Wormwood contains artemisinin, which is an herbal supplement used in Traditional Chinese Medicine. It is currently being studied as a treatment for cancer. It is usually used to treat malaria.
One article (1) looked at wormwood and its treatment of breast cancer cells. It noted that wormwood, when mixed with breast cancer cells was only able to kill 28 percent of them. However, when wormwood was mixed with iron, it kills 98 percent of the cells. Normal cells were not adversely affected in this study.
While the study showed that wormwood and iron could kill cancer cells in vitro, more research studies are necessary to see if breast cancer in humans can be helped with this combination of substances.
Source: 1.Little Known Chinese Herb & Iron Kill 98% Of Cancer Cells In 16 Hours. http://naturalsociety.com/artemesinin-iron-causes-98-reduction-breast-cancer/. Accessed 9/7/16.