Long-term Use of Oral Contraceptives Protects Against Deadliest Forms of Ovarian Cancer, Large Study Finds

Long-term use of oral contraceptives protects women from the most lethal types of ovarian cancers, a large multi-center study has found.

The study, “Oral contraceptive use and risk of highly fatal ovarian cancer: Evidence from the Ovarian Cancer Association Consortium,” was recently presented at the 2019 American Association for Cancer Research Annual Meeting, held March 29 to April 3, in Atlanta, Georgia.

Prior studies have shown that use of oral contraceptives (i.e. birth control) is associated with a decrease in the risk of ovarian cancer. However, it is unknown whether oral contraceptives play a role in preventing aggressive and fatal ovarian cancers.

To investigate this, researchers at the Roswell Park Comprehensive Cancer Center and University of Buffalo used data from the Ovarian Cancer Association Consortium (OCAC) to evaluate the association between the pre-diagnostic use of oral contraceptives and the development of highly fatal ovarian cancer, which is defined as death within 12 to 18 months of diagnosis.

Researchers evaluated data from 20 case-control studies that participated in the OCAC, which included 579 women who died within 12 months of their diagnosis and 1,294 patients who died within 18 months of diagnosis. The patients in the 12-month cohort were matched to 2,279 healthy controls, and patients in the 18-month cohort were matched to 5,095 controls.

Results indicated that, even after adjusting for age, site of cancer, and parity (number of births), oral contraceptive use was associated with a 46% reduction in the risk of death within 12 months of diagnosis of highly fatal ovarian cancer.

Additionally, there was a significant trend towards a reduced risk of highly fatal ovarian cancer with longer duration of oral contraceptive use. In fact, researchers found that women who used oral contraceptives for more than 10 years experienced a 66% reduction in odds of death within 12 months of diagnosis, but no significant benefits were seen among patients who used oral contraceptives for one year or less.

“The longer the history of oral contraceptive use, the greater the protection we observed in terms of reduced chance of dying from aggressive ovarian cancer,” Jennifer Mongiovi, first author of the study, said in a press release.

The researchers also showed that use of oral contraceptives was most protective for patients with the endometrioid subtype of ovarian cancer.

“For every five years of use, we observed 32% lower odds of highly fatal disease, compared to 13% for all ovarian cancer as previously reported by other researchers. This association also varies by histological subtype, and was found most protective for highly fatal endometrioid ovarian cancers,” added Mongiovi.

“These results are in line with current evidence that has demonstrated a substantial decrease in risk of ovarian cancer with (oral contraceptive) use for five or more years,” the investigators wrote.

They added that future research should be aimed at understanding why there is an association between use of oral contraceptives and ovarian cancer, and to determine which specific subpopulations of ovarian cancer patients would most benefit from this “chemopreventive strategy.”