Implications of Standardized Uptake Value Measurements of the Primary Lesions in Proven Cases of Breast Carcinoma with Different Degree of Disease Burden at Diagnosis: Does 2-Deoxy-2-[F-18]fluoro-d-glucose-Positron Emission Tomography Predict Tumor Biology?

Objectives Tumor glycolytic activity as determined by 2-deoxy-2-[F-18]fluoro-d-glucose-positron emission tomography (FDG-PET) imaging is an important marker of tumor biology and provides critical information about the behavior of most malignancies at different stages of the disease. This study was undertaken to determine whether the degree of FDG uptake differs between the primary breast lesions with varying disease burden at diagnosis in proven cases of breast carcinoma. Materials and Methods Among 250 patients enrolled for this prospective study, 174 patients with newly diagnosed breast carcinoma at different disease stages who had undergone dual time point FDG-PET before any therapeutic or surgical interventions were considered for inclusion in this analysis. These patients prospectively underwent multimodality imaging techniques, such as magnetic resonance imaging (MRI), ultrasonography, digital mammography, computed tomography (CT), and dual time point FDG-PET, as a component of a National Institutes of Health-funded project for characterizing primary breast lesions and local–regional staging. The slice with maximum FDG uptake in the region of interest (ROI) was chosen for the first time point and the second time point images for quantitative measurement of the metabolic activity of the tracer (SUVmax1 and SUVmax2, respectively). Furthermore, the percent change in SUVmax (%ΔSUVmax) between SUVmax1 and SUVmax2 was calculated. Results The patient population (n = 174) were divided into three groups for the purposes of this study. Sixty-four patients with primary and metastatic axillary lymphadenopathy (designated as group I) and 18 patients with both axillary and distant metastases (designated as group II) met the inclusion criteria for this analysis. The third group (group III) comprised of a population of 92 patients without any metastasis either at the lymph nodes or at distant sites. The mean SUVmax1, SUVmax2, and the %ΔSUVmax in the early and delayed FDG-PET in group I (n = 64) patients were as follows: primary lesion 4.8 ± 3.9, 5.3 ± 4.5, and 9.4 ± 12.8%, respectively, and axillary lesions 3 ± 2.6, 3 ± 2.7, and 1.1 ± 21.3%, respectively. Among the group II patients (n = 18), the mean values of the primary lesion with regard to the SUVmax1, SUVmax2, and the %ΔSUVmax were 7.7 ± 6.2, 8.9 ± 7.1, and 15.7 ± 10.8%, respectively. The corresponding figures for the axillary lesions were 3.5 ± 3.1, 3.7 ± 3.1, and 6.3 ± 20.9%, respectively, and those for the distant metastatic lesions were 3 ± 1.4, 3.1 ± 1.2, and 8.5 ± 21.2%, respectively. The mean SUVmax1, SUVmax2, and the %ΔSUVmax of the primary lesion of group III patients (n = 92) without any metastasis were 2.9 ± 2.7, 3.4 ± 2.4, and 4.5 ± 4.2%, respectively. Unifactorial ANOVA of the three parameters among the primary lesions of these three groups were statistically significant with regard to the mean SUVmax1 (p = 0.01) and SUVmax2 (p = 0.01). These values in the primary lesions were highest in group II (those with both axillary and distant metastases), followed by group I (those with only metastatic axillary adenopathy) and group III (patients without any metastasis), and could be related to the more aggressive tumor biology in group II. Conclusion The findings provide evidence that among the lesions with varying disease burden at diagnosis, the FDG uptake is highest in cases with both axillary and distant metastasis, followed by those with axillary metastasis and then by those with no metastatic disease. These provide in vivo insight into tumor biology as FDG uptake is regarded as a surrogate marker of the same.