis and axillary involvement was evaluated.

PATIENTS AND METHODS: Whole-body F-FDG PET/computed tomography (CT) imaging of 493 patients (mean age; 54.6±13.2 years) diagnosed with primary breast cancer were analyzed retrospectively. PET/CT imaging was obtained 60 min after the intravenous administration of F-FDG. F-FDG uptake of the lesions was assessed by calculating the SUVmax. Histopathological analyses were carried out on the basis of biopsy samples before PET/CT. For histopathological staging, the Scarff Bloom Richardson classification system was utilized, and patients were classified into luminal A, luminal B, triple-negative, and human epidermal growth factor receptor type-2 molecular subtypes.

RESULTS: 82.9% of the patients had invasive ductal carcinoma, 5.8% had invasive lobular carcinoma, 4.2% had apocrine carcinoma, 3.8% had mucinous carcinoma, and 3.4% has mixed carcinoma. Although the highest mean SUVmax was calculated in apocrine tumors (12.4±7.2), the lowest mean SUVmax was calculated in lobular carcinoma (6.8±4.6), and a statistically significant difference was found between the histological groups (P<0.001). F-FDG uptake was reported to be significantly higher in the triple-negative subtype than the luminal types, and in the luminal B subtype than the luminal A subtype. A statistically significant relation was found between primary tumor SUVmax and distant nodal, organ metastasis (P=0.003 and <0.001, respectively).

CONCLUSION: Increased primary tumor F-FDG uptake was associated with aggressive molecular subtypes in this study. The relationship of distant nodal and organ metastasis with primary tumor SUVmax showed that increased F-FDG uptake is important in terms of management of therapy and prognosis.