In particular, MRI of the breast can be used as a problem-solving tool in the evaluation of patients in whom equivocal abnormalities are identified by mammography or physical examination [44] and [45]. MRI is particularly appealing for surveillance of young women due to its proven higher sensitivity compared to mammography, especially in dense breasts [46], [47], [48], [49] and [50]. However, due to the relatively low specificity of MRI for BC recurrence (range from 66 to 100%) [51], [52], [53], [54], [55], [56], [57] and [58]

and the current high cost of this technique [59], MRI could not be considered a recommendable tool in BC follow-up. Moreover, a recent study showed that MRI did not reduce the risk of both local and distant disease relapse [60]. For these reasons mammography is the cornerstone of appropriate BC follow-up after primary treatment for all patients [12]. In the early 1990s it has been reported Birinapant that a small percentage of metastatic breast cancer (MBC) patients who achieved a complete remission after systemic treatment remained disease-free over 20 years. Overall, these long-survivors represented only 1–3% of all metastatic patients, but they challenged a paradigm: MBC was no longer always a fatal condition [61] and [62]. Looking into the patient and tumor characteristics of the long-survivors we realized that they shared some important

features: they were young, with good performance status and with a limited burden of metastatic disease [63] and [64]. In particular, having an oligometastatic disease seemed Fluorouracil chemical structure to be the strongest predictor for long survival. Over the last three decades, several studies confirmed this assumption. The implementation of multidisciplinary aggressive approach in patients with a single metastatic lesion has lead to a disease-free interval longer than 15 years [65], [66], [67], [68] and [69], and a retrospective analysis of patients with 1 or 2 metastatic sites showed a complete response with systemic treatment of 48% and a 20-year OS rate of 53% [62]. These impressive

results can be related with both an improvement in treatment Phospholipase D1 for MBC and an improvement in early detection of metastatic disease limited to 1–2 sites. However, more than 20% of patients have a multiple sites disease at presentation of metastatic spread [70]. According to a recent retrospective analysis, the most common sites of distant recurrence were bone (41.1%), lung (22.4%), liver (7.3%), and brain (7.3%) [62]. Interestingly, different patient and tumor characteristics underlined different patterns of distant relapse: bone metastases were more likely to be diagnosed in patients with HR-positive disease, lung and liver metastases in patients with a more advanced stage at the time of primary diagnosis, and brain metastases in patients with HR-negative disease [29] and [62].