Curcumin also slows the rate at which rogue cells reproduce, said researchers at the University of Louisville, Kentucky.
Previous research has found that curcumin has anti-cancer properties but most of it gets broken down once it is in the stomach.
So researchers packed circumin inside miniature dissolving capsules - each one just two millimetres long and containing 200 milligrammes of powder.
Tumour-ridden mice were implanted with two capsules each over four months while another group was fed a diet of curcumin, the 'Daily Express' reported.
The results showed that "the implants resulted in significant reduction in both the tumour multiplicity and tumour volume while the dietary curcumin was ineffective."
Curcumin works by blocking the effects of hormones that feed the growth of breast cancer cells, researchers believe.
Further research will now look at whether directly injecting the spice ingredient into tumours could help women beat breast cancer.
The study has been published in the journal Cancer Prevention Research.