|What Is Tamoxifen?
Tamoxifen (brand name Nolvadex) is the oldest and most popular drug used in the treatment of breast cancer (it was FDA approved over 30 years ago). Like chemotherapy, tamoxifen is a systemic therapy, which means that it treats the whole body, not just one area. It may be prescribed to:
1. Prevent cancer returning to the same area after a tumor has been removed (known as adjuvant therapy).
2. Reduce the likelihood of cancer appearing in the other breast.
3. Stop or slow the growth of cancer which may have spread to other parts of the body (metastatic breast cancer).
4. Reduce the size of a breast lump before surgery (neoadjuvant therapy).
5. Decrease the chance of the disease developing in women with high risk factors for breast cancer. This includes women with a strong family history of the disease who tested positive for BRCA gene mutations (see breast cancer genetic testing for more details).
Tamoxifen is sometimes prescribed in cervical cancer recurrence cases. Clinical trials show encouraging success rates.
How Does It Work?
Tamoxifen is a hormone medication taken as part of a hormone therapy program. Specifically it belongs to a class of drugs called selective estrogen receptor modulators (SERMs). Estrogen can promote the growth of breast cancer in some women. SERMs work by blocking the effects of estrogen in those with estrogen-sensitive types of breast cancer. About 70 percent of women with breast cancer are estrogen receptor-positive (ER-positive) which means they are a candidate for tamoxifen. Initially researchers thought tamoxifen worked by starving cancer cells of estrogen so that they stopped growing. Now it appears that the mechanism is more complex. It may be that the drug fools the cancer cell into accepting the imposter (the SERM) as a real hormone, or it may act in some other way that we have yet to discover.
What Is The Dosage?
The usual dosage is one 20-40 mg tablet a day. Daily doses of 40mg are usually split in half, the first part taken in the morning and the second part in the evening. If you miss a dose, take it as soon as you remember. However if is near the time the next dose is due, skip the missed pill and continue with your regular schedule. Never take a double dose to catch up.
Women who are also taking anticoagulants (blood thinners) like warfarin should be closely monitored. As should those taking hormone methods of birth control such as patches, implants and pills; as well as those taking St John's wort, rifampin or phenobarbital. Some medications can reduce the effectiveness of tamoxifen; these include SSRI antidepressants like paroxetine and fluoxetine.
There may be some risk to a fetus if taken by pregnant women but the benefit of the drug may in some cases out-weigh the risk. Women should not breastfeed while taking tamoxifen.
What Are The Side Effects?
Although hormone therapy drugs like tamoxifen are different to hormone replacement therapy (HRT) used for the treatment of menopause symptoms, they can produce similar side effects. Note: SERMs acts to reduce the effects of estrogen in the body, while HRT seeks to increase its effects.
Common Side Effects
• Hot flashes and night sweats.
• Vaginal dryness.
• Hair thinning.
• Leg cramps.
• Irregular periods in premenopausal women.
If any of the above symptoms persist or worsen, tell your doctor. In some cases you may experience increased cancer pain and/or increased tumor size when starting tamoxifen. This is usually a good sign because it means the drug is working. The symptoms should disappear again quickly.
Less Common Side Effects
• Risk of blood clots, particularly in the legs and lungs.
• Stroke. Seek immediate attention if you have signs of stroke.
• Cataracts (clouding of the eyes so vision is reduced).
• Eye pain.
• Persistent vomiting or nausea.
• Signs of infection (sore throat, fever).
• Yellowing skin and eyes.
• Swelling (edema) of the hands or feet.
• Endometrial cancer.
• Bone loss (osteoporosis) in premenopausal women.
• Depression, mood swings and loss of libido.
• Uterine polyps and cervical polyps. In fact some doctors now insist that all users should have an annual Pap smear test and pelvic examination to check for polyps.
How Long Will I Need To Take It?
After Treatment For Breast Cancer
Until recently the guidelines recommended women to take tamoxifen everyday for 5 years after their cancer had gone into remission. However with the advent of newer hormone therapies, some of which appear to be as good as tamoxifen in trials, additional approaches are becoming popular. Some women are given an aromatase inhibitor for 5 years instead of tamoxifen, while others may be given an aromatase inhibitor for 2 or 3 years after taking tamoxifen for 5 years.
Furthermore, one large-scale study by Oxford University (2012) found significant benefits in continuing taking tamoxifen for 10 years after remission. The results of the study showed that cancer returned in 25 percent of women given 5 years of tamoxifen compared with 21.4 percent in those given the drug for 10 years. Deaths from breast cancer were also significantly reduced from 15 percent in the 5 year group to 12 percent in the 10 year group.
Bottom line: The decision about which drug and how long to take it after your cancer has gone into remission needs to be taken on an individual basis in consultation with your oncologist (doctor who specializes in the treatment of cancer).
To Prevent Breast Cancer
Women considered high risk of breast cancer, but who have not developed the disease are also recommended to take tamoxifen for 5 years. The Breast Cancer Prevention Trial (BCPT) reported that women who took tamoxifen over 5 years were 42 percent less likely to develop breast cancer than those who took a placebo. Read also about Evista, another medication which helps to prevent invasive breast cancer in women after menopause.
How Much Does It Cost?
The cost of a monthly supply of generic tamoxifen is about $100.