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Ovarian Cancer Prevention (PDQ®)

Health Professional Version
Last Modified: 06/20/2014

Overview

Factors With Adequate Evidence of Increased Risk of Ovarian Cancer
        Hormone replacement therapy
        Perineal talc exposure
        Obesity, weight gain and height
Factors With Adequate Evidence for a Decreased Risk of Ovarian Cancer
        Oral contraceptives
        Tubal ligation
        Breast-feeding
        Risk-reducing bilateral salpingo-oophorectomy
Areas of Uncertainty
        Ovarian hyperstimulation for infertility treatment

Note: Separate PDQ summaries on Ovarian Cancer Screening and Ovarian Epithelial Cancer Treatment are also available.

Factors With Adequate Evidence of Increased Risk of Ovarian Cancer

Hormone replacement therapy

Based on fair evidence, current or recent hormone therapy is associated with a small increased risk of ovarian cancer. Risks attenuate after hormone therapy is discontinued. Risk may be stronger with estrogen-only therapy compared with combined estrogen-progestin therapy.

Magnitude of Effect: Modest with observed relative risks (RRs) of 1.20 to 1.8.

Study Design: One randomized clinical trial, cohort and case-control studies.
Internal Validity: Good.
Consistency: Fair.
External Validity: Good.
Perineal talc exposure

Based on solid evidence, perineal application of talc is associated with a small increased risk of ovarian cancer. The International Agency for Research on Cancer has concluded that perineal talc is a possible carcinogen.[1]

Magnitude of Effect: Odds ratio of 1.24 (95% confidence interval [CI], 1.15-1.33).

Study Design: Cohort and case-control studies.
Internal Validity: Good.
Consistency: Good.
External Validity: Good.
Obesity, weight gain and height

Based on fair evidence, obesity, weight gain, and height are associated with a modest increased risk of ovarian cancer.

Magnitude of Effect: Based on an overview analysis of 25,157 women with ovarian cancer and 81,211 women without ovarian cancer from 47 epidemiological studies, the RR of ovarian cancer per 5 cm increase in height is 1.07 (95% CI, 1.05–1.09). The RR of ovarian cancer per 5 kg/m2 increase in body mass index is 1.10 (95% CI, 1.07–1.13) among never-users of hormone therapy and 0.95 (95% CI, 0.92–0.99) among ever-users of hormone therapy.[2]

Study Design: Cohort and case-control studies.
Internal Validity: Good.
Consistency: Good.
External Validity: Good.
Factors With Adequate Evidence for a Decreased Risk of Ovarian Cancer

Oral contraceptives

Benefits

Based on solid evidence, oral contraceptive use is associated with a decreased risk of developing ovarian cancer.

Magnitude of Effect: The degree of risk reduction varies by duration of oral contraceptive use and time since last use. For 1 to 4 years of oral contraceptive use the RR reduction is 22%, and for 15 or more years of use the RR reduction is 56%. The reduction in risk persisted for over 30 years after use was discontinued but the degree of reduction attenuates over time. The risk reduction per 5 years of use was 29% for women who discontinued use less than 10 years ago and decreased to 15% for women who discontinued use 20 to 29 years ago. Ten years of use reduced cancer incidence before age 75 years from 1.2 to 0.8 per 100 users and mortality from 0.7 to 0.5 per 100 users. The number needed to treat for 5 years was estimated to be about 185 women.

Study Design: Multiple case-control and cohort studies; meta-analyses.
Internal Validity: Good.
Consistency: Good.
External Validity: Good.

Harms

Based on solid evidence, combined current use of estrogen-progestin oral contraceptive use is associated with an increased risk of venous thromboembolism. Oral contraceptives are not associated with a long-term increased risk of breast cancer but may be associated with a short-term increased risk while a woman is taking oral contraceptives. The risk of breast cancer declines with time since last use.

Magnitude of Effect: The risks may vary by preparation. Overall, the absolute risk of venous thromboembolism is about three events per 10,000 women per year while taking oral contraceptives. The risk is modified by smoking. Breast cancer risk among long-term (>10 years) current users is estimated at one extra case per year per 100,000 women. The risk dissipates with time since last use.

Study Design: Observational studies.
Internal Validity: Good.
Consistency: Good.
External Validity: Good.
Tubal ligation

Benefits

Based on solid evidence, tubal ligation is associated with a decreased risk of ovarian cancer.

Magnitude of Effect: A relative reduction in the odds of developing ovarian cancer, adjusting for other forms of contraception, of about 30% has been observed.

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

Harms

Based on fair evidence, harms include surgical risks, including the following:

  • Damage to the bowel, bladder, or major blood vessels requiring unintended surgery (rate of 0.9 per 100 procedures).
  • Febrile morbidity (rate of 0.1 per 100 procedures).
  • Rehospitalization (rate of 0.6 per 100 procedures) because of complications such as infection, vaginal bleeding, or pain.
  • Transfusion (rate of <0.01 per 100 procedures based on one event).
  • In one large study of outcomes, one life-threatening event of anaphylaxis was reported (rate of <0.01 per 100 procedures).
  • Incomplete ligation may result in pregnancy following the procedure, with a risk from 1 in 100 to 1 in 200 procedures.
Study Design: One prospective cohort study.
Internal Validity: Good.
Consistency: N/A.
External Validity: Fair.
Breast-feeding

Based on solid evidence, breast-feeding is associated with a decreased risk of ovarian cancer.

Magnitude of Effect: 8% decrease with every 5 months of breast-feeding.

  • Study Design: Multiple case-control and cohort studies; meta-analysis.
  • Internal Validity: Good.
  • Consistency: Good.
  • External Validity: Good.
Risk-reducing bilateral salpingo-oophorectomy

Benefits

Based on solid evidence, risk-reducing bilateral salpingo-oophorectomy is associated with a decreased risk of ovarian cancer. Peritoneal carcinomatosis has been reported following surgery. Risk-reducing surgery is generally reserved for women at high risk of developing ovarian cancer, such as women who have an inherited susceptibility to ovarian cancer.

Magnitude of Effect: 90% reduction in risk of ovarian cancer observed among women with a BRCA1 or BRCA2 mutation.

Study Design: Multiple case-control studies.
Internal Validity: Good.
Consistency: Good.
External Validity: Good.

Harms

Based on solid evidence, prophylactic oophorectomy among women who are still menstruating at the time of surgery is associated with infertility, vasomotor symptoms, decreased sexual interest, vaginal dryness, urinary frequency, decreased bone mineral density, and increased cardiovascular disease.

Magnitude of Effect: Reported prevalence of vasomotor symptoms varies from 41% to 61.4% among women who underwent oophorectomy before natural menopause. Women with bilateral oophorectomy who did not take hormone therapy were twice as likely to have moderate or severe hot flashes compared with women who underwent natural menopause. The RR of cardiovascular disease among women with bilateral oophorectomy and early menopause was 4.55 (95% CI, 2.56–9.01).

Study Design: Cohort and case-control studies.
Internal Validity: Good.
Consistency: Good.
External Validity: Good.
Areas of Uncertainty

Ovarian hyperstimulation for infertility treatment

Evidence is poor to determine the association between ovarian hyperstimulation and the risk of ovarian cancer. Risk of borderline ovarian tumors may be increased among subfertile women treated with in vitro fertilization. Risk of ovarian cancer may be increased among women who remain nulligravid after being treated with ovarian stimulating medications.

Magnitude of Effect: Uncertain—risk of invasive ovarian cancer may be increased among women who remain nulligravid after treatment; risk of borderline ovarian tumors may be increased among women treated with infertility drugs.

Study Design: Cohort and case-control studies; systematic review.
Internal Validity: Fair.
Consistency: Poor.
External Validity: Fair.
References
  1. IARC Working Group on the Evaluation of Carcinogenic Risks to Humans: Carbon black, titanium dioxide, and talc. IARC Monogr Eval Carcinog Risks Hum 93: 1-413, 2010.  [PUBMED Abstract]

  2. Collaborative Group on Epidemiological Studies of Ovarian Cancer: Ovarian cancer and body size: individual participant meta-analysis including 25,157 women with ovarian cancer from 47 epidemiological studies. PLoS Med 9 (4): e1001200, 2012.  [PUBMED Abstract]