Chemoprevention of breast cancer: A joint guideline from the Canadian
Task Force on Preventive Health Care and the Canadian Breast
Cancer Initiative's Steering Committee on Clinical Practice Guidelines
for the Care and Treatment of Breast Cancer
[06/12/2001; Canadian Medical Association Journal]
Objective: To assist women and their physicians in making decisions
regarding the prevention of breast cancer with tamoxifen and
Women at low or normal risk of breast cancer (Gail risk assessment
index <1.66% at 5 years): There is fair evidence to recommend
against the use of tamoxifen to reduce the risk of breast cancer
in women at low or normal risk of the disease (grade D recommendation).
Women at higher risk of breast cancer (Gail index 1.66% at 5 years):
Evidence supports counselling women at high risk on the potential
benefits and harms of breast cancer prevention with tamoxifen
(grade B recommendation). The cutoff for defining high risk is
arbitrary, but the National Surgical Adjuvant Breast and Bowel
Project P-1 Study included women with a 5-year projected risk
of at least 1.66% according to the Gail index, and the average
risk of patients entered in the trial was 3.2%.
Examples of high-risk
clinical situations are 2 first-degree relatives with breast
cancer, a history of lobular carcinoma in situ or a history of
atypical hyperplasia. As the risk of breast cancer increases
above 5% and the benefits outweigh the harms, a woman may choose
to take tamoxifen.
The duration of tamoxifen use in such situations
is 5 years based on the results from trials of tamoxifen involving
women with early breast cancer. If a woman raises concerns or
has already been evaluated and is calculated to be at high risk,
then individuals experienced and skilled in counselling may discuss
the potential benefits and harms of tamoxifen use.
Important additional issues:
Prevention of breast cancer with raloxifene: Current evidence
does not support recommending chemoprevention of breast cancer
with raloxifene outside of a clinical trial setting.
Screening using the Gail risk assessment index: This index was
the main eligibility criterion for enrolling women in the one
study that showed potential benefit from chemoprevention.
it has not been evaluated for use as a routine screening or case-finding
instrument; validation of the index is required. Overall, current
evidence does not support a shift to its routine use in physicians'
offices for screening or case finding. However, when a woman
or her physician is concerned about the woman's increased risk
of breast cancer, the index can be a useful tool in deciding
whether to pursue an in-depth discussion of the potential benefits
and harms of chemoprevention.
Hence, the approach to identifying
women at higher risk who warrant counselling and shared decision-making
will vary across practices. (The risk assessment index is available
Validation: The authors' original text was revised by both the
Canadian Task Force on Preventive Health Care and the Steering
Committee on Clinical Practice Guidelines for the Care and Treatment
of Breast Cancer. The final document reflects a consensus of
Committee on Safety of
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