Correlation with the histopathologic factors and metabolic change in dual time point F-18 FDG PET/CT imaging in breast cancer

Objectives This study was to evaluate the utility of the dual time point imaging of FDG PET/CT in detecting primary breast cancer and to determine whether the histopathologic factors have an effect on FDG uptake and its change over time.

Methods Thirty-seven patients with newly diagnosed breast cancer underwent 2 sequential PET/CT scans for preoperative staging. Patients were divided into 2 or 3 groups according to the histopathologic factors such as invasiveness(invasive vs non-invasive), tumor size(≤10 mm vs >10mm) and grade. The peak SUV(pSUV) of tumor and contralateral normal breast was measured from both time points. The percentage of change in pSUV(Δ%pSUV) and tumor-to-background ratios of pSUV(Δ%T/B ratio) between time point 1(pSUV1) and 2(pSUV2) was calculated.

Results Of the 37 cancer lesions, 24(64.9%) showed an increase and 13(35.1%) showed decrease in the pSUV over time. After correcting with the pSUV of contralateral normal breast, 35(94.6%) of the 37 cancer lesions demonstrated an increase in the pSUV. The mean±SD of pSUV1, pSUV2, Δ%pSUV and Δ%T/B ratio were 7.7±5.5, 8.4±6.6, 4.7±16.9% and 33.4±22.4%. Firstly, in the comparison between two groups by size, pSUV1 and pSUV2 were significantly different(p<0.05). Δ%pSUV and Δ%T/B ratio were not significant(p=0.927, 0.379). Secondly, in the comparison between two groups by invasiveness, pSUV1, pSUV2 and Δ%pSUV were significantly different(p<0.05). However, Δ%T/B ratio were not significant(p=0.079). Thirdly, in the comparison between two groups by grade, all results were not significant(p>0.05).

Conclusions Dual time point imaging is a simple and noninvasive method that may improve the accuracy of FDG PET/CT in assessing patients with breast cancer. The pSUV is significantly different at each time point among subgroups by the histopathologic factors. The histopathologic factors may not significantly influence the Δ%pSUV and the Δ%T/B ratio in breast cancer