The growing trend in treating hormone positive breast cancer is to stay on some kind of hormone blocker for a significant period of time.  Many women have told me that they fear stopping their tamoxifen or aromatase inhibitor because they think that it is only keeping cells under control, and that without the drugs the cancer will come back.

I always explain that studies have shown that tamoxifen’s benefits lasted well beyond the five years women were on it.  It seems like a period of hormone suppression has a long lasting effect, possibly by making any cells that are left dormant inactive or by changing the microenvironment (neighborhood) around the cells so that it keeps the cells in check.  Now we’ve got even more data to back that up.

Last month, the Early Breast Cancer Trialists Collaborative Group (EBCTG) reported in the Lancet an updated meta-analysis (a study that combines data from a number of studies) on the long-term benefit of five years of adjuvant tamoxifen.

The meta-analysis included a total of 21,547 women who had taken part in one of the 20 trials in which women were randomized to either tamoxifen or a placebo/observation. (In most of these trials the women took 5 years of tamoxifen, in some the took it for only 2 or 3 years.)

The researchers have been following these women for 15 years so that they could study the long-term effects of tamoxifen. The new analysis showed that during the first four years of tamoxifen use a woman’s risk of recurrence was reduced by 50 percent, and that during years 5 through 9 it was reduced by 30 percent, for an average recurrence rate reduction of 39 percent. (This means that if your chance of recurrence was 10 percent it would be reduced to about 6 percent).

The study found that after five years the absolute mortality difference was only 3 percent (9 percent in the tamoxifen group; 12 percent in the placebo group). By 10 years after stopping the drug (year 15), the absolute mortality difference was 9 percent (24 percent in the tamoxifen group; 33 percent in the placebo group.)  In other words it got better over time, even after the drug was stopped.

Most importantly, because the benefit has remained high over the past 13 years, this study tells us that for many women with ER-positive tumors, five years of tamoxifen not only reduces the risk of recurrence but also essentially cures the disease.

These findings should be reassuring to women who were on tamoxifen before the aromatase inhibitors (AIs) were developed. They should also be reassuring to women who switched from an AI to tamoxifen because of some of the common side effects associated with the AIs, like bone and joint pain. And they should be reassuring to premenopausal women for whom tamoxifen has remained the standard of care.

I think that this study may encourage more doctors to prescribe 2-3 years of tamoxifen to all women before they start on five years of an AI. It may also lead to more studies that look at whether five years of tamoxifen would be beneficial after five years of an AI.

These findings also point to the fact that we really don’t fully yet understand how tamoxifen works!

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13 Responses to Tamoxifen: The Benefits Continue

  1. Amy says:

    As a woman on Tamoxifen for exactly one week so far, I thank you for this update. It’s a strange thing to take a daily pill when you’ve been healthy (as far as you know) all your life. Glad to have some re-enforcement that it makes sense!

  2. Lori Murray says:

    I have been on an AI for one year. I had an oopherectomy so. I thought that was why I was not on tamoxofin. My understanding was that it took care of any remaining estrogen that may be in the body. Now you are saying that when I am finished with the five years I may be able to then go on tamoxofin?

  3. heske zelermyer says:

    Any studies about Tamoxifen and women with DCIS?

  4. Pam says:

    I think WAY TOO MANY women are on this drug. I refused it, I don’t take any drugs for prevention of breast cancer and I have been cancer free for 8 years! I had 2 lumpectomies, radiation and chemo and if I had to do it all over again, I would have eliminated the radiation too!(I had second and third degree burns from it!) I understand it is helpful for those with aggressive cancers, but most women would do just as well without it. I had invasive ductal cancer and I’m doing great!

    These studies should be taken with a grain of salt.A good statistician can make a study look good or bad, whichever he/she is paid to do. I worked in research for 7 years, I know exactly how the game is played.

    Like they say, if you don’t like what one study says, just wait, another one stating the opposite will come along before you know it.

  5. Sue says:

    I treated my Stage IIA breast cancer VERY aggressively, I thought my treatment plan was overkill…only to find out less than a year after completing chemotherapy the breast cancer metastasized into my bones. Anything and everything that can help prevent recurrence is important including Tamoxifen!

  6. Eileen Montgomery says:

    I just started tonight, my first pill of Tomixfen, Stage 1, no lymph nodes, and a tumor so small, less than 1cm. Estrogen positive. Six months after the lumpectomy I decided to give the tomixfen a try. Dont like the thought of a drug with its potential side effects, when is the best time to take this, morning or before bed?

  7. Nancy Machold says:

    My breast tumor was also Stage 1, no lymph node involvement and tumor size of 1 cm. I had radiation through Mammosite (no need for chemo). My oncologist prescribed Anastrozole instead of Tomixifen. My side effects were awful. . hot flashes, night sweats, fatigue and dizziness. I was told the A would reduce the chance of recurrence by 5%. After a few weeks of feeling awful I consulted with the MD and decided to stop taking it. I then turned to complementary treatment through Eastern practices of acupuncture and supplements. It’s only been 6 months since my lumpectomy, but all’s well so far. When I was taking it I took it at about 8 pm (2-3 hours before bedtime) so I could get to sleep and get a few good hours sleep before the flashes and sweats began at about 5 am.

  8. jwr3281 says:

    Indeed this is reassuring news. There may well be too many women who switch to an aromatase inhibitor after 5 years of tamoxifen. Even though it’s clear that there is added benefit, what seems to be overlooked is that women who even make it to the 5-year mark without a recurrence still have a low recurrence rate, whether or not they take an AI. I know the 5-year mark is often mistakenly referred to as “cured”, but it does seem to be that many women who go 5 years without recurrences have a scientifically justified reason to feel they are in the clear.

  9. Francine says:

    I’m 45 yrs. old and have recently had 2 biopsies that showed atypical ductal hyperplasia. My risk assessment has me rated at 2.8% risk currently. I will be monitored w/ mammos every 6 mos. The med. oncologist highly recommends that I begin taking Tamoxifen. I’m scared of the side effects. Any advice/insight is greatly appreciated!

  10. Donna Lanni says:

    I took arimidex for 5 years after a lumpectomy and radiation for Stage 1 breast cancer. A few months after my oncologist discontinued the arimidex, I was diagnosed with the same breast cancer, but in my skin. Subsequently I had a mastectomy of that same breast and ACT chemotherapy. I have been taking tamoxifen since March of 2011, and just found out the breast cancer is still in my breast. My treatment options are very limited now. I am receiving treatment from a world class facility and they hope to be able to do more radiation and further surgery. I am node negative so far..except for one intramammary node removed during the mastectomy. I may also receive some heat treatment. Are there any other new treatments or options for me? I have to say I can’t believe I am at this point, having been only stage 1 to begin with in 2005.

  11. Tina says:

    My mother had breast cancer and she died from this disease. I have had 2 biopsy’s both showing ductial epitheal hyperplasia. I chose to take the 5-year course of Tamoxifen and I had absolutely no side effects. In fact, it relieved all of my post-menopausal issues. I have been off of Tamoxifen for a year now and have had no issues. Tamoxifen gave me peace of mind and some assurance that I am challenging the disease before it challenges me. I feel that Tamoxifen therapy was an offensive decision. I’d rather play offense than defense any day.

  12. peaches says:

    Diagnosed with Stage 2B breast cancer and a bilateral mastectomy July 2011, I had additional lymph node removal which were all clear, the 6 chemo treatments, 33 radiation treatments, and I’ve been on Tamoxifen for 4 months, which I just recently quit taking. I’ve already had cortesone shots in 3 fingers from them locking up and had excrutiating pain. My other joints were beginning to lock up and ache. After having a bone density test, I was diagnosed with Osteopen, and now am taking Oscal-D twice daily. But, besides the headaches, and nausea, it literally felt like I was in a sauna every 15 minutes for 3 solid minutes. I was ready to pull my hair and teeth out. I’m gonna offer him my ovaries, but no more Tamoxifen. I’d rather take the chemo again.

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