The Effects of Cancer Chemoprevention

For years, clinicians have actively sought to prevent and reduce cancer. Chemoprevention is the latest of such cancer-prevention efforts. Natural and pharmacological agents are being used as preventative cancer medicines, reversing malignant-cell progression by stimulating cells to repair damaged cells responsible for creating cancer (carcinogenesis). This new prevention strategy shows promise, but side effects and risks linked to these drugs may outweigh the benefits for some people. Only people considered high risk for developing cancer should consider using chemoprevention drugs.

SERMS

• Tamoxifen and raloxifene are selective estrogen receptor modulators (SERMS) that work to block the effects of estrogen. Approved for use by the FDA, both of these drugs are the best-documented chemoprevention drugs to date. Tamoxifen and raloxifene may not be 100 percent effective in preventing breast cancer, but they are both effective in reducing breast-cancer risk. Specifically, raloxifene has been quite effective in reducing invasive breast cancer, by about 50 percent. Tamoxifen has significantly reduced ER-positive breast cancer and sped up initial diagnosis for ER-negative breast cancer by one year.

What Classifies You as High Risk

• Doctors look at certain factors to determine whether patients are at high risk for developing cancer. In general, people predisposed to precancerous conditions are considered to be high risk. If cancer is prevalent within a family history, family members are at higher risk of developing cancer. In regards to breast cancer, women with a family history of breast cancer are considered to be at high risk and are candidates for tamoxifen or raloxifene. Women who have undergone hysterectomies are also deemed to be at higher risk for developing cancer, and are potential tamoxifen or raloxifene candidates as well.

Tamoxifen

• In blocking the effects of estrogen, tamoxifen helps prevent breast-tumor growths that can actually be influenced by estrogen (a reproductive hormone). Patients take tamoxifen orally on a daily basis for five years. Women 35 and older, menopausal or not, are candidates for tamoxifen if their Gail model risk score is 1.66 percent or higher. The Gail model helps predict a patient's likelihood of developing breast cancer by looking at age, family history and reproductive history. Patients prescribed tamoxifen may suffer from side effects such as bladder or urinary problems, hot flashes, nausea, irregular menstruation, or vaginal dryness or discharge.

Raloxifene (Evista)

• Similarly to tamoxifen, raloxifene blocks estrogen effects from the breast and surrounding tissues. However, unlike tamoxifen, raloxifene does not create estrogen-like effects on the uterus. Postmenopausal patients with Gail model scores above 1.66 percent are raloxifene candidates. Women suffering from osteoporosis may also be prescribed raloxifene. Side effects are similar to tamoxifen as well, and include bladder or urinary problems, hot flashes, joint and muscle pain, vaginal dryness or discharge, and possible weight gain.

Risks

• Tamoxifen and raloxifene are both associated with blood clots, endometrial and uterine cancer, as well as strokes. Tamoxifen may also cause cataracts. While both drugs increase blood-clot risks, raloxifene may actually cause fewer endometrial and uterine cancer cases as compared to tamoxifen. Similarly, raloxifene may cause fewer strokes in women with average heart-disease risks versus tamoxifen; however, patients with multiple heart-disease risk factors (high cholesterol and high blood pressure) may actually increase their chance of stroke by taking raloxifene.