New analysis confirms OC's protective effects

Good news for your patients who use oral contraceptives (OCs): A new analysis of 45 epidemiological studies shows that use of such pills during a woman's lifetime gives substantial long-term protection against ovarian cancer.1

Researchers looked at data from 23,257 women with ovarian cancer, 7,308 (31%) of whom had ever used OCs, and 87,303 women without ovarian cancer, of which 32,717 (37%) had ever used the Pill. In women with ovarian cancer, mean age of diagnosis was 56 years. Those who had used contraceptives had done so for an average of 4.4 years in the ovarian cancer group and 5.0 years in the control group.

The researchers found that the Pill's protection against ovarian cancer persisted for more than 30 years after oral contraceptive use had ceased, but became somewhat attenuated over time. The proportional risk reductions per five years of use were 29% [95% confidence interval (CI) 23-34%)] for use that had ceased less than 10 years previously, 19% (14%-24%) for use that had ceased 10-19 years previously, and 15% (9%-21%) for use that had ceased 20-29 years previously. The analysis findings indicate the longer OCs were used, the greater the protection.

What does this mean for women in the United States? According to the researchers' estimates, in high-income countries, using oral contraceptives for 10 years reduces the risk of developing ovarian cancer before age 75 from 12 down to eight per 1,000 women and lowers the risk of death from ovarian cancer before age 75 from seven down to five per 1,000 women.

Worldwide, the Pill already has prevented 200,000 women from developing cancer of the ovary and has prevented 100,000 deaths from the disease, notes Valerie Beral, MD, director of the Cancer Research UK Epidemiology Unit at Oxford (England) University and lead author of the analysis. "More than 100 million women are now taking the Pill, so the number of ovarian cancers prevented will rise over the next few decades to about 30,000 per year," states Beral.

Does dose matter?

Check the pill formulations offered in your clinic's formulary: Chances are that there are few, if any, pills with a 50 mcg dose of estrogen.

Estrogen doses in oral contraceptives have decreased significantly over the years. Preparations in the 1960s typically contained more than double the estrogen dose of preparations in the 1980s. Despite the variations in pill formulations, the current analysis found no apparent variation in the relative risk of ovarian cancer between women whose oral contraceptive use was during the 1960s, 1970s, or 1980s.

Researchers also found that risk reduction did not vary substantially by women's ethnicity, education, age of menarche, family history of breast cancer, use of hormone replacement therapy, body mass index, height, or consumption of alcohol or tobacco.

Pill offers protection

In the United States, about one-fifth (19%) of women ages 15-44, and about one-third (32%) of those ages 20-24, use the Pill.2 What does the analysis's findings mean for your patients? Since oral contraceptives help to prevent ovarian malignancy in high- as well as low-risk women, consider Pill use in women at elevated risk for ovarian cancer, including low-parity women and those with a positive family history, says Andrew Kaunitz, MD, professor and associate chair in the Obstetrics and Gynecology Department at the University of Florida College of Medicine — Jacksonville.

An accompanying editorial published with the analysis questions whether OCs should be provided over the counter, given their protective benefits. Eduardo Franco, MPH, DrPH, professor of epidemiology and oncology director of the Division of Cancer Epidemiology at McGill University in Montreal, Quebec, says providing OCs is a great opportunity for health care providers to give women other health promotion messages that are crucial for them, such as providing cervical cancer screening and tobacco cessation aids. Allowing women to obtain the Pill over the counter would remove this opportunity, says Franco, who co-authored a comment for the current analysis.3

"We now know that OCs are safer than what we painted them to be and as such we should make them available without the hesitations of the past," Franco states. "However, if we consider the underprivileged populations in Latin America and Africa, we must keep in mind the totality of benefits that seeing a provider will bring to these women."

References

  1. Collaborative Group on Epidemiologic Studies of Ovarian Cancer. Ovarian cancer and oral contraceptives: collaborative reanalysis of data from 45 epidemiological studies including 23,257 women with ovarian cancer and 87,303 controls. Lancet 2008; 371:303-314.
  2. Chandra A, Martinez GM, Mosher WD, et al. Fertility, family planning, and reproductive health of U.S. women: Data from the 2002 National Survey of Family Growth. Vital Health Stat 2005; 23:1-160.
  3. Franco EL, Duarte-Franco E. Ovarian cancer and oral contraceptives. Lancet 2008; 371:277-278.