The Role for PET Scanning in Breast Cancer Staging
Abstract & Commentary
By William B. Ershler, MD, Editor
Synopsis: The role for PET scanning is not yet established for the staging of newly-diagnosed breast cancer or for patients in whom recurrent disease is suspected. The current report from a single European institution compared positron emission tomography using 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG-PET) with conventional imaging (radiographs, bone scintigraphy, ultrasound) and with computed tomography (CT). FDG-PET was more sensitive than conventional studies and comparable to CT. Although FDG-PET and CT provided similar diagnostic accuracy, the information was often found to be complementary.
Source: Mahner S, et al. Comparison between positron emission tomography using 2-[fluorine-18]fluoro-2-deoxy-D-glucose, conventional imaging and computed tomography for staging of breast cancer. Ann Oncol. 2008;19:1249-1254.
Defining the optimal imaging approach for staging of breast cancer is a goal for both patient welfare and economic considerations. Prior to the introduction of positron emission tomography using 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG-PET), conventional strategies employed physical examination, chest radiography, abdominal ultrasound and bone scintigraphy, with the addition of bone radiographs when necessary. Computerized tomography (CT) and magnetic resonance imaging (MRI) have been used at some centers with increasing frequency.
The intent of staging is to identify the extent and localization of distant metastases in an effort to develop the most effective cancer treatment strategy. In a retrospective review of a series of breast cancer patients treated at the University of Hamburg-Eppendorf, Mahner and colleagues compared the diagnostic performance FDG-PET with that of CT and conventional imaging including chest radiography, abdominal ultrasound and bone scintigraphy.
A total of 119 consecutive patients with newly diagnosed locally advanced disease (n = 69) or previous history of breast cancer (n = 50) who had clinical suspicion of metastatic disease underwent FDG-PET, CT and conventional imaging procedures. Imaging results were retrospectively compared with histopathology and clinical follow-up which served as reference standard for the presence or absence of metastatic disease.
FDG-PET detected distant metastases with a sensitivity of 87% and a specificity of 83%. In contrast, the sensitivity and specificity of combined conventional imaging procedures were 43% and 98%, respectively. CT was performed on only 61 of the subjects and was contrast-enhanced in only 40. Nonetheless, CT revealed a sensitivity of 83% and a specificity of 85%.
The authors concluded that for breast cancer staging, FDG-PET is superior to conventional imaging procedures for detection of distant metastases. Although FDG-PET and CT provided similar diagnostic accuracy, the information was often found to be complementary.
Commentary
Although FDG-PET has been extensively studied in a variety of clinical settings, its role in the evaluation of breast cancer remains inconclusive. The current report comparing FDG-PET to conventional imaging approaches is of value because of the relatively large series of patients included and the inclusion of data regarding sensitivity and specificity at various anatomical locations (eg, lung, liver, bone, nodes, and chest wall). In the liver, for example, FDG-PET proved more sensitive for detecting metastatic lesions than ultrasound, but less sensitive than CT. This in contrast to published experience in the detection of colorectal metastases in the liver in which FDG-PET seems to be somewhat more sensitive than CT.1, 2 In lymph nodes, particularly those in the mediastinum, FDG-PET has the potential to pick up metabolically-active small, but cancer-involved nodes below the detection level of CT.3, 4 Thus, although overall sensitivity and specificity are comparable, FDG-PET and CT offer complementary information, strengthening the rationale for combining the two techniques.
In general, the findings of FDG-PET used alone (ie, without CT) are consistent with those from other studies. A meta-analysis of 18 published reports of FDG-PET for the evaluation of breast cancer recurrence or metastases found a sensitivity of 92.7% and a specificity of 81.6%5 similar to the 87% sensitivity, 83% specificity reported in this study. Of course, with increasing availability of FDG-PET/CT, it should now become a priority to conduct prospective studies to determine if this imaging technique alone would be sufficient to accurately stage breast cancer.
References
1. Ogunbiyi OA, et al. Detection of recurrent and metastatic colorectal cancer: comparison of positron emission tomography and computed tomography. Ann Surg Oncol. 1997;4(8):613-620.
2. Schiepers C, et al. Contribution of PET in the diagnosis of recurrent colorectal cancer: comparison with conventional imaging. Eur J Surg Oncol. 1995;21(5):517-522.
3. Bellon JR, et al. Evaluation of the internal mammary lymph nodes by FDG-PET in locally advanced breast cancer (LABC). Am J Clin Oncol. 2004;27(4):407-410.
4. Eubank WB, et al. Detection of locoregional and distant recurrences in breast cancer patients by using FDG PET. Radiographics. 2002;22(1):5-17.
5. Isasi CR, et al. A meta-analysis of FDG-PET for the evaluation of breast cancer recurrence and metastases. Breast Cancer Res Treat. 2005;90(2):105-112.
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