Find Information About:

Drugs & Supplements

Get information and reviews on prescription drugs, over-the-counter medications, vitamins, and supplements. Search by name or medical condition.

Pill Identifier
WebMD

Pill Identifier

Having trouble identifying your pills?

Enter the shape, color, or imprint of your prescription or OTC drug. Our pill identification tool will display pictures that you can compare to your pill.

Get Started
My Medicine
WebMD

My Medicine

Save your medicine, check interactions, sign up for FDA alerts, create family profiles and more.

Get Started

WebMD Health Experts and Community

Talk to health experts and other people like you in WebMD's Communities. It's a safe forum where you can create or participate in support groups and discussions about health topics that interest you.

  • Second Opinion
    WebMD

    Second Opinion

    Read expert perspectives on popular health topics.

  • Community
    WebMD

    Community

    Connect with people like you, and get expert guidance on living a healthy life.

Got a health question? Get answers provided by leading organizations, doctors, and experts.

Get Answers

Sign up to receive WebMD's award-winning content delivered to your inbox.

Sign Up

Breast Cancer Health Center

Font Size
A
A
A

Overview

continued...

Magnitude of Effect: The RR of breast cancer is decreased 4.3% for every 12 months of breast-feeding, in addition to 7% for each birth.[3]

Study Design: Case-control and cohort studies.
Internal Validity: Good.
Consistency: Good.
External Validity: Good.

Exercise

Based on solid evidence, exercising strenuously for more than 4 hours per week is associated with reduced breast cancer risk.

Magnitude of Effect: Average RR reduction is 30% to 40%. The effect may be greatest for premenopausal women of normal or low body weight.

Study Design: Prospective observational and case-control studies.
Internal Validity: Good.
Consistency: Good.
External Validity: Good.

Estrogen use by women with prior hysterectomy

Benefits

Based on fair evidence, women who have undergone a prior hysterectomy and who are treated with conjugated equine estrogen have a lower incidence of breast cancer. However, epidemiological studies yield conflicting results.

Magnitude of effect: After 6.8 years, incidence was 23% lower in women treated with estrogen in an RCT (0.27% per year, with a median of 5.9 years of use, compared with 0.35% per year among those taking a placebo), but was 30% higher in women treated with estrogen in an observational study. The difference in these results may be explained by different screening behavior by the women in both studies.

Study Design: One RCT, observational studies.
Internal Validity: Fair.
Consistency: Poor.
External Validity: Poor.

Harms

Based on solid evidence, women who have undergone hysterectomy and who are taking postmenopausal estrogen have an increased risk of stroke and total cardiovascular disease.

Magnitude of Effect: There is a 39% increase in the incidence of stroke (RR, 1.39; 95% CI, 1.1-1.77) and a 12% increase in cardiovascular disease (RR, 1.12; 95% CI, 1.01-1.24).

Study Design: RCTs, observational studies.
Internal Validity: Good.
Consistency: Good.
External Validity: Poor.

Interventions With Adequate Evidence of Decreased Risk of Breast Cancer

Selective estrogen receptor modulators (SERMs)

Benefits

Based on solid evidence, tamoxifen and raloxifene reduce the incidence of breast cancer in postmenopausal women, and tamoxifen reduces the risk of breast cancer in high-risk premenopausal women. The effects observed for tamoxifen and raloxifene show persistence several years after active treatment is discontinued, with longer duration of effect noted for tamoxifen than for raloxifene.[4]

1 | 2 | 3 | 4 | 5 | 6

Today on WebMD

Breast Cancer Overview
From self-exams and biopsies to reconstruction, we’ve got you covered.
Dealing with breast cancer
Get answers to your questions.
 
woman having mammogram
Experts don’t agree on all fronts, but you can be your own advocate.
woman undergoing breast cancer test
Many women worry. But the truth? Most abnormalities aren’t breast cancer.
 
Breast Cancer Treatments Improving
VIDEO
Resolved To Quit Smoking
SLIDESHOW
 
Woman getting mammogram
Article
Screening Tests for Women
SLIDESHOW
 
ovarian cancer overview slideshow
SLIDESHOW
serious woman
Article
 
what is your cancer risk
HEALTH CHECK
10 Ways to Revitalize Slideshow
SLIDESHOW