Breast Cancer: Hormone Therapy

Hormone therapy for breast cancer treatment

One of the most important test results doctors look at when treating a woman with breast cancer is whether her tumor cells contain receptors for the hormones estrogen and progesterone. If present, these hormones can fuel cancer cell growth, and hormone therapy -- which stops them -- can be a very effective weapon in the treatment arsenal.

The presence of receptors

ER positive means tumor cells have receptors for estrogen, and PR-positive means the tumor has progesterone receptors. About 75 percent of breast cancers are estrogen-receptor positive and of those, about 65 percent are also PR-positive. These hormones can fuel rapid cancer cell growth, so the goal is to "turn off" this action by blocking the receptors.

Despite the similar names, hormone therapy is not the same as Hormonal Replacement Therapy, or HRT, which many women take during and after menopause. In fact, HRT isn't considered safe for women with breast cancer.

Which hormone therapy drugs are best?

For years, tamoxifen (brand name Nolvadex, though it's now a generic) was the standard drug of choice for women with hormone-receptor-positive breast cancer. Tamoxifen is a type of drug known as a SERM, which stands for selective estrogen-receptor modulator.

There are newer SERMs being studied and introduced for breast cancer. Raloxifene (brand name Evista) was developed to treat osteoporosis but has been shown to work well for invasive breast cancer. Another SERM, Toremifene (brand name Fareston), is similar to tamoxifen but is rarely used in the U.S., though it's popular in Europe. But tamoxifen is by far the most widely used and prescribed.

New drugs for postmenopausal women

Aromatase inhibitors

Many cancer specialists now believe that a new group of drugs called aromatase inhibitors work better than tamoxifen in postmenopausal women. Several large clinical trial results have been published since 2007 showing that aromatase inhibitors are more effective at preventing recurrence and have fewer side effects.

The reason seems to be that in postmenopausal women, most estrogen is no longer produced by the ovaries but, rather, is converted from another hormone, androgen. Aromatase inhibitors work by preventing the enzyme aromatase from triggering the androgen into estrogen conversion. The names of the drugs are letrozole (brand name Femara), anastrozole (brand name Arimidex), and exemestane (brand name Aromasin).

An even more recent drug

Estrogen-receptor antagonists have recently come into use, and, like SERMs, they block estrogen. However, only one, fulvestrant (brand name Faslodex), has won FDA approval, and it's used solely when other types of hormone therapy have failed.

How hormone therapy is delivered

Tamoxifen, the most common hormone therapy, is taken as a pill every day for five years. This may seem like an eternity, but studies have shown that it can prevent or postpone recurrence if taken over a long period of time. Aromatase inhibitors are usually taken the same way, orally every day for five years.

Are there side effects or risks from hormone therapy?

By blocking or turning off estrogen, hormone therapy causes symptoms similar to menopause, though it doesn't cause actual menopause. These include hot flashes and night sweats, vaginal dryness and itchiness, headache, and fluid retention or weight gain.

Premenopausal women may also develop irregular periods. Tamoxifen causes more of these types of symptoms than do aromatase inhibitors. In addition, tamoxifen has been linked with an increased risk of stroke, blood clots, cataracts, and uterine cancer. Aromatase inhibitors have fewer side effects, but this type of hormone therapy can cause joint pain and decreased bone density.


Melanie Haiken

Melanie Haiken discovered how important it is to provide accurate, targeted, usable health information to people facing difficult decisions when she was health editor of Parenting magazine. See full bio

over 4 years, said...

I started out on Tamoxifen and was switched over to Anastrozole when it as determined I was officially in Menopause. I was having trouble on the Tamoxifen with pain, and I was hoping the new drug would help change things. I don't see any change in weight, and the pain seems worse, which would coincide with this article. My breast surgeon was discussing this with me, and she said new studies were showing that women kept on Tamoxifen for longer amounts of time had less recurrence of cancer. She did say here are always new studies!

over 4 years, said...

My oncologist is insisting on tamoxifen. I am post menopausal, my cancer found early. I had a lumpectomy in Aug 2013 and have just started the beginning of 33 radiation treatments. I will consider aromatase inhibitors, but I know nothing about them. Can anyone help me with this? I will refuse tamoxifen as I am post menopausal.

about 5 years, said...

What are the risks of re-introducing estrogen into my body, I was diagnosed with Breast Cancer 7 years ago, and now my doctor says I am in remission. There are no indicators (that the doctrs can see) that my breast cancer is in any way threatening, Now I find myself suffering terribly from not just "hot flashes" but being drenched all day long, my skin is deteriorating every day, and I am aging very, very quickly. I am just plain misereable, mood swings, anxiety, the inability to function properly on any level. I feel if I were to go back on Premarin it may help, but I am afraid to take any chances, but these side effects of being taken off of estrogen, cold turkey, after being on it for 29 years is life altering more than anything else. It has been 7 years since I had my mastectomy and I am nt getting better with the hot flashes, I am gettting worse, and it is debilitating. I have tried all kinds of herbal remedies. I am currently trying Yam Cream but it is not helping either. There comes a time when quality of life must be consideted, and I have NO QUALITY now, and I need help.

about 7 years, said...

ive been so moody since ive started chemo. my moods are all over the place, my family says im driving them nuts, im also diabetic, im having problems controling my diabetis. since ive started chemo.

about 7 years, said...

I would like to know the difference between Tamoxifien and Arimidex. I was first prescribed Tamoxifen 20mg, but due to putting on weight my specialist nurse has changed me to Armidex 1mg. can anyone tell me if by taking a smaller dose will impeid my chances of breast cancer not returning

almost 8 years, said...

I've been on Femara for the past 2 1/2 years; this has clarified its properties and (ESPECIALLY!!) its side effects. My oncologist has his own mother on Femara, so I feel pretty good about taking it!