Past

It is known that locoregional therapy (LRT) in metastatic breast cancer contributes to local control and also prolongs systemic progression-free survival and overall survival.1 However, metastatic breast cancer reflects a heterogeneous group of diseases with a broad spectrum. Tumor load, metastatic site, and biological characteristics of the tumor determine the clinical course. Although having a metastatic disease is the most significant factor in shortening overall survival, bone-only metastasis is a special entity in terms of both its biological behavior and clinical course.2 Bone-only metastases are present in more than half of de novo metastatic patients.3 Retrospective trials concluded that LRT should be evaluated in bone-only metastatic patients in prospective studies and that the extent, type, and sequencing of LRT should be studied.

Present

Protocol BOMET MF14-01 is a multicenter prospective registry study. Patients with bone-only metastases at diagnosis were included. The study had three groups of patients: group 1 received only systemic therapy, group 2 systemic therapy prior to LRT, and group 3 received LRT after systemic therapy. In this study, LRT prolonged overall survival and systemic progression-free survival with reducing locoregional recurrence.4 The timing of LRT was not an independent contributing factor on survival. Although survival was longer in patients with solitary and oligometastasis, overall survival was longer in multiple metastatic patients who had LRT as well.

Future

Such a large prospective multicenter registry study focusing on a single metastatic site has not been presented before. For current practice, while planning treatment of patients with only bone metastases at the time of diagnosis, the primary LRT alternative can be discussed in tumor board and with patient. To adapt surgery in guidelines and clinical practice routinely, there is an unmet need for randomized studies to evaluate of LRT in patients with bone-only metastasis.