Oligometastatic breast cancer: Are we there yet?

Patients with metastatic breast cancer are usually considered incurable. Recent advances have resulted in significant improvements in survival for patients with metastatic breast cancer. Due to the lack of randomised trials and heterogeneous disease biology, treatment decisions for patients with oligometastatic breast cancer vary widely. Some patients are treated similar to those with widespread disease while others are treated more aggressively. We conducted a review of the evidence for treatment options in oligometastatic breast cancer and consulted ClinicalTrials.gov to explore currently accruing or studies in development aimed at investigating oligometastatic disease in breast cancer. Surgery to the primary tumour in patients with metastatic breast cancer has failed to show any advantage over systemic therapy. However, there may be a benefit in women with controlled systemic disease who are hormone receptor positive with bone-predominant metastasis. Stereotactic radiotherapy has gained increased interest in this setting due to its excellent efficacy and lower rates of associated toxicity. A significant challenge remains in identifying the patient population who would benefit from such an approach, and to do so, we need to understand the distinct biology of oligometastatic breast cancer. Unique miRNA expression and low levels of tumour infiltrating lymphocytes in the immune micro-environment have been described in tumour tissues in patients with oligometastatic breast cancer. There is ongoing research aimed to better characterise these tumours, thus, allowing the selection of patients who would truly benefit from multi-modality treatment in an attempt for long-term survival and cure.