Preoperative FDG PET/CT in breast cancer patients: where are we going?

Abstract

Breast cancer remains the commonest female malignancy in Western countries and the second leading cause of cancer mortality in women [1]. Accurate staging at the time of the initial diagnosis plays a major role in the choice of therapeutic modalities for an optimal management of these patients [2]. Breast cancer staging includes assessment of cancer spread to regional lymph nodes and also to distant sites. Being a whole-body procedure, PET/CT is able to assess all these data in a single test, providing morphological information and also evaluating the metabolic activity of the disease. However, FDG PET/CT is not currently indicated for primary breast cancer diagnosis, mainly due to its poor spatial resolution. Indeed, diagnostic accuracy depends on primary breast tumour size as reported by Cermik et al. In this series the sensitivity of FDG PET to detect nonpalpable, small (<10 mm) invasive malignancies ranged from 53 to 63 % for T1mic/T1a and T1b tumours, respectively [3]. In addition, PET imaging accuracy is affected by tumour histology: invasive lobular carcinomas are detected with less sensitivity than ductal carcinomas [4, 5]. Conversely, the detection of high intensity, focal FDG uptake in the breast has a strong positive value for cancer [6]. In practice the main contribution of PET in local tumour assessment consists in measuring FDG uptake by the standardized uptake value (SUV), which is useful to evaluate early response to neoadjuvant therapy in those cases not submitted to surgery directly. Indeed, while morphological changes due to therapy activity are not detectable until 4– 6months of treatment, metabolic changes occur earlier and are assessable even after one or two cycles of systemic therapy [7, 8]. This allows the oncologist to anticipate surgery, if needed. According to several studies FDG PET/CT could provide some important clinical and biological information about the disease aggressiveness [9–11], even if the degree of FDG uptake in the primary tumour has not proven to be an independent predictor of outcome [12, 13]. In addition to tumour size, the status of the axillary lymph nodes is the most reliable prognostic indicator for recurrence and survival in early breast cancer. None of the current imaging procedures has sufficient sensitivity to substitute the sentinel node biopsy (SNB) in the histopathological evaluation of the axilla. In particular, PET/CT showed poor sensitivity for axillary staging, with values as low as 20 % in some series [14, 15]. This is especially true for breast cancer patients with very restricted disease spread to the axilla, because of the limited spatial resolution of the technique and the presence of few FDGavid cells in case of micrometastases. Vinh-Hung et al. reconfirmed these data with their paper published in the present issue of the European Journal of Nuclear Medicine and Molecular Imaging. The authors retrospectively evaluated 104 patients, who underwent preoperative FDG PET/CT for breast cancer staging and surgery as part of planned primary therapy. The diagnostic utility of the preoperative PET scan in the assessment of axillary lymph node involvement was reported: among 63 PET node-negative patients, 26 were histopathological node-positive and among 41 PET node-positive patients, 36 were histopathological node-positive. These data confirm This editorial commentary refers to the article http://dx.doi.org/10.1007/ s002259-012-2181-1.