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Researchers from St. Luke’s-Roosevelt Hospital in New York have reported that 37% of women with estrogen receptor-positive localized breast cancer are not compliant with prescribed tamoxifen (Nolvadex®), resulting in a higher rate of recurrent disease. The details of this study were published in the October, 2008 issue of the American Journal of Surgery.[[1]]( "_ednref1")

A majority of breast cancers are estrogen receptor–positive (ER-positive), meaning they are stimulated to grow by the female hormone estrogen. Depriving ER-positive breast cancers of estrogen can slow their growth. Tamoxifen is an anti-estrogen that has long been the mainstay of hormone therapy for breast cancer. Several randomized studies have shown that treatment with tamoxifen for five or more years significantly reduces the risk of breast cancer recurrence.

Despite this proven efficacy, some studies have shown that compliance to tamoxifen is less than optimal. In one U.S. study of women over the age of 65, compliance to tamoxifen for five years was 69%.[[2]]( "_ednref2") A Swiss study revealed a similar compliance rate of 67%.[[3]]( "_ednref3")

In the current study, researchers compared the outcomes of breast cancer patients who were compliant to recommended radiation, chemotherapy, or hormonal therapy (tamoxifen) with the outcomes of those who were not compliant. They wanted to determine first, what the level of compliance was and second, the impact this compliance had on recurrence rates.

The researchers found that 7% of patients were not compliant with recommended chemotherapy treatment and 4% of patients were not compliant with the recommended radiation treatment. In startling contrast, 37% of patients did not comply with the recommended adjuvant hormonal therapy treatment of tamoxifen. Noncompliance with tamoxifen was associated with an 87% survival, compared with 96% for compliant women. In other words, women who are compliant with hormonal therapy are significantly more likely to survive longer without a recurrence.

The researchers concluded that noncompliance with tamoxifen is common and results in significantly increased risk of recurrence. More study is needed into the reasons for noncompliance. In this particular study, older age was associated with noncompliance to radiation and chemotherapy, but younger women tended to be noncompliant with tamoxifen. As physicians and researchers gain an understanding of why patients fail to comply with the prescribed hormonal therapy regimen, they may be able to address these issues in order to improve compliance and as a result, improve survival rates.

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[[1]]( "_edn1") Ma AMT, Barone J, Wallis AE, et al. Noncompliance with adjuvant radiation, chemotherapy, or hormonal therapy in breast cancer patients. American Journal of Surgery. 2008;196:500-504.

[[2]]( "_edn2") Lash TL, Fox MP, Westrup JC, et al. Adherence to tamoxifen over the five-year course. Breast Cancer Research Treatment. 2006;00:215-220.

[[3]]( "_edn3") Guth U, huang DJ, Schotzau A, et al. Target and reality of adjuvant endocrine therapy in postmeopausal patients with invasive breast cancer. British Journal of Cancer. 2008;99:428-433.

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