Oral contraceptives linked to cancer


Researchers said the correlation between oral contraceptive use and breast cancer were also influenced by age and time.

Photo credit: Fotosearch

What you need to know:

  • Researchers find high likelihood of breast cancer.
  • Study records minimal risk of endometrial and ovarian cancers.
  • Older women were more likely to become at risk of getting the cancers.

You are at risk of getting cancer if you use oral contraceptives, a new study has shown. 

In the study carried out by the American Association for Cancer Research, breast cancer was found to be highly likely to be triggered by oral contraceptives especially after stoppage of use.

“We saw an increased hazard of breast cancer, primarily after oral contraceptive discontinuation. An association that rapidly declined towards null, and no difference in cumulative breast cancer risk was seen when participants were followed up on until 2019,” said the study.

But, the researchers said the correlation between oral contraceptive use and breast cancer were also influenced by age and time.

“We have a much longer follow up compared to most previous studies, clearly indicating that oral contraceptive use gives a protective effect against ovarian and endometrial cancers up to 30-35 years after discontinuation,” says the study.

Live births

The analysis, conducted between 2006 and 2010 and a follow up until 2019, looked into data from about 256,661 women users and those who had not used oral contraceptives born between 1939 and 1970.

A total of 82 per cent of the women who were part of the study had used (some were still using) oral contraceptives, while 18 per cent had not used that form of contraception.

The researchers estimated the use of oral contraception by documenting the number of years between the first and last use as a means of preventing pregnancy. They also factored in when the women had interruptions of the intake of contraception such as when they had live births.

However, researchers found a minimal risk of endometrial and ovarian cancer due to oral contraceptive use.

“Long-term oral contraceptive use was associated with substantially lower odds of ovarian and endometrial cancers, with women who had been using oral contraceptive for at least 20 years,” the researchers said.

“In contrast, no significant trend with duration of use was observed for breast cancer,” they added.

In the study, about 6.9 per cent of the women were diagnosed with breast cancer. On the other hand, one per cent and 0.8 per cent were found to have endometrial and ovarian cancers, respectively.

Drug development

“The number of cases is significantly higher among never oral contraceptive users, as compared to ever users,” the researchers said.

The researchers examined occurrence in the active years of using oral contraceptives for endometrial cancer. “The lower incidence rate for endometrial cancer among oral contraceptive users appears to be constant during the period of use, which results in very strong cumulative odds of cancer with a long duration of use,” they said.

On the contrary, ovarian cancer had different results compared to endometrial cancer.

“Ovarian cancer appears to be more pronounced in the beginning of the use, and extrapolating from the data, one could speculate that after 30 years of oral contraceptive use, one more year does not add more protection against ovarian cancer,” they explained.

In terms of age, the older women were more likely to become at risk of getting the cancers. For instance, one is likely to get endometrial cancer between the age of 45 and 60. Ovarian will occur at a higher age.

Since the analysis was conducted in older women who started using contraceptives more than 50 years ago, so much has changed on the use of oral contraceptives including the age at which women start using them.

 “Today, most oral contraceptive users take  lower doses of oestrogen and other types of progesterone, as compared to formulas in the preparations commonly used in the 1960s and 70s, when many of the participants in the study started using oral contraceptives,” the researchers said.

“Our results may therefore not directly be applicable to the oral contraceptives that are commonly used today, but should be important for future drug development of cancer prevention and of new types of contraceptives,” they advised.


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