Table III.

Multivariate analysis of prognostic factors affecting progression-free survival of patients with BOM.

Variable	Hazard ratio	95% CI	P-value
HR status at breast cancer diagnosis
Negative	1.00	Reference	–
Positive	0.63	0.40-0.92	0.027
Number of bone metastases at BOM diagnosis
Multiple	1.00	Reference	–
Single	0.64	0.45-0.91	0.013

The factors with P<0.05 in the univariate analysis in Table II were incorporated in the multivariate analysis. Tumor stage, HER2 status and molecular subtype at primary diagnosis were adjusted for. HR, hormone receptor; BOM, bone-only metastasis.