I thought when they do a mastectomy there are no more breasts for the cancer . However as in a friend of mines case when they do the surgery they say it’s 98 percent effective . They will never say 100 percent. This is because there is the chance that one little cancer cell can escape and start growing again somewhere . My friend’s has spread and she has been that way for several years . She refused chemo and radiation post mastectomy. She was very healthy too when she got it . Was negative for genes .She does however live a very full life. it’s about 9 years now.