Posted by: bcconnections | December 14, 2012

Longer Duration of Tamoxifen Therapy Shows Benefit

For women with estrogen receptor-positive breast cancer, treatment with 5 years of tamoxifen is known to substantially reduce the risk of breast cancer recurrence and breast cancer mortality.  Results of the international Adjuvant Tamoxifen:  Longer Against Shorter (ATLAS) trial, reported recently at the San Antonio Breast Cancer Symposium and published online in The Lancet demonstrate that extending tamoxifen therapy to 10 years results in a further reduction in breast cancer recurrence and mortality.

The ATLAS trial recruited 12,894 women with early-stage breast cancer who completed 5 years of tamoxifen therapy and randomized them to either 5 additional years or no further treatment.  Of these women, 6,846 had estrogen receptor-positive disease.  After following these women for 10 years, the investigators reported their breast cancer outcomes and side effects.

Women who took tamoxifen for 10 years were 3.7% less likely to have their breast cancer recur compared to the women who took Tamoxifen for 5 years (617 recurrences versus 711).  They were also 2.8% less likely to die from breast cancer (331 deaths versus 397).  However, extended treatment with tamoxifen increased the incidence of endometrial cancer from 1.6% in the control group to 3.1% in the treatment group.  This translated into a slight increase in endometrial cancer-related death, from 0.2% in the control group to 0.4% in the treatment group.

Results from the ATLAS trial are expected to impact the clinical care of some women with estrogen receptor-positive breast cancer.  According to Dr. Peter Ravdin, director of the Comprehensive Breast Health Clinic at the University of Texas Health Science Center, the finding from ATLAS “will have a major immediate impact on premenopausal women” who are at high risk for recurrence.  Ten years of tamoxifen may not provide much benefit to women with small, slow-growing cancers and negative lymph nodes, since their risk of recurrence is already quite low.  While post-menopausal women were included in the ATLAS trial, it is unlikely that these findings will change their standard of care since most post-menopausal women are prescribed aromatase inhibitors (AIs, i.e. Arimidex, Aromasin or Femara) and not tamoxifen.  There is currently no data to support the idea that 10 years of an AI is better than 5 years of an AI, although ongoing clinical trials seek to address this question.

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