Association between ¹⁸F-FDG uptake and molecular subtype of breast cancer

To determine whether (18)F-FDG uptake in breast cancer correlates with immunohistochemically defined subtype and is able to predict molecular subtypes.

This retrospective study involved 306 patients with 308 mass-type invasive breast cancers (mean size 2.65 cm, range 1.0-15.0 cm) who underwent (18)F-FDG PET/CT before therapy. The correlations between primary tumour (18)F-FDG uptake on PET/CT, expressed as SUVmax, and clinicopathological findings and molecular subtype, i.e. luminal A, luminal B (HER2-negative), luminal B (HER2-positive), HER2-positive and triple-negative, were analysed. The predictors of these subtypes were investigated.

The mean SUVmax of the 308 tumours was 5.33 ± 3.63 (range 1.15-19.01). Among the subtypes of the 308 tumours, 87 (28.2 %) were luminal A, 111 (36.0 %) were luminal B (HER2-negative), 31 (10.1 %) were luminal B (HER2-positive), 26 (8.4 %) were HER2-positive and 53 (17.2 %) were triple-negative, and the corresponding mean SUVmax were 3.41 ± 2.07 (range 1.18-14.30), 5.17 ± 3.52 (range 1.35-19.01), 6.57 ± 3.84 (range 1.42-15.58), 7.55 ± 3.63 (range 2.30-13.60) and 6.97 ± 4.17 (range 1.15-16.06), respectively. A cut-off value of 3.60 yielded 70.1 % sensitivity and 66.1 % specificity with an area under the receiver operating characteristics curve (AUC) of 0.734 for predicting that a tumour was of the luminal A subtype. A cut-off value of 6.75 yielded 65.4 % sensitivity and 75.2 % specificity with an AUC of 0.704 for predicting a HER2-positive subtype.

SUVmax, a metabolic semiquantitative parameter, shows a significant correlation with the molecular subtype of breast cancer, and is useful for predicting the luminal A or HER2-positive subtype.