A new follow-up study led by the Early Breast Cancer Trialists s Collaborative Group shows that treatment of estrogen receptor-positive breast cancer with tamoxifen for five years reduces annual breast cancer mortality by 30 percent, compared to a placebo and the effects have now been shown to last for at least 15 years after starting use of the drug.
In their study just published in The Lancet, researchers updated their previous meta-analysis of over 10,000 women with estrogen-receptor-positive breast cancer across 20 randomized trials and found that cancer recurrence rates decreased by 47 percent with tamoxifen compared to a placebo after four years of follow-up, and by 32 percent after treatment of between five and nine years. All-cause mortality also showed sustained reductions associated with tamoxifen use and, in an accompanying editorial, Dr. Stephen K. Chia of the British Columbia Cancer Agency in Vancouver and Dr. Antonio C. Wolff of Johns Hopkins said the results of the study suggest that tamoxifen may be a treatment that potentially cures many [breast cancer] patients.
While aromatase inhibitors have also been recommended for use by post-menopausal women during adjuvant treatment (treatment that modifies another treatment) of hormone-receptor positive breast cancer, there is not enough long-term data on the efficacy of their use compared to tamoxifen.
Approved about 30 years ago, tamoxifen had previously been linked to an increased risk of uterine cancer and pulmonary embolism, says ACSH's Dr. Gilbert Ross. But the new study shows no significant increased risk associated with tamoxifen use in women under age 55, which is good news, since physicians were previously reluctant to prescribe this drug to pre-memopausal women unless they had had a hysterectomy.
The study results demonstrate that the benefits of tamoxifen extend beyond its active treatment, says ACSH s Dr. Ruth Kava. But she warns that, even though it s relatively safe to take, it is certainly not risk-free.
