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Date
2021-09-17
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Abstract
Worldwide, breast cancer is the commonest female cancer and the leading cause of female cancer mortality in most countries, with over 2 million new diagnoses and 630,000 deaths in 2018 [1]. Thanks to mammographic screening programmes in most developed countries, many cancers are small at diagnosis. There is a clear relationship between the size of the primary tumour (T stage) and the presence of distant metastases (DM) at presentation. In patients with T1 tumours (smaller than 2cm), the incidence of DM is under 2%. Similarly, if fewer than 4 axillary lymph nodes are involved at imaging, the incidence of DM is under 4%, whereas in patients presenting with T3/4 tumours and N2 nodal disease (four or more abnormal nodes) the incidence of DM rises to 10-20% [2].
Thus, in patients with early stage disease (clinical stage 1-11A), all international guidelines state that screening for asymptomatic DM is not indicated (unless the patient has suspicious symptoms) [3,4]. It frequently generates false positive or indeterminate findings, with significant costs in terms of patient anxiety, resources and radiological follow-up. Though the presence of T3 disease (tumour > 5cm) is often regarded as an indication for whole-body staging, the incidence of DM in clinical stage 11B disease (T3N0, T2N1) is still low with conventional imaging. Units with this policy should robustly audit impact on patient outcomes.
For patients with clinical stage 111 disease, a whole-body technique is indicated for staging. Since the commonest sites of DM are the bones, lungs and liver, contrast-enhanced CT (CECT) is the most commonly used modality, being readily available and having acceptable diagnostic accuracy at these sites. Numerous studies have demonstrated that if the scan volume includes the neck and proximal femora, the additional yield from an isotope bone scan is extremely low [5].
The recent 8th edition of the AJCC TNM manual permits inclusion of tumour immunophenotype, which can be used to modify anatomical TNM staging. Aggressive HER2 amplified and ‘triple negative’ cancers (those without HER2 overamplification, oestrogen or progesterone receptor expression) demonstrate different patterns of metastatic disease, but there is as yet no convincing evidence for altering the strategy for staging according to tumour biology [6]. Again, though many oncologists request systemic staging prior to commencement of neoadjuvant chemotherapy for T1/2 tumours, there is little evidence for the utility of this approach.
More sophisticated cross-sectional techniques including PET-CT and whole body MRI (WB-MRI) are infrequently used for systemic staging in early stage breast cancer. However, there is good evidence that with increasing clinical stage, the incremental diagnostic yield from FDG PET-CT becomes significant [6], particularly for inflammatory breast cancer, where up to 30% of patients may be upstaged [6]. It is also very helpful in the evaluation of equivocal findings at CECT and in the identification of small volume nodal disease. WB-MRI is advantageous in the diagnosis of bone metastases and hepatic metastases, especially in low grade breast cancers such as invasive lobular cancer. With the continued evolution of personalised medicine and targeted therapies, it is likely that the approach to systemic staging will also evolve.
Citation
Vinnicombe, S. (2021). A13 Systemic staging for breast cancer: When and how? Cancer Imaging, 21(Suppl 1), Article A13. https://doi.org/10.1186/s40644-021-00422-6