1. Overall survival ‐ subgroup analyses.

Overall survival subgroup analysis	Number of studies	N	HR	Lower CI	Upper CI	P value
HER2‐positive	2	192	0.90	0.60	1.35	NS
HER2‐negative	2	421	0.85	0.67	1.08	NS
ER positive	2	426	0.79	0.61	1.03	NS
ER negative	2	200	1.01	0.73	1.40	NS
Bone‐only metastasis	2	226	0.91	0.49	1.69	NS

CI: confidence interval
 ER: oestrogen receptor
 HR: hazard ratio
 NS: not significant