Two Years of Tamoxifen After Surgery Offers Long-Term Survival Benefits

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After surgery and other treatments (chemotherapy, radiation therapy), women diagnosed with early-stage, hormone-receptor-positive breast cancer usually take 5 to 10 years of a hormonal therapy medicine to lower recurrence risk (the cancer coming back). When hormonal therapy is used this way, it's called adjuvant hormonal therapy.

Of the adjuvant hormonal therapy choices, tamoxifen has been approved the longest and is approved to treat both premenopausal and postmenopausal women. The aromatase inhibitors are the other main type of hormonal therapy medicine and are approved to treat only postmenopausal women.

While most women take tamoxifen for 5 or 10 years, it hasn’t been clear if taking tamoxifen for fewer than 5 years offered benefits.

A Swedish study suggests that taking tamoxifen for 2 years offers long-term survival benefits for premenopausal women diagnosed with early-stage, estrogen-receptor-positive disease compared to no treatment after surgery.

The study was published online on May 9, 2016 by the Journal of Clinical Oncology. Read “Two Years of Adjuvant Tamoxifen Provides a Survival Benefit Compared With No Systemic Treatment in Premenopausal Patients With Primary Breast Cancer: Long-Term Follow-Up (> 25 years) of the Phase III SBII:2pre Trial.”

In the study, the researchers randomly assigned 564 premenopausal women diagnosed with stage II breast cancer to one of two treatments after surgery:

  • 2 years of tamoxifen (276 women)
  • no hormonal therapy (288 women)

One woman in the tamoxifen group and six women in the no hormonal therapy group were treated with chemotherapy.

The women were diagnosed between 1984 and 1991. The women ranged in age from 25 to 58. The women were followed for about 26 years.

During the follow-up period:

  • tamoxifen group: 117 women died from breast cancer; 25 women died from other causes
  • no hormonal therapy group: 145 women died from breast cancer; 27 women died from other causes

Overall, women treated with tamoxifen had slightly better survival, no matter the hormone receptor status of the cancer.

For women diagnosed with estrogen-receptor-positive cancer, treatment with tamoxifen:

  • slightly reduced the risk of dying from any cause
  • reduced the risk of dying from breast cancer by 27%

The reduction in risk of dying from breast cancer was statistically significant, which means that it was likely because of the tamoxifen treatment and not just due to chance.

Women diagnosed with estrogen-receptor-positive disease who were younger than 40 got the most benefits from tamoxifen.

Two years of tamoxifen seemed to offer the most survival benefit 5 to 15 years after diagnosis, but continued to offer some benefit more than 15 years after diagnosis.

Tamoxifen didn’t reduce the risk that women diagnosed with hormone-receptor-negative breast cancer would die from breast cancer.

These very positive results show that the benefits of tamoxifen are long-lasting.

Like most breast cancer treatments, tamoxifen can cause side effects, including hot flashes and night sweats. In some cases, tamoxifen may cause serious side effects, such as blood clots.

While the side effects of tamoxifen can be bothersome, they’re overshadowed by the reality that hormone-receptor-positive breast cancer can come back. Hormonal therapy after surgery reduces that risk. If you’ve been prescribed hormonal therapy after surgery, you must remember this.

There are good ways to get rid of any obstacles stopping you from doing all you can to lower your recurrence risk. If side effects are a major problem for you, talk to your doctor about ways to manage them. You also may be able to switch to a different hormonal therapy.

For more information, visit the Breastcancer.org pages on Staying on Track With Treatment. 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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