Hormone Therapy

Hormone Therapy

Hormone therapy works by blocking estrogen that causes cell-proliferation. It is used for adjuvant therapy and for advanced cancers in patients with hormone receptor-positive tumors. Over the past few years, many new anti-estrogen drugs have become available. Generally they do one or more of the following:

• Block the hormone receptor itself
• Suppress estrogen production
• Destroy the ovaries (which produce estrogen)

Tamoxifen and Selective Estrogen Receptor Modulators (SERMs)

Tamoxifen (Nolvadex) has been the standard hormonal drug used for breast cancer. It is the prototype for a growing class of compounds called selective estrogen receptor modulators (SERMs). SERMs chemically resemble estrogen and trick the breast cancer cells into accepting it in place of estrogen. Unlike estrogen, however, they do not stimulate breast cancer cell growth. Other SERMs being studied for breast cancer include toremifene (which is very similar to tamoxifen), idoxifene, and droloxifene.

Candidates. Tamoxifen is used for any cancer stage in women of all ages who have hormone receptor-positive cancers. In addition, it is being used to protect against cancer in high-risk women.

Tamoxifen as Adjuvant Therapy. When used as adjuvant therapy for early stage hormone receptor positive breast cancer, tamoxifen is well-tolerated for 5 years. Evidence shows that taking it for 5 years significantly improves survival rates and reduces recurrence. Taking it longer appears to confer no additional advantages. Patients whose tumors are convincingly hormone receptor-negative do not benefit. Comparisons between tamoxifen and other SERMs used for adjuvant therapy are underway.

Side Effects. Hormone therapy with SERMs has fewer side effects than chemotherapy, but can still cause hot flashes, vaginal bleeding and discharge, and visual disturbances.

Of concern is an increased risk for blood clots, which can, in rare cases, be life-threatening. Tamoxifen, and possibly toremifene, pose a long-term increased risk for uterine (endometrial), cancer, though not enough to offset the benefits from breast cancer prevention. Any woman on tamoxifen with vaginal bleeding should see her doctor immediately to rule out uterine cancer. Early evidence indicates that some of the newer SERMs may not increase the risk for uterine cancer. Long-term studies are needed.