Women who develop ovarian cancer are more likely to have better outcomes if they took oral contraceptives prior to their diagnosis, according to a new study by researchers at Mayo Clinic.
In an analysis that examined outcomes of patients treated at Mayo Clinic between 2000 and 2013, investigators found that those who had taken birth control pills prior to their cancer diagnosis had improved progression-free survival (PFS) and length of time that they lived with the disease without it worsening compared with those who had not taken contraceptives.
“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,” lead author Aminah Jatoi, an oncologist at Mayo Clinic, said in a statement. “However, few studies have explored the connection between the pill and outcomes in patients who ultimately develop the disease.”
For the study, which was published in BMC Cancer, researchers evaluated 1,398 patients using questionnaires and data extracted from electronic medical records. Of the 1,398 patients, 827 responded that they had previously taken oral contraceptives. The patient-reported median duration of birth control use was 60 months.
The investigators used two type of analyses — univariate analyses, where oral contraceptive use was the main variable, and multivariate analyses, which considered cancer stage, histology, tumor grade, outcome of initial surgery, chemotherapy after surgery, age at diagnosis, smoking history and family history.
The univariate analyses found that birth control use was associated with better overall survival and better PFS. In the multivariate analyses, there was a statistically significant association between oral contraceptive use and improved PFS, but not overall survival (OS). The authors theorize that this could be because older patients who passed away may have died from non–cancer-related causes.
In these models, patient age was a confounding factor because younger age was significantly associated with contraceptive use. After adjusting for age in the multivariate analyses, OS lost its statistical significance, but improved PFS continued to be associated with prior contraceptive use.
The authors proposed a couple of hypotheses to explain why contraceptives would lead to better health outcomes in patients with ovarian cancer. One theory suggests that by halting ovulation, contraceptives protect against the monthly trauma on the surface of the ovary, which can develop DNA mutations and subsequent carcinogenesis.
“Although this line of thinking may contradict the hypothesis that ovarian cancer originates from fallopian tube fimbria, it nonetheless merits consideration, particularly because the fimbria are also exposed to hormones in the follicular fluid,” the authors note.
In addition, preclinical research found that exposure to birth control hormones decreased matrix metalloproteinase-2 activity. The authors theorized that the matrix metalloproteinase-2 proteins may modify the extracellular matrix to have long-term consequences for reducing the potential of developing ovarian cancer and providing greater susceptibility to treatment.
The authors concluded that investigations of mechanisms are needed in order to develop effective therapeutic interventions for patients with ovarian cancer.
“Without question, further studies are needed in this area,” Jatoi said, “but our study might provide a sense of hope for patients who are struggling with ovarian cancer.”
Jatoi A, Foster NR, Kalli KR, et al. Prior oral contraceptive use in ovarian cancer patients: assessing associations with overall and progression-free survival. BMC Cancer. 2015; doi: 10.1186/s12885-015-1774-z.