The surfaces of breast cancer cells have a variable number of sites called estrogen and progesterone receptors. Estrogen and progesterone are two naturally-occurring female hormones. Each tumor specimen is tested for these receptors. The number of such receptors on cancer cells determines the sensitivity of the cells to the influence of these hormones. If a significant number of cells in a particular tumor show estrogen and/or progesterone sensitivity, the tumor is said to be estrogen- and progesterone-receptor (ER/PR) positive. The implication is that such tumors are stimulated by these hormones and may respond to removal or blocking of these substances (hormonal therapy).
A peculiarity of breast cancer and a few other cancers is that it may recur late. Although most cancers that recur (including breast cancer) do so in the first five years, breast cancer also may recur 10 or even 20 years after the initial incident. For this reason, long-term surveillance is critical in this disease.
Advanced disease that has spread to the rest of the body is difficult to treat
Advanced disease that has spread to the rest of the body is difficult to treat and slow down using the methods currently available. Treatment which relieves symptoms but does not cure the disease is called palliative. Chemotherapy and hormonal therapy may slow the progress of the disease. Trials of high-dose chemotherapy now underway result in destruction of vital bone marrow and necessitate bone-marrow transplant or peripheral stem-cell transplantation.
There are some promising developments on the horizon in breast cancer treatment.