Something to remember

For most women with stage I or II breast cancer, breast-conserving surgery (BCS) plus radiation therapy is as effective as mastectomy. Survival rates of women treated with these 2 approaches are the same.

In deciding which type of surgery to have for early-stage breast cancer, the choice is not between saving your breast and saving your life. Women with early-stage breast cancer who have breast-sparing surgery live just as long as those who have mastectomy. A woman’s life expectancy is the same no matter which surgical choice she makes.
When women are told that the survival rates of both approaches are the same, they might be surprised or skeptical. Some women assume that breast cancer won't return if the whole breast is removed. However, some breast tissue is left behind even after mastectomy, and cancer can recur in that tissue or on the nearby chest wall. For women with early-stage breast cancer who choose breast-sparing surgery, research clearly shows that radiation therapy after surgery lowers the risk of recurrence. The risk of cancer returning in the same breast is low. Yet, even if breast cancer does recur in the same breast, that does not reduce a woman's chances for a healthy recovery. As was already noted, the chance of survival is not affected by the choice of surgery. However, a recurrence in the same breast could require more surgery, and a woman may decide to have a mastectomy at that time.
The type of surgery does not affect the risk of cancer in the healthy breast or elsewhere in the body.

womenshealth.gov