When a breast biopsy shows that cancer is present, other tests are
used to find out which treatment will work the best.
Estrogen and progesterone receptor (ER/PR) tests identify whether
hormones affect the way the cancer grows. The hormones estrogen and
progesterone stimulate the growth of normal breast cells and some
breast cancers. Breast cancer cells that lack these
receptors (ER-negative and PR-negative cancers) are much less likely to respond
to treatment with such medicines as tamoxifen or aromatase inhibitors.
ER/PR-positive tumors have these receptors and are more likely to respond to
treatment with tamoxifen or aromatase inhibitors.
Note: Some citations in the text of this section are followed by a level of evidence. The PDQ editorial boards use a formal ranking system to help the reader judge the strength of evidence linked to the reported results of a therapeutic strategy. (Refer to the PDQ summary on Levels of Evidence for more information.)
Stage I, II, IIIA, and operable IIIC breast cancer often requires a multimodality approach to treatment. Irrespective of the...