I'd remove the word sternum and re-think that question....
Can a person die of cancer? YES.
Are you referring to breast cancer that has metastasized to the sternum? If so. it would help if you could provide us with more information about your case (type of BC, stage, treament to date, etc.).
Or to a primary cancer of the sternum? In that case, it would be preferrable for you to post in the Cancer Forum.
Best wishes...