ROCHESTER, Minn., Nov. 11 (UPI) -- Women with ovarian cancer who have used oral contraceptives at some point in their lives have better health outcomes than those who have not used them, according to a new study by the Mayo Clinic.
Researchers said they're unclear on why women who have taken birth control pills fare better if they get the cancer, but believe the effect is related to the prevention of ovulation. By reducing monthly changes to ovaries as they release eggs, researchers think the risk of DNA mutations is reduced, resulting in less aggressive forms of cancer.
Previous studies have shown that for every five years a woman takes oral contraceptives, her risk for ovarian cancer decreases by 20 percent, with a stronger association of lower risk for the disease among women who have used the pill for 10 years or more at any point in their lives.
"Multiple studies from a variety of sources have indicated that oral contraceptives are associated with a reduced risk of ovarian cancer, one of the most deadly cancers in women," says Dr. Aminah Jatoi, an oncologist at Mayo Clinic, in a press release. "However, few studies have explored the connection between the pill and outcomes in patients who ultimately develop the disease."
Researchers surveyed 1,398 ovarian cancer patients treated at Mayo Clinic in Minnesota between 2000 and 2013, all patients at least 20 years old, performing two types of analysis on the data they collected.
Of the patients, 571 reported they hadn't used oral contraceptives. The rest of the patients used the pill for a median duration of 60 months, with a range among participants of 1 to 444 months.
The first analysis found patients who'd used the pill had improved survival without progression of the cancer and improved levels of overall survival compared to patients who'd never used it.
The second analysis found a statistically significant association between birth control pill use and progression-free survival, but not overall survival. Researchers suggest the weaker link to overall survival in the second analysis is connected to older patients who may have died from non-cancer-related causes.
The study is published in BMC Cancer.