Similar Prognosis of Patients with Bone-only Metastatic Breast Cancer and Visceral Metastasis

Background: Bone-only metastatic breast cancer is believed to be non-life-threatening, and mild therapy is frequently selected to avoid adverse events of drug therapy. However, the prognoses of such patients are not well studied. Methods: Patients who received drug therapies for metastatic breast cancer between 2004 and 2016 at our institution were divided into the “Bone-only metastasis”, “non-visceral”, and “visceral” groups based on the mode of the first metastasis, and the efficacy of the first-line therapy and survival of these patients were compared. Results: There were 131 eligible patients, and the bone-only metastasis, non-visceral, and visceral groups included 26, 25, and 80 patients, respectively. The median survival time (MST) of the overall survival (OS) in each group was 35.1, 34.9, and 37.4 months, respectively (p=0.71). The clinical benefit rates of first-line therapy in the bone-only metastasis, non-visceral, and visceral groups were 66.7%, 45%, and 69.3%, respectively, and the MST of the time to treatment failure (TTF) in each group was 6.3, 5.5, and 5.8 months, respectively, showing that the efficacy of first-line therapy did not significantly differ among the groups. In the bone-only metastasis group, patients with <5 metastases tended to have a good prognosis, and those with a low nuclear grade and long first-line therapy duration had a significantly better prognosis than others. Conclusion: The patients with bone-only metastasis had a similar prognosis and treatment response to those with other modes of metastasis, and the patients with a good response to the first-line therapy had a good prognosis.