Pretreatment PET in breast cancer: is there a role?

Abstract

Breast carcinoma shows greater heterogeneity than the vast majority of adenocarcinomas and carries a highly variable prognosis dependent on a wide range of factors, including tumour size and stage, histological subtype, grade, hormone receptor status and a growing range of molecular abnormalities. Accurate preoperative prognostication is highly important in selecting the most appropriate individualized therapy for a particular patient, and considerable interest is now being focused on noninvasive imaging as a means to achieve this. The ability of F-FDG PET/CT to combine functional and anatomical data has contributed enormously to oncology [1], and in particular to the emerging field of personalized medicine [2], but it has not yet found a routine role in the preoperative assessment of breast cancer. We ask here whether this situation is likely to change. F-FDG PET already plays an important part in the work-up and monitoring of metastatic or recurrent breast cancer [3], where it is especially valuable in restaging. Its ability to provide an early and accurate assessment of response to therapy has also made a substantial contribution to the management of patients with both locally advanced and metastatic disease [4]. It may also have a role in primary staging for distant disease in selected high-risk patients, such as those with large (over 3 cm in diameter) tumours, where in one prospective study it achieved excellent sensitivity and specificity in the detection of distant metastases (100 % and 98 %, respectively) and led to a change in the initial staging in 42 % of patients [5]. A further series suggested that preoperative PET/CT can have a significant impact on initial staging and on clinical management in patients with early-stage breast cancer with tumours larger than 2 cm [6]. In addition to detecting distant metastases in 15 % of these patients, PET showed unsuspected synchronous primary carcinomas at other sites in 2 % of patients. The findings of another study on early breast tumours were also promising [7]. PET/CT had the potential to impact management in approximately 16 % of patients. Whether PET has a place in routine preoperative assessment is still unclear, however, and the quality of the evidence for its use in this setting was regarded as only “moderate” in the most recent (2008) Society for Nuclear Medicine (SNM) guidelines [3]. An increasing body of data is, however, accumulating to support the suggestion that PET may provide valuable predictive prognostic information, and could usefully contribute to the preoperative decision-making process. The study by Vinh-Hung et al. in a recent issue of European Journal of Nuclear Medicine and Molecular Imaging examines this potential role for PET, and suggests that the identification by PET of positive axillary nodes is predictive of nodal involvement and represents a useful tool for treatment decision making which can reduce the need for sentinel lymph node biopsy (SLNB) [8]. The potential role of PET in preoperative staging in breast carcinoma has been considered in detail by two large systematic reviews which analysed a total of 10 studies of between 18 and 167 patients [9, 10]. These reviews were examined by a multidisciplinary expert panel under the auspices of the SNM to develop recommendations on the role of PET in oncology [3]. Their analysis showed that if axillary lymph node dissection (ALND) is used as the reference standard, PET demonstrates a sensitivity of 40– 93 % and a specificity of 87–100 % in the detection of axillary nodal metastases. If SLNB is used as the reference, PET achieves a sensitivity of 68–96 % and a specificity of 57–80 % [3]. PET accuracy is lower when evaluated against S. Chua The Royal Marsden NHS Foundation Trust, Sutton, UK