Up to 80% of all cases of breast cancer are classified as ER-positive. In this type of breast cancer, the tumour forms as a reaction to the production of estrogen. Up to 65% of these types of cancer are also classified as PR-positive. In the case of a PR-positive breast cancer, the tumour grows in reaction to progesterone. Finally, if your breast tumour contains a large number of receptors for either of these hormones, then your cancer is classified as hormone-receptor positive.
ER2 Breast Cancer Treatment
Breast cancers that are diagnosed as ER or PR-positive are typically addressed through the use of hormone therapy as opposed to ER or PR-negative tumours. In some cases, patients begin hormone therapy following an operation, a course of chemotherapy, or radiation therapy. These supplementary therapies work by lowering the risk of a relapse by diminishing the effects of estrogen. The primary options include tamoxifen, aromatase inhibitors such as anastrozole, or CDK 4/6 inhibitors such as palbociclib.
HER2-Positive
In up to 20% of breast cancer cases, the cells produce an abundant amount of a protein referred to as HER2. A breast cancer that is HER2-positive typically grows quite fast and becomes extremely aggressive.
Women who have been diagnosed with HER2-positive breast cancer can use trastuzumab or Herceptin to significantly lower the risk of a recurrence. In most cases, this medication is used in conjunction with a course of chemotherapy following an operation in patients with metastatic breast cancer. This drug is also reserved for the treatment of cases of early-stage breast tumours. That said, the medication has been linked to an increased risk of cardiovascular and pulmonary problems. The research into the ideal duration of treatment with maximum efficacy is still ongoing.
There is another medication known as lapatinib that is preferred in cases where trastuzumab proves ineffective. Another option is ado-trastuzumab emtansine in combination with taxanes (a chemotherapy medication). For patients who are awaiting surgery, a combination of pertuzumab and other chemotherapy drugs may be necessary.
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