Axillary staging with 18F-FDG PET/CT in early breast cancer: impact of tumor subtypes.

BACKGROUND

Breast cancer is one of the most common cancers in women globally. Axillary lymph node metastasis remains one of the most independent prognostic factors in breast cancer.

OBJECTIVE

Evaluate the diagnostic accuracy of 18F-FDG-PET/CT in detecting axillary lymph node metastasis based on immunohistochemical subtypes and its correlation with sentinel lymph node biopsy (SLNB) results.

DESIGN

A retrospective cohort.

SETTING

Tertiary oncology center in Turkiye.

PATIENTS AND METHODS

Patients diagnosed with early-stage invasive ductal breast cancer and who underwent preoperative F-18 fluorodeoxyglucose positron emission computed tomography (18F-FDG PET/CT) evaluation were included in the study. Patients were divided into five immunohistochemical subtypes: Luminal A, Luminal B HER2 (-) (human epidermal growth factor receptor 2), Luminal B HER2 (+), HER2 (+), and triple negative. SLNB and SUVmax (Maximum Standard Unit Value) results were compared.

MAIN OUTCOME MEASURES

Diagnostic accuracy of 18F-FDG PET/CT for detecting axillary metastasis was the primary outcome. Interrater reliability testing in determining the agreement between 18F-FDG PET/CT and SLNB was the secondary outcome.

SAMPLE SIZE

RESULTS

The sensitivity, specificity, PPV, NPV and accuracy of 18F-FDG-PET/CT for detecting axillary metastasis were 62%, 92%, 88%, 71% and 77%, respectively. Cohen's Kappa coefficient (0.54) showed moderate agreement with SLNB (<.001). Tumors with positive HER2 gene amplification [HER2 (+) and Luminal B HER2 (+) have higher sensitivity than other subtypes (Luminal A, Luminal B HER2 (-) and triple negative). HER2 gene amplification also increases the agreement between 18F-FDG-PET/CT and SLNB results.

CONCLUSION

18F-FDG-PET/CT has a high specificity but low sensitivity for ipsilateral axillary metastasis in invasive ductal carcinoma. The presence of HER2 gene amplification can increase sensitivity and concordance with SLNB.

LIMITATIONS

Retrospective design and limited number of patients for each subtype.