© 2001 by Oxford University Press
Journal of the National Cancer Institute, Vol. 93, No. 13, 961,
July 4, 2001
© 2001 Oxford University Press
MEMORANDUM FOR: Science Writers and Editors on the Journal Press List
Tamoxifen Therapy for Breast Cancer Reported to Increase Risk of Estrogen Receptor-Negative Tumors in the Contralateral Breast
June 28, 2001 (EMBARGOED FOR RELEASE 4 P.M. EDT July 3)
A new study shows that giving tamoxifen to women with breast cancer decreases their risk of developing cancer in the contralateral (opposite) breast that is estrogen receptor (ER) positive, but it possibly increases their risk of developing an ER-negative tumor. Nevertheless, an accompanying editorial questions the conclusions and raises the question of whether these findings can be translated into clinical practice.
The findings are presented by Christopher Li, M.D., M.P.H., and colleagues at the Fred Hutchinson Cancer Research Center, Seattle, in the July 4 issue of the Journal of the National Cancer Institute. They report that, among women who developed ER-positive contralateral breast tumors, 47 women had taken tamoxifen and 65 had not. Among women who developed ER-negative contralateral breast tumors, 17 women had taken tamoxifen and three had not. They calculated that, compared with women who did not receive tamoxifen, women receiving tamoxifen had a hazard ratio of 0.8 of developing an ER-positive contralateral tumor, but they had a hazard ratio of 4.9 of developing an ER-negative contralateral tumor.
The authors extracted data from a population-based tumor registry, which contained information for women diagnosed with a primary invasive cancer in one breast between 1990 and 1998. These women were followed until cancer developed in the other breast, they died from any cause, or until the study ended in December 1999. The analysis was restricted to women who were at least 50 years old and whose first breast cancer had a localized or regional stage.
The study population involved 4,654 women who were classified as users of tamoxifen, and 4,327 women who were classified as nonusers of tamoxifen. Eighty-nine tamoxifen users developed cancer in the second breast, compared with 100 for the nonusers of tamoxifen. When the data were further analyzed according to ER status, which was available for 132 women whose status was determined by the immunohistochemical technique, the increased risk of developing an ER-negative cancer in the contralateral breast was revealed.
The authors conclude that their findings are of potential clinical and public health importance given the poorer prognosis that women with ER-negative breast tumors have compared with women with ER-positive tumors. However, they state that further studies are required to confirm their findings and to evaluate the survival of women who develop contra-lateral breast cancer according to their prior use of tamoxifen and the ER status of their tumors.
In an editorial, Sandra Swain, M.D., says that the results presented by Li et al. are inconsistent with other data in the literature. She notes that the study has noteworthy limitations—it is a retrospective analysis that assesses a treatment effect when treatment was not randomly assigned, the authors were not able to collect information on how long women took tamoxifen, and it includes only a small number of events upon which to draw conclusions. Consequently, she believes the study does not provide reliable evidence that is sufficient to make any conclusions regarding the ER status of contralateral breast cancer in women treated with tamoxifen. However, she notes that this study does point out correctly that the determination of ER status of contralateral breast cancers is important and that it is the first study in which attempts were made to evaluate this issue in a large number of patients.
Contact: Kristen Woodward, Fred Hutchinson Cancer Research Center, (206) 667-5095; fax: (206) 667-7005; kwoodwar{at}fhcrc.org. Editorial: NCI Press Office, (301) 496-6641; fax: (301) 496-0846. (Note: The media contact is the NCI Press Office because the author is on the NCI staff.)
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Li CI, Malone KE, Weiss NS, Daling JR. Tamoxifen therapy for primary breast cancer and risk of contralateral breast cancer. J Natl Cancer Inst 2001;93:1008–13.
Editorial: Swain SM. Tamoxifen and contralateral breast cancer: the other side. J Natl Cancer Inst 2001;93:963–5.
Note: This memo to reporters is from the Journal staff and is not an official release of the National Cancer Institute (NCI) or Oxford University Press (OUP) nor does it reflect NCI or OUP policy. In addition, unless otherwise stated, all articles and items published in the Journal reflect the individual views of the authors and not necessarily the official points of view held by NCI, any other component of the U.S. government, OUP, or the organizations with which the authors are affiliated. Neither NCI nor any other component of the U.S. government nor OUP assumes any responsibility for the completeness of the articles or other items or the accuracy of the conclusions reached therein.
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