Role of radiotherapy in oligometastatic breast cancer: Review of the literature

Metastatic breast cancer has been historically considered as an incurable disease. Radiotherapy (RT) has been traditionally used for only palliation of the symptoms caused by metastatic lesions. However, in recent years the concept of oligometastatic disease has been introduced in Cancer Medicine as a clinical scenario with a limited number of metastases (≤ 5) and involved organs (≤ 2) with controlled primary tumor. The main hypothesis in oligometastatic disease is that locoregional treatment of primary tumor site and metastasis-directed therapies with surgery and/or RT may improve outcomes. Recent studies have shown that not all metastatic breast cancer patients have the same prognosis, and selected patients with good prognostic features as those younger than 55 years, hormone receptor-positive, limited bone or liver metastases, a low-grade tumor, good performance status, long disease-free interval (> 12 mo), and good response to systemic therapy may provide maximum benefit from definitive treatment procedures to all disease sites. While retrospective and prospective studies on locoregional treatment in oligometastatic breast cancer demonstrated conflicting results, there is an increasing trend in favor of locoregional treatment. Currently, available data also demonstrated the improvements in survival with metastasis-directed therapy in oligometastatic breast cancer. The current review will discuss the concept of oligometastases and provide up-to-date information about the role of RT in oligometastatic breast cancer.