Value of 18F-FDG PET/CT for primary tumor visualization and staging in T1 breast cancer patients

Background: The use of 18F-FDG PET/CT in large and locally advanced breast cancer has been investigated extensively, but uncertainty remains regarding its value in early stage breast cancer. The aim of the present study was to assess the accuracy and yield of FDG PET/ CT for primary tumor visualization and staging in T1 breast cancer patients. Methods: Sixty-two patients with invasive T1 breast cancer, who received baseline PET/CT within the scope of two clinical trials, were evaluated. Image acquisition of the thorax was done in prone position (hanging breast technique), followed by whole body scanning in supine position. Primary tumor FDG uptake was qualitatively and quantitatively evaluated and compared with clinical and histopathological characteristics. Presence of locoregional and distant metastases and other events was assessed and compared with conventional imaging procedures. Results: The primary tumor was visible with PET/CT in 54 (87%) of 62 patients, increasing from 59% in tumors ≥10 mm to 98% in tumors over 10 mm. All triple negative and HER2-positive tumors and 40/48 (88%) of ER-positive/HER2-negative tumors were visualized. FDG uptake was significantly higher in triple negative, grade 3, and highly proliferative tumors. Sensitivity and specificity of PET/CT in the detection of axillary metastases were 73% and 100%, respectively. In two (3%) patients PET/CT depicted FDG-avid periclavicular nodes, which were detected with ultrasound as well. Of 12 distant lesions, one was confirmed to be a lung metastasis, three were false positive, and eight were new primary proliferative lesions. No metastases were missed. Conclusion: Using optimal imaging of the thorax and breasts, the majority of small invasive breast carcinomas (cT1) can be visualized with FDG PET/CT. Specificity in the detection of axillary metastases is excellent, allowing immediate axillary lymph node dissection in case of an FDG-avid axillary node. However, sensitivity was limited, requiring a sentinel lymph node biopsy in case of absence of FDG-avid nodes. Distant staging can be done relatively reliably, but the yield in T1 tumors is low.