“We found long-term use of oral contraceptive pills higher among those suffering from breast cancer-11.9 percent – compared to healthy individuals—1.2 percent,” Dr. Umesh Kapil, a professor at the All India Institute of Medical Sciences’ public health nutrition unit, told the Times of India.
The study, published in the Indian Journal of Cancer, included 640 women, of whom 320 were breast cancer patients. Researchers found a breast cancer risk 950 percent – 9.5 times – higher in women with a history of using oral contraceptives.
Kapil said breast cancer is caused by repeated exposure of breast cells to ovarian hormones. The contraceptive pills’ estrogen and progesterone may increase this risk through hormonal imbalances.
Dr. G. K. Rath, the head of Bhim Rao Ambedkar Institute Rotary Cancer Hospital, said the relationship between contraceptive use and breast cancer occurrence is not known.
“But there is enough evidence to show the hormonal imbalance caused by them, increasing the risk,” Rath said.
The doctor said other important factors in breast cancer occurrence include early menarche, late marriage and childbirth, and abortions.
Dr. Ajeet Singh Bhadoria, a co-author of the study, suggested its findings could also be relevant to the use of morning-after pills, which contain a higher dose of hormones.
“Awareness about the side-effects of long-term use is a must,” he told the Times of India.
Some contraceptives are classified as carcinogenic by the World Health Organization and their use could increase risk for cervical and liver cancers.
Other studies have indicated that the contraceptive pill increases the risk of deadly blood clots and stroke.