Tamoxifen: What you Need to Know

Tamoxifen: What you Need to Know

Marian Barnick

Marian Barnick

Marian Barnick is a Registered Kinesiologist and Cancer Movement Therapist teaching cancer patients how to move better and feel better.

Tamoxifen: What You Need to Know

In my blog post last week I talked about tamoxifen which is being prescribed for certain types of breast cancers.  Because it’s become a pretty mainstream therapy AND because it’s surrounded with some controversy, I thought we should dive a little deeper on the topic of tamoxifen and take a look at what it’s for, why it’s prescribed, as well as the pros and cons.  With this knowledge, you’ll be able to make an informed decision and have a great conversation with your Oncologist if this is one of the treatments offered to you.


There are many different ways to treat cancer and we’re most familiar with surgery, chemotherapy and radiation.  Treatment goals can vary, depending on the stage of cancer, location of cancer, and a lot of other variables.

Sometimes a tumor can’t be operated on immediately so treatment is given before surgery with the goal of shrinking the tumor.  Other times treatment is given after surgery, especially if surgery couldn’t remove all of the tumor or the cancer has spread.  Other treatment goals include trying to reduce the risk of cancer returning after the tumor is removed.

Targeted Therapy

Targeted therapy is one type of treatment that is used to reduce the risk of cancer recurrence.

Targeted therapy is a type of cancer treatment that works on specific cells that cancer needs to grow and spread.  Drugs have been developed that target these specific cells.  When these specific cells aren’t available or can’t bind with the cancer cells, the cancer cells aren’t able to grow and therefore can’t spread.

In order to see what type of cells are within your tumor, a biopsy is done.  Your Oncologist will review the biopsy results and can then determine if there is a targeted therapy that works on your specific type of tumor.

A biopsy is the same procedure that’s used to determine if breast cancer tumors are hormone receptor positive or hormone receptor negative.  Hormone receptor positive breast cancer are tumors that have estrogen or progesterone receptors (or both).  This type of breast cancer accounts for 70% to 75% of all invasive breast cancer cases.

There is a special type of targeted therapy that works on receptor positive breast cancers.  Because the identified target in this type of breast cancer is a hormone, the targeted therapy that’s used is called Hormone Therapy.

Hormone Therapy

Hormone therapy for breast cancer works by either lowering the estrogen in your body or blocking the estrogen from attaching to the cancer cells.  Either way, the goal is the same which is to limit the hormone that’s required by the cancer cells to grow.

Hormone therapy may also be prescribed if cancer cells have returned or spread to other parts of the body as well as to decrease the risk of recurrence.

Hormone therapy is generally used with other forms of treatment such as surgery and chemotherapy but as I outlined last week, it can be prescribed on its own.  The specific hormone therapy we’re discussing is tamoxifen and its target is estrogen.


As I mentioned, up to 75% of invasive breast cancer is hormone positive so tamoxifen is prescribed to a large number of breast cancer patients.  Tamoxifen can be prescribed to patients who have any stage of breast cancer and the goals of treatment can be different depending on the stage.

The usual prescription is one pill, daily, for five years.  However, sometimes hormone therapies can lose their effectiveness as cancer cells become resistant to them.  Therefore, other types of treatment may need to be prescribed.

Recent studies show that there are increased benefits with patients taking tamoxifen for 10 years.

There’s been great data to show decreases in recurrence for women using tamoxifen as an adjuvant therapy – after their main type of treatment is completed.

Tamoxifen can also be prescribed as neo-adjuvant therapy – before surgery   with the goal of shrinking the tumor.  With a smaller tumor, surgery can be less invasive and reduce the amount of tissue that is taken from the breast.

Tamoxifen can be prescribed to women who are premenopausal or postmenopausal.

If you are postmenopausal and taking menopause hormone therapy (MHT) you will probably be asked to stop this treatment.

Tamoxifen has been prescribed to women who are at high risk of developing breast cancer as a treatment to prevent breast cancer.

Some anti-depressant medications can interfere with tamoxifen treatment.

Benefits of Tamoxifen

Tamoxifen is prescribed because it has been proven to reduce the risk of cancer returning.

The National Cancer Institute funded a large study in 1998.  The results showed a 50 percent reduction in both invasive and non-invasive breast cancer in women treated with tamoxifen.

Tamoxifen has been shown to shrink tumors before surgery to allow for less invasive surgeries.

Tamoxifen has been shown to improve survival rates for hormone receptor positive breast cancer patients.

Possible Side Effects of Tamoxifen

The controversy of course comes from weighing the benefits and the side effects.  Although tamoxifen works by decreasing the availability of estrogen to breast tissue, tamoxifen can act just like estrogen to other cells in the body and this can increase some risk factors.

As with any drug, some side effects are more common and some are rare.  The big picture is to know as much as you can so you can make an informed choice that’s right for you.

It’s important to note that some studies have shown that the length of treatment, age of the patient, and whether she is premenopausal or postmenopausal have an affect on the types of side effects.

Side effects can include:

  • hot flashes
  • fatigue
  • vaginal dryness
  • mood swings
  • nausea
  • headache
  • constipation
  • leg swelling

The risk is low but there is an increased risk for endometrial cancer, deep vein thrombosis (DVT), and stroke.  If cancer has spread to the bones, there can be pain and swelling in joints and muscles called tumor flares.  Tamoxifen may affect fertility and patients are advised to avoid pregnancy while taking tamoxifen.

Of particular concern to premenopausal women is the risk of bone loss or osteopenia (which can lead to osteoporosis).  Therefore, your doctor may order a bone density test as well as blood work before starting tamoxifen and during treatment for a comparison.  If there is bone loss while on treatment, there are other medications that may be prescribed to help boost your bone density like bisphosphonates.

Interesting to note is that tamoxifen can work in just the opposite way in postmenopausal women and help to strengthen bones.  Postmenopausal women prescribed aromatase inhibitors instead of or after tamoxifen can have an increased risk of bone loss.

Exercising and Tamoxifen

The other thing you doctor will specifically recommend whether you’re premenopausal or postmenopausal is an exercise program that includes weight bearing exercise (like walking) as well as working with weights to help your bones stay strong.  Research shows that cancer patients who exercise as compared to the control groups who don’t exercise benefited by NOT having bone loss, which was seen in the control group, and by actually improving their level of bone mineral density.

Aside from the bone benefits, exercise will also help with fatigue that may be a side effect from tamoxifen and your overall mood.  Remember too, studies are showing a decrease risk of cancer recurrence with those patients who exercise.  So whether or not you are taking tamoxifen, exercise has benefits to help you as well.


National Cancer Institute
ACSM Guide to Exercise and Cancer Survivorship


Share on facebook
Share on pinterest
Share on twitter
Share on linkedin

Leave a Reply

Close Menu