Cancer Research Center of Hawaii study finds birth control pills reduce risk of ovarian cancer

Even short-term use of oral contraceptives effectively cuts cancer risk over decades

University of Hawaiʻi at Mānoa
Sharon Shigemasa, (808) 586-3011
Cancer Research Center of Hawaii
Pepi Nieva, (808) 275-3012
Bright Light Marketing
Posted: Jun 2, 2008

HONOLULU- Researchers at the Cancer Research Center of Hawai'i (CRCH)at the University of Hawaii at Manoa have found that oral contraceptives (OC) can protect women from the most common kind of ovarian cancer-epithelial, affecting cells on the outer surface of the ovary-even with short-term use. The results of their study were published in the March 2008 issue of the journal Epidemiology.

While the role of OC in reducing ovarian cancer risk has been proven by previous studies, this was the first time comprehensive information on time-related characteristics of contraceptive use-duration of use, recency of use, and age at initiation and cessation of use-was evaluated while accounting for formulation potency and age at first and last pregnancy. These are factors that may affect protective qualities of contraceptive hormones.

Using data collected in Hawai'i and Los Angeles from 813 women with ovarian cancer diagnosed in 1993-2006 and a control group of 992 women without cancer, researchers found that OC use reduces epithelial ovarian cancer risk after a short time since first use, has a long-lasting effect, and does not depend on the age of the user.

Although the protective effect was apparent after a short duration of OC use, longer use and the recency of use provided increased protection. A substantial reduction in ovarian cancer risk was observed among women who used OC for less than one year if they were recent users (defined as using the pill within the last 20 years). Women who used the pill for a year or more had reduced risk for at least three decades after they stopped use.

In recent OC users (five years or less) risk was 81 percent lower than in women who never used the pill, although differences were dependent on the formulation potency. The reduction in risk was 36 percent among women who stopped using the pill 20 or more years ago. On average, contraceptive use provided a 5 percent reduction in risk per year of use.

The mechanism for the protective influence of OC against epithelial ovarian cancer remains unclear. One hypothesis is that high levels of hormones during pregnancy and steroidal contraceptive use leads to the clearing of cancerous ovarian epithelial cells. This hypothesis, based on evidence for growth-regulating effects of steroid hormones, is supported by recent studies that have demonstrated enhanced ovarian cancer cell death in the presence of progesterone, a component of oral contraceptive pills.

Lead researchers for the study from the CRCH were Dr. Galina Lurie, Dr. Lynne Wilkens, and Dr. Marc Goodman of the CRCH Cancer Epidemiology program.

Community gynecological oncologists were Dr. Michael Carney and Dr. Keith Terada. The study was supported in part by the Department of Health and Human Services and the National Institutes of Health. Epithelial ovarian cancer cases were identified through the rapid-reporting systems of the CRCH Hawai'i Tumor Registry and the Los Angeles County Cancer Surveillance Program.

The Cancer Research Center of Hawai'i is one of only 63 National Cancer Institute-designated cancer centers throughout the United States. As a unit of the University of Hawai'i at Manoa, it conducts cancer research, educational activities, and community outreach, including the operation of the Hawai'i Tumor Registry, the Clinical Trials Unit, and the Cancer Information Service of Hawai'i.

The Center's research takes advantage of Hawai'i's ethnic and cultural diversity, geographic location, and unique environment to discover possible causes and cures for cancer. The Center is located at 1236 Lauhala Street in Honolulu. For general information on the Cancer Research Center of Hawai'i, please visit its website at

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