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Breast Cancer Prevention Studies
Key Points
• Breast cancer prevention studies are clinical trials involving
women who have not had cancer, but are at high risk of developing
the disease.
• In the Breast Cancer Prevention Trial (BCPT), the women
who received tamoxifen had a lower incidence of breast cancer
than the women who did not receive the drug. Results of
this study were published in 1998 (see Breast Cancer Prevention
Trial (BCPT) section).
• Another trial, the Study of Tamoxifen and Raloxifene (STAR),
is comparing raloxifene with tamoxifen. Results of this
study are expected in 2006 (see Study of Tamoxifen and Raloxifene
(STAR) section).
• The Capital Area SERM Study is testing raloxifene in premenopausal
women who are at high risk for breast cancer. A complete
report of the findings will be published early in 2005 (see
Capital Area SERM Study section).
• Other breast cancer prevention studies are in progress
(see Other Breast Cancer Prevention Studies section).
Breast cancer prevention studies are clinical trials (research
studies conducted with people) that explore ways of reducing
the risk, or chance, of developing breast cancer. Prevention
studies usually involve women who have not had breast cancer,
but are at high risk of developing the disease. Through
such studies, scientists hope to determine what steps are
effective in reducing the risk of breast cancer in women
of all races and ethnic backgrounds.
Most breast cancer prevention research is based on evidence
linking the development of this disease, in many cases,
with exposure to the hormone estrogen. The focus of several
recent breast cancer prevention studies has been on testing
the effectiveness of drugs called selective estrogen receptor
modulators (SERMs). SERMs are drugs that have some anti-estrogen
properties and some estrogen-like properties. Their anti-estrogen
activity may help reduce the risk of breast cancer by blocking
the effects of estrogen on breast tissue. Their estrogen-like
properties may help prevent the loss of bone density in
postmenopausal women; however, SERMs may cause bone loss
in premenopausal women.
The Breast Cancer Prevention Trial (BCPT)
The Breast Cancer Prevention Trial (BCPT) was funded by
the National Cancer Institute (NCI) and conducted by the
National Surgical Adjuvant Breast and Bowel Project (NSABP).
The BCPT was designed to see whether tamoxifen (Nolvadex®),
a SERM, can prevent breast cancer in women who are at an
increased risk of developing this disease. The study began
recruiting participants in April 1992 and closed enrollment
in September 1997. This study involved 13,388 premenopausal
and postmenopausal women at more than 300 centers across
the United States and Canada.
Results showed 49 percent fewer diagnoses of invasive breast
cancer in women who were randomized to take tamoxifen compared
with women who were randomized to take a placebo (an inactive
substance that looks the same as, and is administered in
the same way as, a drug in a clinical trial). Women on tamoxifen
also had 49 percent fewer diagnoses of noninvasive breast
tumors, such as ductal or lobular carcinoma in situ. Nine
women died of breast cancer, three women in the tamoxifen
group and six women in the placebo group (1).
In the BCPT, most of the side effects associated with tamoxifen
were temporary. However, there were some long-term risks,
including several serious health problems: endometrial cancer
(cancer of the lining of the uterus), uterine sarcoma (cancer
of the muscular wall of the uterus), pulmonary embolism
(blood clot in the lung), deep vein thrombosis (blood clot
in a large vein), and stroke. Because of these risks, women
taking tamoxifen should be monitored by their doctors for
any sign of serious side effects. All BCPT participants
have been asked to undergo regular follow-up examinations.
BCPT participants who were randomized to the tamoxifen group
and had not completed 5 years of tamoxifen therapy when
the study ended were given the opportunity to continue on
therapy. Postmenopausal women who had been taking the placebo
were invited to participate in another trial, the Study
of Tamoxifen and Raloxifene (STAR). (See the following section
for a description of this trial.) Women in the BCPT placebo
group also have the option of seeking tamoxifen from their
doctor.
The Study of Tamoxifen and Raloxifene (STAR)
The NSABP is conducting the Study of Tamoxifen and Raloxifene,
known as STAR. The study is funded primarily by the NCI.
The 19,000 participants are postmenopausal women who are
at least 35 years old and are at increased risk for developing
breast cancer. The study will determine how raloxifene (Evista®),
another SERM, compares with tamoxifen in reducing the incidence
of breast cancer in women who are at an increased risk of
developing the disease. As with tamoxifen, most of the known
side effects of raloxifene are temporary. However, like
tamoxifen, raloxifene increases the risk of pulmonary embolism
and deep vein thrombosis. STAR is closed to new participants,
and results are expected in the summer of 2006.
Capital Area SERM Study
The NCI is also conducting the Capital Area SERM Study to
evaluate the safety of raloxifene in premenopausal women
between the ages of 23 and 47 who are at increased risk
for breast cancer. Thirty-seven women enrolled in this study.
A complete report of the study’s findings will be published
in 2005.
Other Breast Cancer Prevention Studies
Drugs called aromatase inhibitors, which have been approved
by the U.S. Food and Drug Administration to treat hormone-sensitive
breast cancer, are being studied in clinical trials for
breast cancer prevention. These drugs interfere with the
adrenal enzyme aromatase, which is responsible for estrogen
production in postmenopausal women (2). The NCI is also
studying prevention options for women at high risk of breast
cancer that is not sensitive to hormones and can be more
difficult to treat than hormone-sensitive breast cancer.
More information about these and other clinical trials is
available from the NCI’s Cancer Information Service (CIS)
at 1–800–4–CANCER (1–800–422–6237) or by visiting the NCI’s
Web site at http://www.cancer.gov on the Internet.
Scientists are also studying the basic biology of breast
cancer to learn more about both non-hormone-sensitive and
hormone-sensitive tumors. This research may lead to better
ways of preventing all types of breast cancer.
NCI Priorities for Breast Cancer Prevention Research
Recognizing the impact of breast cancer on our society,
in 1997 the NCI convened a Breast Cancer Progress Review
Group (PRG) of experts and advocates to analyze the NCI’s
breast cancer research activities and develop recommendations
for the future. Based on its assessment of the status of
breast cancer research, the review group recommended research
priorities to accelerate progress in breast cancer prevention
and treatment. In August 1998, the group published its report,
Charting the Course: Priorities for Breast Cancer Research.
This report is available at http://prg.nci.nih.gov/breast/finalreport.html
on the Internet.
In October 2004, an internal NCI Breast Cancer Working Group
assessed the advances made since the release of the PRG
report. The Working Group released The NCI Breast Cancer
Progress Report, which documents trends in NCI’s breast
cancer research portfolio and the progress that has been
made in meeting the priorities identified by the PRG. The
report will help to guide the Institute as it moves forward
in breast cancer research. This report is available at http://prg.nci.nih.gov/breast/progress.html
on the Internet.
Estimating Breast Cancer Risk
Most breast cancer prevention trials involve
women at increased risk of developing this disease. For
example, it is clear that breast cancer occurs more often
in women over age 60. Other factors associated with increased
risk include a personal or family history of breast cancer
and changes in certain genes such as BRCA1 and BRCA2. Scientists
at the NCI and the NSABP have developed a computer program
(on CD-ROM) called the Breast Cancer Risk Assessment Tool.
This tool can help women and their health care providers
estimate a woman’s chances of developing breast cancer based
on several recognized risk factors. The Breast Cancer Risk
Assessment Tool also provides information on tamoxifen.
A copy of the CD may be ordered by calling the NCI’s CIS
at 1–800–4–CANCER (1–800–422–6237), or from the NCI Publications
Locator at http://www.cancer.gov/publications on the NCI’s
Web site.
Options for Women at Increased Risk
Doctors generally suggest that high-risk women be closely
monitored and have regular medical checkups so that, if
breast cancer develops, it is likely to be detected at an
early stage (3). These women may also consider participating
in prevention studies, taking tamoxifen, or undergoing preventive
surgery to reduce breast cancer risk. Preventive mastectomy
is surgery to remove one or both breasts in an effort to
prevent or reduce the risk of breast cancer (4). Existing
data suggest that preventive mastectomy may significantly
reduce (by about 90 percent) the chance of developing breast
cancer in moderate- and high-risk women (5). Other data
suggest that preventive oophorectomy (surgery to remove
the ovaries of women at high risk of ovarian cancer because
of BRCA1 or BRCA2 gene mutations) may reduce the risk of
breast cancer by about 50 percent (6).
The decision to join a study, take tamoxifen, or undergo
preventive surgery is an individual one. With any medical
procedure or intervention, both the benefits and the risks
of the therapy must be considered. The balance of these
factors will vary depending on a woman’s personal and family
health history and how she weighs the benefits and risks.
Women who are considering surgery or other steps to reduce
the risk of breast cancer should discuss their personal
risk factors with their doctor.
Selected References
1. Fisher B, Costantino JP, Wickerham DL, et al. Tamoxifen
for prevention of breast cancer: Report of the National
Surgical Adjuvant Breast and Bowel Project P–1 Study. Journal
of the National Cancer Institute 1998; 90(18):1371–1388.
2. Chlebowski RT, Col N, Winer EP, et al. American Society
of Clinical Oncology technology assessment of pharmacologic
interventions for breast cancer risk reduction including
tamoxifen, raloxifene, and aromatase inhibition. Journal
of Clinical Oncology 2002; 20(15):3328–3343.
3. Thull DL, Vogel VG. Recognition and management of hereditary
breast cancer syndromes. The Oncologist 2004; 9(1):13–24.
4. Stefanek M, Hartmann L, Nelson W. Risk-reduction mastectomy:
Clinical issues and research needs. Journal of the National
Cancer Institute 2001; 93(17):1297–1306.
5. Hartmann LC, Schaid DJ, Woods JE, et al. Efficacy of
bilateral prophylactic mastectomy in women with a family
history of breast cancer. New England Journal of Medicine
1999; 340(2):77–84.
6. Rebbeck TR, Lynch HT, Neuhausen SL, et al. Prophylactic
oophorectomy in carriers of BRCA1 or BRCA2 mutations. New
England Journal of Medicine 2002; 346(21): 1616–1622.
Related Resources
Publications (available at http://www.cancer.gov/publications)
National Cancer Institute Fact Sheet 4.19, The Study of
Tamoxifen and Raloxifene (STAR): Questions and Answers
• National Cancer Institute Fact Sheet 7.5, Preventive Mastectomy:
Questions and Answers
• National Cancer Institute Fact Sheet 7.16, Tamoxifen:
Questions and Answers
• Taking Part in Clinical Trials: Cancer Prevention Studies:
What Participants Need To Know
• What You Need To Know About™ Breast Cancer
National Cancer Institute (NCI) Resources
Cancer Information Service (toll-free)
Telephone: 1–800–4–CANCER (1–800–422–6237)
TTY: 1–800–332–8615
Online
NCI’s Web site: http://www.cancer.gov
LiveHelp, NCI’s live online assistance:
https://cissecure.nci.nih.gov/livehelp/welcome.asp
http://www.cancer.gov/
cancertopics/factsheet/
Prevention/breast-cancer
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