Purpose: This study investigates the correlation of retention index (RI) using the dual phase FDG PET/CT scan with the breast cancer biomarkers.
Methods: A total of 55 patients with breast cancer underwent dual phase FDG PET/CT scans (60 and 120 min after FDG injection) before treatment. SUVmax and SUVmean of the primary breast tumors were measured, then the percent change of SUVmax and SUVmean between the two scans were calculated, and denoted as RImax and RImean, respectively. After the surgical resection of the breast tumor, the status of biomarkers (ER, PR, and HER-2) was evaluated in the postsurgical specimen.
Results: RImean was significantly higher in ER (-) (median, 16.2; IQR, 10.8-21.0) or HER-2 (+) (median, 16.1; IQR, 10.7-21.6) tumors than in ER (+) tumors (median, 9.9; IQR, 5.5-15.3) or HER-2 (-) tumors (median, 10.5; IQR, 5.5-16.1). However, there were no significant differences of SUVmax or RImax according to the ER or HER-2 status. There were no significant differences of any PET parameters between PR (+) and PR (-) tumors. Based off ROC curve analyses, RImean predicted the ER (+) tumors (AUC, 0.699; p = 0.006), and HER-2 (+) tumors (AUC, 0.674; p = 0.022), but not the PR (+) tumors. However, neither SUVmax nor RImax predicted ER (+), PR (+), or HER-2 (+) tumors.
Conclusions: Retention index of SUVmean can reflect the ER and HER-2 status of breast cancers. Higher retention index of SUVmean might associate with lower ER expression and higher HER-2 expression.
Keywords: Breast cancer; Dual phase; Estrogen receptor; Human epidermal growth factor receptor 2; Positron emission tomography; Retention index.