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

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

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

    Second Opinion

    Read expert perspectives on popular health topics.

  • 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

Colorectal Cancer Health Center

Font Size

Colorectal Cancer Prevention (PDQ®): Prevention - Health Professional Information [NCI] - Overview



Based on solid evidence, harms of ASA use include excessive bleeding, including gastrointestinal bleeds and hemorrhagic stroke.

Magnitude of Effect: The estimated average excess risk of upper gastrointestinal complications is 10 to 30 per 1,000 people for a period of 10 years, on the higher end for men and on the lower end for women. Risk increases with age.

Study Design: Evidence obtained from large databases.[15,20]
Internal Validity: Good.
Consistency: Good.
External Validity: Good, data from national databases.

Hormone therapy (estrogen plus progestin)

Based on solid evidence, combined hormone therapy (conjugated equine estrogen and progestin) decreases the incidence of invasive CRC.[21]

Based on fair evidence, combination conjugated equine estrogen and progestin has little or no benefit in reducing mortality from CRC. Data from the Women's Health Initiative (WHI), a randomized, placebo-controlled trial evaluating estrogen plus progestin, with a mean intervention of 5.6 years and a follow-up of 11.6 years showed that women taking combined hormone therapy had a statistically significant higher stage of cancer (regional and distant) at diagnosis but not a statistically significant number of deaths from CRC compared with women taking the placebo.[21]

Magnitude of Effect: There were fewer CRCs in the combined hormone therapy group than in the placebo group (0.12% vs. 0.16%; HR = 0.72; 95% CI, 0.56-0.94). A meta-analysis of cohort studies observed a RR of 0.86 (95% CI, 0.76-0.97) for incidence of CRC associated with combined hormone therapy.

There were 37 CRC deaths in the combined hormone therapy arm compared with 27 deaths in the placebo arm (0.04% vs. 0.03%; HR 1.29; 95% CI, 0.78-2.11).

  • Study Design: Randomized controlled trial and cohort studies
  • Internal Validity: Good.
  • Consistency: Good for effect on incidence; N/A for effect on mortality; results were based on one trial.
  • External Validity: Good.

Estrogen-only therapy


Based on fair evidence, conjugated equine estrogens do not affect the incidence of, or survival from, invasive CRC.[22]

Magnitude of Effect: N/A.

Study Design: One randomized controlled trial.
Internal Validity: Good.
Consistency: N/A.
External Validity: Good.
Next Article:

Today on WebMD

Colorectal cancer cells
The right diagnosis is the most important factor.
man with a doctor
Our health check will steer you in the right direction.
sauteed cherry tomatoes
Fight cancer one plate at a time.
bladder cancer x-ray
Do you know the warning signs?
Colon vs Rectal Cancer
New Colorectal Treatments
can lack of sleep affect your immune system
Cancer Facts Quiz
Virtual Colonoscopy
Picture of the Colon
Vitamin D