Many Women Stop Taking Tamoxifen

Cancer Connect

According to the results of a study conducted in Ireland, many women who begin taking tamoxifen (Nolvadex®) for the adjuvant treatment of breast cancer discontinue use (without switching to another hormonal therapy) before completing five years of treatment. These results were published in the journal Cancer.

Each year breast cancer is diagnosed in over 200,000 women in the U.S. alone. Many of these breast cancers will be hormone receptor-positive, meaning that they are stimulated to grow by the circulating female hormones estrogen or progesterone.

Treatment of hormone receptor-positive breast cancer often involves hormonal therapies that suppress or block the action of estrogen. These therapies include tamoxifen as well as agents known as aromatase inhibitors. Tamoxifen acts by blocking estrogen receptors, whereas aromatase inhibitors suppress the production of estrogen.

For women treated with hormonal therapy, five years of treatment is commonly recommended. Because shorter durations of treatment may reduce treatment effectiveness, compliance with medication recommendations is important.

To explore how frequently women discontinue tamoxifen during the initial years of treatment, researchers in Ireland conducted a study among more than 2,800 women who began taking tamoxifen between 2001 and 2004. Women were followed for up to three and a half years.

Tamoxifen discontinuation was defined as six months without tamoxifen and with no alternative hormonal therapy.

  • By one year 22% of women had discontinued tamoxifen without switching to another hormonal therapy.
  • By three and a half years, 35% of women had discontinued tamoxifen without switching to another hormonal therapy.
  • Compared to women between the ages of 45 and 54, younger women (ages 35 to 44) and older women (over age 75) were more likely to discontinue tamoxifen. Higher rates of discontinuation were also observed among women with previous antidepressant use, and among women with Parkinson disease or dementia.

The researchers conclude that early discontinuation of tamoxifen may be more common than has previously been reported. Because early discontinuation of tamoxifen and other oral anticancer drugs may have a negative impact on risk of cancer recurrence or mortality, the researchers recommend the development of strategies to improve medication adherence.

Reference: Barron TI, Connolly R, Bennett K, Feely J, Kennedy MJ. Early discontinuation of tamoxifen: a lession for oncologists. Cancer [early online publication]. January 22, 2007.

Related News:Tamoxifen Appears to Prevent Breast Cancer Years Following Completion of Therapy(1/2/2007)

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