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Side Effects More Severe in Women Taking Hormonal Therapy After Breast Cancer Surgery

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After surgery, women diagnosed with hormone-receptor-positive breast cancer usually take hormonal therapy medicine to reduce the risk of the cancer coming back (recurrence). Hormonal therapy medicines work in two ways:

  • by lowering the amount of estrogen in the body
  • by blocking the action of estrogen on breast cancer cells

Doctors call treatment given after surgery adjuvant treatment.

There are several types of hormonal therapy medicines. Tamoxifen, a selective estrogen receptor modulator (SERM), is one of the most well-known. Tamoxifen can be used to treat both premenopausal and postmenopausal women. The aromatase inhibitors:

  • Arimidex (chemical name: anastrozole)
  • Aromasin (chemical name: exemestane)
  • Femara (chemical name: letrozole)

have been shown to be more effective at reducing recurrence risk in postmenopausal women and are now used more often than tamoxifen to treat women who’ve gone through menopause. Aromatase inhibitors aren’t used to reduce recurrence risk in premenopausal women.

Side Effects

Both tamoxifen and aromatase inhibitors can cause side effects. Tamoxifen may cause hot flashes and increase the risk of blood clots and stroke. Aromatase inhibitors may cause muscle and joint aches and pains. Less common but more severe side effects of aromatase inhibitors are heart problems, osteoporosis, and broken bones. Research has shown that about 25% of women who are prescribed hormonal therapy to reduce the risk of recurrence after surgery either don’t start taking the medicine or stop taking it early.

A study has found that compared to women who didn’t take hormonal therapy after surgery, women who did take hormonal therapy had more severe symptoms such as hot flashes, joint pain, and vaginal dryness.

The study was published online on Jan. 19, 2016 by the Journal of Clinical Oncology. Read the abstract of “Impact of Adjuvant Endocrine Therapy on Quality of Life and Symptoms: Observational Data Over 12 Months From the Mind-Body Study.”

Patricia Ganz, M.D., medical oncologist and professor of medicine and public health at the University of California, Los Angeles, was the lead author of the study. Dr. Ganz also is a member of the Professional Advisory Board.

In the Mind-Body Study, the researchers wanted to compare the quality of life of women diagnosed with early-stage (stage 0, I, II, or IIIA) breast cancer who took hormonal therapy after surgery to similar diagnosed women who didn’t take hormonal therapy after surgery.

The study included 186 women ages 21 to 65 from the Los Angeles area diagnosed with early-stage disease between 2007 and 2010.

The women’s quality of life, cognitive function, and symptoms were assessed three times during the study:

  • before starting hormonal therapy, if prescribed
  • 6 months later
  • 12 months later

The assessments included questionnaires, neuropsychological testing, and blood tests.

Overall, about 66% of the women started hormonal therapy:

  • 66 women took tamoxifen
  • 60 women took an aromatase inhibitor
  • 60 women didn’t take hormonal therapy

Between 35% and 50% of the women in each treatment group also had chemotherapy and radiation. Between 7% and 18% of the women in each group also had only chemotherapy, and between 27% and 38% in each group also had only radiation.

At the first assessment, all three treatment groups had similar symptoms, including hot flashes, fatigue, sleep problems, and depression. The severity of the symptoms also was similar. Compared to the average woman, the women in the study had worse quality of life.

At 12 months after starting hormonal therapy, if prescribed, the researchers found differences in symptoms and symptom severity between the three treatment groups:

  • Women taking hormonal therapy had more severe hot flashes compared to women not taking hormonal therapy.
  • Women taking an aromatase inhibitor had more severe joint or bone pain than women not taking hormonal therapy; this pain got worse over time in women taking an aromatase inhibitor and stayed the same in women taking tamoxifen and women not taking hormonal therapy.
  • Women taking hormonal therapy reported more cognitive problems than women not taking hormonal therapy. Over time, reports of cognitive problems declined in women not taking hormonal therapy, but stayed about the same in women taking hormonal therapy.
  • Women taking an aromatase inhibitor reported that vaginal dryness got worse over time, while women taking tamoxifen reported that vaginal dryness improved somewhat over time.
  • Women taking tamoxifen said their weight problems got worse over time, while this issue stayed about the same in women taking an aromatase inhibitor and women not taking hormonal therapy.
  • Women taking tamoxifen reported an increase in bladder control problems over time, while this issue stayed about the same in women taking an aromatase inhibitor and women not taking hormonal therapy.

Women who also had chemotherapy were more likely to have:

  • cognitive problems
  • arm problems
  • hot flashes
  • joint pain
  • vaginal dryness
  • depression
  • fatigue
  • problems sleeping

Older women were more likely to have:

  • bladder control problems
  • hot flashes
  • vaginal dryness

The researchers noted that many of the symptoms linked to hormonal therapy overlap with chemotherapy side effects. Still, the women who weren’t taking hormonal therapy saw many of these side effects ease over time, suggesting that chemotherapy contributes to the severity of hormonal therapy side effects, as well as how long these side effects last.

If you’ve been diagnosed with hormone-receptor-positive, early-stage breast cancer and will be taking hormonal therapy after surgery, it’s very important that you take the medicine for as long as it’s prescribed. Hormone-receptor-positive breast cancer can come back and hormonal therapy after surgery reduces that risk -- you must remember that.

Side effects caused by hormonal therapy can be very troublesome for many women. It’s important to talk to your doctor as soon as you start having any symptoms, including hot flashes, trouble sleeping, joint or bone pain, fatigue, or difficulty concentrating. Don’t wait until the symptoms are intolerable and you have to stop taking the medicine. There are steps you can take to ease these side effects, including switching to a different type of hormonal therapy.

For more information, visit the Staying on Track With Treatment pages. You can read about why it’s so important to stick to your treatment plan, as well as ways to manage side effects after radiation, chemotherapy, and hormonal therapy. If you’re taking hormonal therapy after surgery now, stick with it as prescribed. If you’re thinking of stopping early, talk to your doctor first. Together, you can find a solution that is best for you.

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