Birth control pills, or oral contraceptives, are one of the most commonly taken prescription medications in women in our country. In addition to preventing pregnancy, there are other benefits to taking them. As with any medication there are side effects and risks as well. In recent years we have seen a lot of media attention on the risk of breast cancer associated with hormone replacement therapy, but there has not been very much on the risk of cancer with birth control use.
There have been many observational studies over the years trying to determine the effect of using OCs on overall cancer risk. When all types of cancer are combined there is a decrease in the overall cancer risk in women who have ever used OCs. This decrease is likely due to a substantial decrease in uterine and ovarian cancer in women who take the pill. Studies have consistently shown that using OCs decreases the risk of ovarian cancer. Overall the risk is one-third less for women who currently use or have used OCs in the past. What is most impressive is that the protection lasts for up to 30 years after stopping the pill and all doses of the pill provide the same protection. Uterine cancer is also decreased in women on OCs, the risk of uterine cancer while on the pill is almost half of what it would be off. The relative protection can last up to 15 years in some studies.
The effect of the pill on the risk of breast and cervical cancer is more controversial.
There may be an increase in cervical cancer in women who have taken OCs. Many studies show an increase in cervical cancer that continues as long as the pill is continued. When the pill is stopped, the risk returns to baseline levels. Interestingly, women who are negative for HPV (the virus most often associated with cervical cancer) do not have an increase in the risk when using OCs, leading to the conclusion that the pill may interact with the growth of HPV already present.
There have been several studies on the risk of breast cancer in OC users and the results are conflicting. Several population studies have been done and show no increase in the risk of breast cancer later in life for women who have taken OCs. The only study that showed an increase looked at women who took high dose OCs (in the 1970’s) AND had a strong family history of breast cancer. This may indicate that for women of average risk there is no significant increase, but in women who carry the BRCA1 or BRCA2 gene (or who have a strong family history-a mother or sister affected) the risk increases.
Overall, these risks and benefits likely balance out for women of average risk. In women with a family history of breast or ovarian cancer the circumstances may need to be discussed in more depth with a provider. It is important to remember that all these risks estimates are pretty low, not doubling or tripling risk. Another thing to keep in mind is that we increase and decrease our risks of cancer and other chronic diseases everyday, not just in medication choices, but in lifestyle choices as well.