Yes.
Onions are a very healthy food. Not only do they help lower blood fats, but they may also have anti-cancer properties. One study found that the sulfides contained in onions have some cytotoxic effects, interfering with the growth process of breast cancer cells and may prevent breast cancer from spreading and metastasizing.
This effect has not been confirmed in humans. But given the other benefits of onions, breast cancer patients may want to eat more of them.