CAN TAKING ORAL CONTRACEPTIVES CAUSE CANCER?
Brenda is a 25 year old newly-wed, who wants to postpone having a family while she and her husband try to earn a living. They have decided that Brenda take oral contraceptive pills to prevent pregnancy. Brenda is quite anxious of a possibility that she may develop breast cancer or any cancer for that matter. She is confused from what she hears from her family, her co-workers, and what she reads on the internet. She asks, “Can taking oral contraceptives cause cancer?”
What are oral contraceptives made of?
Typically oral contraceptives contain two hormones, estrogen and progesterone. These hormones are normally produced by a woman's ovaries. Estrogen is secreted in the first half of a woman's menstrual cycle which thickens the lining of the uterus or womb. Progesterone is secreted in the second half, in which it stabilizes the uterine lining to prepare it for a possible pregnancy. If no pregnancy occurs, progesterone levels decline which results in menstruation. If pregnancy does occur, progesterone secretion continues and this prevents ovulation or release of additional eggs from the ovaries. This is the mechanism in which oral contraceptives (OCs) work. They contain a low dose of man-made estrogen and progesterone which prevents ovulation. Since OC's contain these hormones, there are concerns like taking them can lead to cancer, especially those cancers which are biologically dependent on hormones.
In a nutshell, studies are conflicting. Some studies say that there is a slight increase for developing breast cancer, while some studies say that there is none.
An analysis by the Collaborative Group on Hormonal Factors in Breast Cancer found that 153,536 women worldwide who currently use or recently used OCs, especially if started during the teenage years, had higher chances of developing breast cancer.
But after careful observation, those women who have stopped using OC's 10 or more years after, regardless of breast cancer history, ethnic background and reproductive record, had the same risk level for the disease almost as if they never used birth control pills in the first place.
But in another study conducted by Women's CARE (Women's Contraceptive and Reproductive Experiences), around 50,437 women who took the pill had no alarming significance on the risks for breast cancer.
Since the jury is still out on breast cancer risk, the patient must consult with her physician before starting the pill. Other risk factors for breast cancer, such as older age, family history and diet should be taken into account. Women should ask their doctors about when to begin mammograms and breast exams for breast cancer prevention. In the end, it is about individualized patient care and the informed decision of the patient.
Cervical cancer is strongly associated with oral contraceptives. In 2007, the International Collaboration of Epidemiological Studies of Cervical Cancer showed that the risk increases the longer you take the pill. The same analysis showed that the risk of developing cervical cancer goes down when the OCs were discontinued.
Although OCs may increase the risk for cervical cancer, the major culprit of the disease is the human papillomavirus (HPV). HPV is mainly contracted from sexual contact with a partner who has the virus. Some types of HPV, the high-risk types, are able to incorporate their DNA into the cells of the cervix, transforming them into cancer cells. Thus, increased exposure to the virus by having multiple sexual partners and coitus at a young age, when the cervix is most prone to infection, increases the risk for cervical cancer.
So how do pills increase risk for cervical cancer if it is the virus that causes it? Anatomically, OCs causes cervical eversion, exposing the vulnerable inner portion of the cervix to the virus. On a molecular level, OCs enhances the incorporation of the DNA of the virus into the cells of the cervix. Thus, it appears that OCs merely help the virus, but on its own, does not cause cancer. Smoking also helps the virus by lessening the immunity of cells of the cervix thus making them more susceptible to HPV. Smoking and oral contraceptives both promote HPV infection and together are a bad combination. Studies have shown that when used together, they even increase a patient's risk for heart disease.
This is not to discourage women from taking OCs for fear of cervical cancer. Instead, this is to encourage women who have taken the pill, especially those who are presently on the pill, to regularly visit their gynecologists for pelvic examination and annual Pap smear. The Pap smear is the most effective screening tool for cervical cancer. Screening enables the doctor to catch the disease at a pre-cancerous or early, curable stage. Smokers should quit smoking before starting the pill to lessen risk for cervical cancer, as well as prevention of heart disease. More importantly, the best way to prevent cervical cancer is to be in a monogamous relationship so as not to be infected with HPV.
Numerous studies uniformly agree that OCs prevent ovarian cancer. Ovarian cancer is thought to be caused by incessant ovulation or the uninterrupted monthly release of eggs during the menstrual cycle. Continuous ovulation destroys the surface of the ovaries, which eventually leads to cancer. In a woman's life, ovulation is halted during pregnancy and breastfeeding. By stopping ovulation, pregnancy and breastfeeding protect women from developing ovarian cancer by preventing damage on the ovaries. OCs work in the same way by preventing monthly ovulation. In a study by Hankinson et al., cancer risk is reduced by 40% with 4 years of use, 53% reduction with 8 years of use and 60% reduction with 12 years of use.
A small percentage of ovarian cancer is hereditary. These affected women have mutations in their BRCA-1 and BRCA-2 genes which predispose them to ovarian cancer. Studies have shown that through OC's, the chances for ovarian cancer is reduced in these groups of women.
Ovarian cancer is considered one of the deadliest cancers of women. Unlike cervical cancer, researchers have yet to discover the ideal screening tool for this disease. Because of a lack of screening tool, women are diagnosed at late stages of the disease, thus making them harder to cure. Prevention of ovarian cancer is one of the major benefits of taking pills.
OCs has a protective effect against endometrial cancer (cancer of the uterine lining). Endometrial cancer is typically caused by estrogen that is not opposed or balanced by progesterone. Uninhibited estrogen causes the lining of the uterus to thicken uncontrollably which may lead to endometrial cancer. The patient usually complains of heavy, irregular vaginal bleeding. Patients who are obese, diabetic or have polycystic ovarian syndrome have increased estrogen in their bodies thus causing increased thickening of the endometrium. OCs contain low doses of estrogen and progesterone which maintain the balance between these two hormones, and ensure monthly shedding of the endometrium through menstruation.
Similar to ovarian cancer, the protective effects of oral contraceptives can then take effect through the duration of use. The risk of developing endometrial cancer was decreased by 54% with 4 years' use, 66% with 8 years' use, and 72% with 12 years' use. This protection appears within 10 years of initial use and persists for at least 15 years after discontinuing the OCs. The greatest protection is seen in women who have never been pregnant or women of few pregnancies, who are at risk for developing endometrial cancer. (Emons, Schlesselman)
Decreased risk of endometrial cancer is one of the clear advantages of OC use. Women should also have lifestyle modifications like diet and exercise to address obesity and diabetes. Diabetics should consult their doctors to keep their blood sugars in check. Patients with irregular menses due to polycystic ovarian syndrome are given medications so they menstruate regularly.
The most common risk factor for liver cancer is chronic or long-term infection with Hepatitis B virus. Hepatitis is transmitted from person to person by unprotected sex, sharing contaminated needles in illicit drug-use, childbirth and blood transfusion. Hepatitis infection is predominantly seen in Southeast Asia and Africa. Thus Asians and African women are considered high risk for liver cancer. In contrast, Caucasian women in the United States and Europe are generally considered low risk for liver cancer.
Studies have shown that oral contraceptives are likely to increase the risk of liver cancer for populations that show lower risk of this disease such as with Caucasian women. However, in Asian and African women who are already considered high risk because of the pervasiveness of Hepatitis B infection, OCs have no added risk for developing liver cancer.
In summary, current studies show that there is an increased risk of developing cervical cancer from taking the pill. Liver cancer risk also increases in some populations. On the other hand, the risk for ovarian and endometrial cancer is reduced through OC's. Studies on the risk of developing breast cancer are conflicting.
Therefore, it is important that the patient and her physician thoroughly discuss the risks and benefits of taking oral contraceptives to reach an informed decision. If a woman decides to take pills, she should be informed of her risk for cancer and on the current recommended screening for cancers. The persuasive ads should not be the sole basis for being convinced about OCs: there is nothing to lose with a medical consult.
1. Collaborative Group on Hormonal Factors in Breast Cancer. Breast cancer and hormonal contraceptives: Collaborative reanalysis of individual data on 53,297 women with breast cancer and 100,239 women without breast cancer from 54 epidemiological studies. Lancet 1996; 347:1713-1727.
2. Emons G, Fleckenstein G, Hinney B, Huschman A, Heyl W. Hormonal interactions in endometrial cancer. Endocrine-Related Cancer 2000; 7(4):227-242.
3. Hankinson SE, Colditz GA, Hunter DJ, et al. A quantitative assessment of oral contraceptive use and risk of ovarian cancer. Obstetrics and Gynecology 1992; 80(4):708-714.
4. International Collaboration of Epidemiological Studies of Cervical Cancer. Cervical cancer and hormonal contraceptives: collaborative reanalysis of individual data for 16,573 women with cervical cancer and 35,509 women without cervical cancer from 24 epidemiological studies. Lancet 2007;370:1609-21.
5. Marchbanks PA, McDonald JA, Wilson HG, et al. Oral contraceptives and the risk of breast cancer. New England Journal of Medicine 2002; 346(26):2025-2032.
6. Schlesselman JJ. Net effect of oral contraceptive use on the risk of cancer in women in the United States. Obstet Gynecol 1995; 85:793.
7. Yu MC, Yuan JM. Environmental factors and risk for hepatocellular carcinoma. Gastroenterology 2004; 127 (5 Suppl 1):S72-S78.