Hormone Therapy
Oral Contraceptives
Obesity, Body Mass Index and Endometrial Cancer

Note: Separate PDQ summaries on Endometrial Cancer Screening; Endometrial Cancer Treatment; and Uterine Sarcoma Treatment are also available.

Based on solid evidence, giving progestin in combination with estrogen therapy eliminates the excess risk of endometrial cancer associated with unopposed estrogen among postmenopausal women who have a uterus and are taking hormone therapy.

Description of the Evidence

• Study Design: Evidence obtained from randomized controlled trials, cohort, and case-control studies.
• Internal Validity: Good.
• Consistency: Good.
• Magnitude of Effects on Health Outcomes: For women with a uterus, the risk of endometrial cancer associated with unopposed estrogen use for 5 or more years is more than tenfold higher compared with women not taking estrogen replacement therapy. The addition of progestin therapy to estrogen eliminates the risk of endometrial cancer. Based on data from the Women’s Health Initiative, the hazard ratio for endometrial cancer associated with combined hormone therapy, after an average follow-up of 5.6 years was 0.81 (95% confidence interval, 0.48–1.36) compared with women randomly assigned to placebo.
• External Validity: Good.

Based on solid evidence, the use of combination oral contraceptives (estrogen plus a progestin) is associated with a decreased risk of developing endometrial cancer.

Description of the Evidence

• Study Design: Evidence obtained from case-control and prospective studies.
• Internal Validity: Good.
• Consistency: Good.
• Magnitude of Effects on Health Outcomes: Oral contraceptive use is associated with a reduced risk of endometrial cancer ranging from 50% reduction associated with 4 years of use up to 72% reduction in risk with 12 or more years of use.
• External Validity: Fair.

There is inadequate evidence to determine if weight reduction alters the incidence of endometrial cancer.

Description of the Evidence

• Study Design: Evidence obtained from one cohort study.
• Internal Validity: Good.
• Consistency: N/A
• Magnitude of Effects on Health Outcomes: Intentional weight loss of 20 pounds or more was not associated with a statistically significant reduction in the incidence of endometrial cancer.
• External Validity: Fair.

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