Hormone therapy blocks or removes hormones
Metastatic breast cancer is the most advanced and lethal stage of breast cancer. Cancer cells have spread to other organs beyond the breast in patients with metastatic breast cancer.
The body uses hormones to tell the cells to grow and to divide. Hormone therapy aims to block hormones that stimulate growth and division of breast cancer cells. Estrogen is a hormone associated with growth of breast cancer tumors. For metastatic breast cancer, hormone therapy focuses on blocking estrogen. Thus, unlike other cancer treatments that focus on killing cancer cells, hormone therapy focuses on blocking growth of cancer cells.
If your tumor is estrogen-receptor positive (also known as ER-positive), it will grow rapidly in a high-estrogen environment. On the other hand, if your tumor is estrogen-receptor negative (ER-negative), it is not affected by the estrogen level in your body. Therefore, ER-negative breast cancers would not benefit from therapies that block estrogen, according to the American Cancer Society.
Blocking production of hormones by surgery or radiation treatment
The first hormone therapy ever used for treating metastatic breast cancer is oophorectomy, which is a surgical procedure that removes ovaries. The surgery is often done via a laparoscope and will leave scars. Alternatively, radiotherapy can be used to stop ovaries from working permanently. It would take three to five months following radiotherapy for the ovaries to completely stop producing hormones.
Blocking production of hormones by drugs
There is a wide range of commercially available agents that can be used to treat metastatic breast cancer, including progestins, tamoxifen, aromatase inhibitors and fulvestrant.
Patients are treated with one hormone first, which may become ineffective after a time. This is referred to as first-line treatment. Patients then receive second-line treatment based on another hormone.
Typically, the first-line treatment is associated with 30 to 50 weeks of tumor control, while the second-line treatment is associated with 15 to 25 weeks of tumor control.
The most well-known hormone therapeutic agent is tamoxifen, a selective estrogen-receptor modulator (SERM). It blocks estrogen from attaching to estrogen receptors on breast cancer cells. According to UpToDate.com, tamoxifen has a 50 percent response rate among ER positive tumors and has been shown to improve survival of metastatic breast cancer patients significantly. Klijn et al. (2001) showed that tamoxifen combined with surgery improved survival compared to treatment with either surgery or tamoxifen alone.
Tamoxifen has many side effects, including increasing risk of endometrial cancer, stroke and cataracts.
References
- American Cancer Society: Hormone Therapy
- Klijn JG, Blamey RW, Boccardo F, et al. Combined tamoxifen and luteinizing hormone-releasing hormone (LHRH) agonist versus LHRH agonist alone in premenopausal advanced breast cancer: a meta-analysis of four randomized trials. J Clin Oncol 2001;19(2):343
- Are hormone receptors present?
