Study: Hormonal birth control may reduce ovarian cancer risk in people with BRCA mutations

Study findings

This study included 3,466 participants. Researchers compared birth control use among participants with a BRCA1 or BRCA2 mutation who were diagnosed with ovarian cancer (1,733 cases) to those with a BRCA1 or BRCA2 mutation who had never had ovarian cancer (1,733 controls).

Among all participants, 1,741 used some form of hormonal birth control. Most (97%) took birth control pills:

• 1,687 took birth control pills.
• 64 women used any type of IUD for birth control. 48 used hormonal IUD.
• 30 women used an implant for birth control.
• 12 women used injections for birth control.

Hormonal birth control was linked to reduced ovarian cancer.

• Among women who used any type of hormonal birth control, the risk of ovarian cancer was reduced by 38% compared to women who never used hormonal birth control.
  
  Projected change in lifetime ovarian cancer risk with a 38% reduction in lifetime risk is shown in the graph below.
  
   
• People who took birth control bills had reduced ovarian cancer.
  • The use of birth control pills reduced ovarian cancer risk by 34%.
    • This was statistically significant.
    • This reduction in risk is similar to the results of other studies.
• People using longer acting birth control (implants, injections or IUDs) tended to have ovarian cancer less often but this was not statistically significant.
  • The use of implants reduced ovarian cancer risk by 70%.
    • This was not statistically significant. This may be because only a few people in the study used implants (30 of 1741)
  • The use of injections reduced ovarian cancer risk by 63%.
    • This was not statistically significant. This may be because only a few people in the study used injections (12 of 1741).
  • IUD use was associated with a small reduction in ovarian cancer risk.
    • This finding was not statistically significant. This may be because only a few people in the study used IUDs (64 of 1741).

Participants who did not develop ovarian cancer were more likely to:

• have breastfed their children. This is in line with other research we covered here.
• have slightly more children (on average).
• have had a tubal ligation (had their tubes tied).  

Strengths and limitations

Strengths:

• Participants with ovarian cancer were matched to participants who did not have ovarian cancer, by the year they entered the study, birth year, country of residence, BRCA mutation type and breast cancer history.
• The study enrolled a large number of participants and followed them for about 20 years.

Limitations:

• Relatively few people used forms of birth control other than birth control pills. While participants who used implants, injections and IUDs to decrease risk had a lower risk for ovarian cancer, these results should be viewed with caution due to the low number of people who used these forms of birth control.
• The information on participants’ cancer history and birth control use was self-reported, so it is possible some of the information was inaccurate.
• Because the number of people who used long-acting forms of birth control was small,  further study is required to assess how these contraceptives may reduce ovarian cancer risk.

Context

Using birth control pills can reduce the risk of ovarian cancer in the general population. This study shows that using birth control pills also decreases ovarian cancer risk in people with a BRCA mutation. It also offers new data that for high-risk people, birth control injections, implants and IUDs may also offer protection against ovarian cancer. However, because the number of people in this study who relied on these methods of birth control was small, more research is needed.