Up to two-thirds of invasive breast cancers are classified as hormone receptor positive (ER+/PR+). Hormone receptor positive breast cancer has both estrogen receptor positive (ER+) and progesterone receptor positive (PR+) tumor receptor status. In other words, the relevant genes cause the cancer cells to express both estrogen and progesterone receptors. Compounds that regulate ER or PR expression, oppose the production of estrogen in the body (i.e., oppose aromatase) or inhibit estrogen binding to estrogen receptors are among those used to treat this type of breast cancer.
ER+/PR+ subtype has the most favorable prognosis
Breast cancer patients with ER+/PR+ tumors have the most favorable prognosis compared to the other estrogen/progesterone subtypes (ER+/PR-, ER-/PR+, ER-/PR-). Tumors with a large number of estrogen receptors are associated with a better the prognosis than those with few. Please see our article on ER+/PR+ breast cancer prognosis.
Some breast cancer risk factors are associated mainly with ER+/PR+
Late age at first period, early age at first birth, and increasing number of children have all been found to be associated with reduced risk of breast cancer, but only among those with ER+/PR+ tumors. Women with a history of migraine headaches are also less likely to develop ER+/PR+ breast cancer. Use of hormone replacement therapy (HRT) increases the risk of both ER+/PR+ and ER+/PR- tumors (but not ER- tumors). Women with high breast density have an increased risk for ER+/PR+ and mixed hormone receptor tumors but the association is less clear for ER-/PR- tumors. On the other hand, consumption of alcohol increases breast cancer risk for all ER/PR subtypes, as does a family history of breast cancer.
Patients with ER+/PR+ breast cancer have greatest opportunity to influence prognosis
There is some evidence that those with ER+/PR+ breast cancer have the greatest opportunity to improve their prognosis through diet, exercise, and by avoiding exposure to environmental estrogens. This advantage arises from the fact that this is the most hormonally driven subtype. Please see our article on what ER+/PR+ breast cancer patients and survivors should eat.