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Hormone Therapy Cessation Linked to Breast Cancer Reduction

January 03, 2011
Lebanon, NH

Tracy Onega, PhD

Significant new study also links hormone therapy to DCIS

An analysis of more than 2 million mammograms of more than 700,000 American women shows, for the first time, a direct link between the reduction in use of hormone therapy (HT) and declining rates of ductal carcinoma in situ (DCIS, considered to be the earliest form of breast cancer), in addition to the earlier reports for invasive breast cancer. The study's authors, including Tracy Onega, PhD, a member of the Cancer Control research program at Dartmouth-Hitchcock Norris Cotton Cancer Center, believe the evidence compellingly suggests that hormone use promotes breast tumor growth.

Dr. Onega is director of the New Hampshire Mammography Network (NHMN), which has been collecting mammography data for 15 years, and contributed mammograms to the study for analysis. The NHMN is one of seven breast cancer registries comprising the Breast Cancer Surveillance Consortium, which is an ongoing effort to improve understanding of breast cancer screening practices in the United States and their relation to changes in stage at diagnosis, survival, or breast cancer mortality. The BCSC is funded and coordinated by the Applied Research Program of the National Cancer Institute's Division of Cancer Control and Population Sciences.

"The study supports the conclusion that consistent use of hormone therapy in women is a tumor-promoter in some cases," commented Dr. Onega. "We also show the impact of hormone therapy on DCIS. What we're seeing is that hormone therapy promotes breast density, which can be a factor in the development and promotion of breast cancer."

HT was a common prescription for pain relief in post-menopausal women, although use of HT has been in sharp decline since 2002, when the first large-scale randomized trial suggesting a link between hormone use by women and the development of breast cancer was published. The new study provides much more evidence of such a link.

The study, "Changes in Invasive Breast Cancer and Ductal Carcinoma In Situ Rates in Relation to the Decline in Hormone Therapy Use," published in the Dec. 10, 2010, issue of the Journal of Clinical Oncology, reviewed 2,071,814 mammogram screenings performed between January 1997 and December 2008 on 696,385 women aged 40 to 79 years. Analysis of the screenings revealed clear patterns: women aged 50 to 69 years had the highest levels of hormone use and also the biggest reduction in invasive breast cancer when they stopped HT. Rates of DCIS also declined in the same age group after HT ceased. By comparison, breast cancer rates did not decline among women aged 40 to 49 years, who were less likely than older women to have used HT.

NHMN's continuing collection of data helps gauge the impact of mammography on cancer detection. The data gathered by the registry also helps with the evaluation of new mammography technologies. Since the late 1990s, NHMN has collected data on almost a million mammograms in New Hampshire. The combined data from the seven registries, including NHMN's, contains information about more than 7.5 million mammograms, making the BCSC a critical research resource for studies designed to assess the delivery and quality of breast cancer screening and related patient outcomes in the United States.

"What we're trying to do, ultimately, in analyzing the impact of HT on rates of breast cancer development is create the evidence base to help women make informed decisions about hormone therapy," said Dr. Onega. "The NHMN is a crucial part of this effort. It's a very significant registry, and we are proud that it is based here in New Hampshire, and of the involvement of New Hampshire women and radiologists."

About Dartmouth-Hitchcock Norris Cotton Cancer Center

Norris Cotton Cancer Center combines advanced cancer research at Dartmouth College and Dartmouth Medical School with patient-centered cancer care provided at Dartmouth-Hitchcock Medical Center, at Dartmouth-Hitchcock regional locations in Manchester and Keene, NH, and St. Johnsbury, Vt., and at 11 partner hospitals throughout New Hampshire and Vermont. It is one of 40 centers nationwide to earn the National Cancer Institute's "Comprehensive Cancer Center" designation. Learn more about Norris Cotton Cancer Center research, programs, and clinical trials online at

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