Patients with breast cancer can stop tamoxifen after five yearsBMJ 2001; 322 doi: https://doi.org/10.1136/bmj.322.7295.1140 (Published 12 May 2001) Cite this as: BMJ 2001;322:1140
Women who have had breast cancer gain no benefit from taking tamoxifen for longer than five years, a new study has found.
The researchers randomly assigned 1172 women who had already taken tamoxifen for five years to continue taking either the drug or a placebo. For seven years after randomisation, a slight advantage was observed in women who discontinued tamoxifen compared with those who continued to receive it (disease-free survival 82% v 78%; P=0.03, relapse-free survival 94% v 92%; P=0.13).
The lack of benefit from additional tamoxifen therapy was independent of age or other characteristics (Journal of the National Cancer Institute 2001;93:684-90). The trial was run by the national surgical adjuvant breast and bowel project, which is based at the University of Pittsburgh in Pennsylvania.
Previously reported information from a randomised, placebo controlled clinical trial, carried out by the same project, showed that patients with oestrogen receptor positive breast cancer and negative axillary lymph nodes experienced a prolonged benefit from five years of tamoxifen therapy (Annals of Internal Medicine 1987;106:649-54).
Although results from smaller studies had shown that therapy for more than five years probably produced no additional benefits, until the current findings it has been unclear if longer administration produced additional benefit. “Until someone shows that there is a better benefit, then we have to live by these data,” said Dr Norman Wolmark of the national surgical adjuvant breast and bowel project.
The project has overseen many breast cancer studies that have resulted in setting standards of care. The question of how long patients should continue taking the drug is important because tamoxifen is not problem free. Even though the drug acts as an oestrogen antagonist in breast tissue, with prolonged use it is associated with uterine cancer. In the current study there were 12 cases of uterine cancer among women taking tamoxifen and six cases in the placebo group.
Dr Jeffrey Abrams of the cancer therapy evaluation programme at the National Cancer Institute, Bethesda, Maryland, wrote in an editorial in the same issue (pp 662-4) that the Pittsburgh study has provided valuable lessons in breast cancer treatment. However, Dr Abrams contended that the current data do not completely resolve the question of the duration of tamoxifen therapy.