Recurrent breast cancer develops from cells that originally came from the primary breast tumor. The cancer returns after the initial treatment and a period of time when no cancer was detected. This can happen because treatment did not fully destroy or remove all the cancer cells. Even with surgery, microscopic clusters of cancer cells may have been left behind that were too small to be detected with any available test.

If the cancer is aggressive, isolated cells may survive the rounds of chemotherapy, hormone therapy and radiation meant to prevent a recurrence.

Sometimes cancer cells may be dormant for years without causing harm. Then something happens that activates the cells, so they grow and make other cells. Not all of the growth factors for cancer have been found.

It's also possible to develop a new tumor, called a second or new primary tumor, in the same breast as the first tumor or in the other (contralateral) breast. This is not considered recurrent breast cancer. Women who've had breast cancer have a higher risk of developing cancer in the other breast than do women who've never had breast cancer. The risk of developing a new tumor in the second breast is higher if you have a strong genetic predisposition or hereditary breast cancer. Fortunately, most women who have cancer in one breast never develop cancer in the opposite breast.

Many women who have a cancer recurrence blame themselves. But, even when you do everything right, cancer can sometimes come back.

May. 24, 2011