A Cochrane review included 43 studies with a total of 9 742 women, 55% of whom were receiving first-line treatment for metastatic disease. For overall survival there was a statistically significant difference in favour of the combination regimens with no heterogeneity (HR 0.88, 95% CI 0.83 to 0.93; 36 studies, n=7147). Results were very similar when trials of first-line treatment were analysed, and for analyses where the single agent was also included in the combination regimen. Combination regimens showed a statistically significant advantage for survival over single agent taxane (HR 0.82, 95% CI 0.75 to 0.89; 8 studies, n= 2646), but not anthracycline (HR 0.94, 95% CI 0.86 to 1.02; 16 studies, n= 2985). Combination regimens were associated with significantly better time to progression (HR 0.78, 95% CI 0.74 to 0.82; 27 studies, n=6501) and response (RR 1.29, 95% CI 1.14 to 1.45; 46 studies, n=9 044) although significant heterogeneity was observed probably due to clinical diversity of the participants and interventions. Women receiving combination regimens experienced a statistically significant detrimental effect on white cell count, increased alopecia and nausea and vomiting.