The metastasis patterns and their prognostic features in patients with de novo metastatic breast cancer of different ages.

Purpose: The prognostic outcomes of metastasis patterns in patients with de novo metastatic breast cancer (dnMBC) of different ages are unknown. Our study used a large-scale data to investigate the metastasis patterns and prognostic features in dnMBC of different ages.

Methods: Total 24,698 women with dnMBC in the Surveillance, Epidemiology and End Results database (2010-2018) were divided into three groups by age. Chi-squared test was used to compare metastasis patterns and logistic regression was performed to investigate the risk of age and specific organ metastases. Kaplan-Meier survival curves were used to compare the overall survival.

Results: In three groups, young group had the largest proportion of liver metastases (35.2% vs. 28.2% vs. 21.1%, p < 0.001), and elderly group had the largest proportion of lung metastases (22.6% vs. 30.0% vs. 35.0%, p < 0.001) and the lowest proportion of bone metastases (65.7% vs. 67.6% vs. 64.4%, p < 0.001). In young group, patients with liver metastases had better prognosis than patients with lung metastases (MST: 34 months vs. 29 months, p = 0.041), but in middle-aged and elderly groups, the prognosis of lung metastases was better than that of liver metastases (MST in middle-aged group: 24 months vs. 20 months, p = 0.002; MST in elderly group: 12 months vs. 6 months, p < 0.001).

Conclusion: DnMBC patients at different age have distinct metastasis patterns and prognostic features. The findings lend support to consideration of tailored management and surveillance strategies for different age patients.