Radiation therapy for primary tumor of de novo stage IV breast cancer

Despite recent advances in multimodality treatments such as endocrine therapy, chemotherapy, molecularly targeted therapy, and radiation therapy, it is still very difficult to cure de novo stage IV breast cancer patients completely. The traditional role of radiation therapy for these patients has been a palliative treatment strategy that aims to control tumor progression and suppress tumor related symptoms. Recently, several non-randomized retrospective studies on de novo stage IV breast cancer have revealed that locoregional radiation therapy (LRRT) might confer a survival benefit. However, there is no high level evidence to support the impact of LRRT on survival among patients with de novo metastatic disease so far. This article aimed to summarize the literature and to discuss whether treating the primary lesion with radiation therapy could improve clinical survival outcomes among de novo stage IV breast cancer patients. The issue of patient selection will be discussed because not all de novo stage IV breast cancer patients could benefit from LRRT. This article also explores the clinical evidence regarding LRRT for de novo metastatic disease across various cancers such as prostate, uterine cervical, non-small-cell lung, and head and neck cancers. Many retrospective trials have shown the impact of locoregional treatment (LRT) on survival in de novo metastatic breast cancer. However, since the backgrounds of patients treated with LRRT are quite different from those of patients who did not receive LRRT and the treatment consists of surgery and/or radiation therapy, the role of radiation therapy alone remains unclear. Several reports investigated prognostic factors to detect the benefits of LRRT, which still remains conflicting and no consensus exists. However, selected patients with de novo metastatic disease with better performance status, low tumor burden, and estrogen receptor positivity should be considered for the addition of radiation therapy delivered to the primary site. To explore proper decision-making regarding LRRT, further prospective randomized trials are eagerly awaited.