Cervical cancer was once one of the most common causes of cancer death for American women. Over the last 30 years, the cervical cancer death rate has gone down by more than 50%. The main reason for this change is the increased use of screening tests. Screening can find changes in the cervix before cancer develops. It can also find cervical cancer early – when it’s small, has not spread, and is easiest to cure. Another way to help prevent cervical cancer in the future is to have children vaccinated against human papilloma virus (HPV), which causes most cases of cervical cancer.
Cancer starts when cells in the body begin to grow out of control. Cells in nearly any part of the body can become cancer, and can spread to other areas of the body. Cervical cancer starts in the cells lining the cervix — the lower part of the uterus (womb). This is sometimes called the uterine cervix. The fetus grows in the body of the uterus (the upper part). The cervix connects the body of the uterus to the vagina (birth canal). The cervix has two different parts and is covered with two different types of cells.
These two cell types meet at a place called the transformation zone. The exact location of the transformation zone changes as you get older and if you give birth. Most cervical cancers begin in the cells in the transformation zone. These cells do not suddenly change into cancer. Instead, the normal cells of the cervix first gradually develop pre-cancerous changes that turn into cancer. Doctors use several terms to describe these pre-cancerous changes, including cervical intraepithelial neoplasia (CIN), squamous intraepithelial lesion (SIL), and dysplasia. These changes can be detected by the Pap test and treated to prevent cancer from developing.
Although cervical cancers start from cells with pre-cancerous changes (pre-cancers), only some of the women with pre-cancers of the cervix will develop cancer. It usually takes several years for cervical pre-cancer to change to cervical cancer, but it also can happen in less than a year. For most women, pre-cancerous cells will go away without any treatment. Still, in some women pre-cancers turn into true (invasive) cancers. Treating all cervical pre-cancers can prevent almost all cervical cancers.
Cervical cancers and cervical pre-cancers are classified by how they look under a microscope. The main types of cervical cancers are squamous cell carcinoma and adenocarcinoma.
Although almost all cervical cancers are either squamous cell carcinomas or adenocarcinomas, other types of cancer also can develop in the cervix. These other types, such as melanoma, sarcoma and lymphoma occur more commonly in other parts of the body.
A risk factor is anything that changes your chance of getting a disease such as cancer. Different cancers have different risk factors. For example, exposing skin to strong sunlight is a risk factor for skin cancer. Smoking is a risk factor for many cancers. But having a risk factor, or even several, does not mean that you will get the disease.
Several risk factors increase your chance of developing cervical cancer. Women without any of these risk factors rarely develop cervical cancer. Although these risk factors increase the odds of developing cervical cancer, many women with these risks do not develop this disease. When a woman develops cervical cancer or pre-cancerous changes, it might not be possible to say that a particular risk factor was the cause.
In thinking about risk factors, it helps to focus on those you can change or avoid (like smoking or human papillomavirus infection), rather than those you cannot (such as your age and family history). However, it is still important to know about risk factors that cannot be changed, because it’s even more important for women who have these factors to get regular Pap tests to detect cervical cancer early.
Infection by the human papillomavirus (HPV) is the most important risk factor for cervical cancer. HPV is a group of more than 150 related viruses. Some of them cause a type of growth called papillomas, which are more commonly known as warts .
Certain types of HPV may cause warts on or around the female and male genital organs and in the anal area. These are called low-risk types of HPV because they are seldom linked to cancer.
Other types of HPV are called high-risk types because they are strongly linked to cancers, including cancer of the cervix, vulva and vagina in women, penile cancer in men, and cancers of the anus, mouth and throat in both men and women.
Infection with HPV is common, and in most people the body can clear the infection by itself. Sometimes, however, the infection does not go away and becomes chronic. Chronic infection, especially when it is caused by certain high-risk HPV types, can eventually cause certain cancers, such as cervical cancer.
Although there is currently no cure for HPV infection, there are ways to treat the warts and abnormal cell growth that HPV causes.
When someone smokes, they and those around them are exposed to many cancer-causing chemicals that affect organs other than the lungs. These harmful substances are absorbed through the lungs and carried in the bloodstream throughout the body.
Women who smoke are about twice as likely as non-smokers to get cervical cancer. Tobacco by-products have been found in the cervical mucus of women who smoke. Researchers believe that these substances damage the DNA of cervix cells and may contribute to the development of cervical cancer. Smoking also makes the immune system less effective in fighting HPV infections.
Human immunodeficiency virus (HIV), the virus that causes AIDS, damages a woman’s immune system and puts them at higher risk for HPV infections.
The immune system is important in destroying cancer cells and slowing their growth and spread. In women with HIV, a cervical pre-cancer might develop into an invasive cancer faster than it normally would.
Another group of women at risk for cervical cancer are those taking drugs to suppress their immune response, such as those being treated for an autoimmune disease (in which the immune system sees the body’s own tissues as foreign and attacks them, as it would a germ) or those who have had an organ transplant .
Chlamydia is a relatively common kind of bacteria that can infect the reproductive system. It is spread by sexual contact. Chlamydia infection can cause pelvic inflammation, leading to infertility.
Some studies have seen a higher risk of cervical cancer in women whose blood tests and cervical mucus showed evidence of past or current chlamydia infection. Women who are infected with chlamydia often have no symptoms. In fact, they may not know that they are infected at all unless they are tested for chlamydia during a pelvic exam.
Women whose diets don’t include enough fruits and vegetables may be at increased risk for cervical cancer.
Overweight women are more likely to develop adenocarcinoma of the cervix.
There is evidence that taking oral contraceptives (OCPs) for a long time increases the risk of cancer of the cervix. Research suggests that the risk of cervical cancer goes up the longer a woman takes OCPs, but the risk goes back down again after the OCPs are stopped, and returns to normal about 10 years after stopping.
Some research suggests that women who had ever used an intrauterine device (IUD) had a lower risk of cervical cancer. The effect on risk was seen even in women who had an IUD for less than a year, and the protective effect remained after the IUDs were removed.
Using an IUD might also lower the risk of endometrial (uterine) cancer. However, IUDs do have some risks. A woman interested in using an IUD should first discuss the possible risks and benefits with her doctor. Also, a woman with multiple sexual partners should use condoms to lower her risk of sexually transmitted illnesses no matter what other form of contraception she uses.
Women who have had 3 or more full-term pregnancies have an increased risk of developing cervical cancer. No one really knows why this is true. Also, studies have pointed to hormonal changes during pregnancy as possibly making women more susceptible to HPV infection or cancer growth. Another thought is that pregnant women might have weaker immune systems, allowing for HPV infection and cancer growth.
Women who were younger than 17 years when they had their first full-term pregnancy are almost 2 times more likely to get cervical cancer later in life than women who waited to get pregnant until they were 25 years or older.
Many low-income women do not have easy access to adequate health care services, including Pap tests. This means they may not get screened or treated for cervical pre-cancers.
DES is a hormonal drug that was given to some women between 1940 and 1971 to prevent miscarriage. Women whose mothers took DES (when pregnant with them) develop clear-cell adenocarcinoma of the vagina or cervix more often than would normally be expected. These types of cancer are extremely rare in women who haven’t been exposed to DES. There is about 1 case of vaginal or cervical clear-cell adenocarcinoma in every 1,000 women whose mothers took DES during pregnancy. This means that about 99.9% of “DES daughters” do not develop these cancers.
DES-related clear cell adenocarcinoma is more common in the vagina than the cervix. The risk appears to be greatest in women whose mothers took the drug during their first 16 weeks of pregnancy. The average age of women diagnosed with DES-related clear-cell adenocarcinoma is 19 years. Since the use of DES during pregnancy was stopped by the FDA in 1971, even the youngest DES daughters are older than 40 − past the age of highest risk. Still, there is no age cut-off when these women are felt to be safe from DES-related cancer. Doctors do not know exactly how long these women will remain at risk.
DES daughters may also be at increased risk of developing squamous cell cancers and pre-cancers of the cervix linked to HPV.
Cervical cancer may run in some families . If your mother or sister had cervical cancer, your chances of developing the disease are higher than if no one in the family had it. Some researchers suspect that some instances of this familial tendency are caused by an inherited condition that makes some women less able to fight off HPV infection than others. In other instances, women in the same family as a patient already diagnosed could be more likely to have one or more of the other non-genetic risk factors previously described in this section.
In recent years, there has been a lot of progress in understanding what happens in cells of the cervix when cancer develops. The development of normal human cells mostly depends on the information contained in the cells’ DNA. DNA is the chemical in our cells that makes up our genes, which control how our cells work. We look like our parents because they are the source of our DNA. But DNA affects more than just how we look.
Some genes control when cells grow, divide, and die:·
Cancers can be caused by DNA mutations (gene defects) that turn on oncogenes or turn off tumor suppressor genes.
HPV cause the production of two proteins known as E6 and E7 which turn off some tumor suppressor genes. This may allow the cervical lining cells to grow too much and to develop changes in additional genes, which in some cases will lead to cancer.
But HPV is not the only cause of cervical cancer. Most women with HPV don’t get cervical cancer, and certain other risk factors, like smoking and HIV infection, influence which women exposed to HPV are more likely to develop cervical cancer.
The most common form of cervical cancer starts with pre-cancerous changes and there are ways to stop this disease from developing. The first way is to find and treat pre-cancers before they become true cancers, and the second is to prevent the pre-cancers.
A well-proven way to prevent cervical cancer is to have testing (screening) to find pre-cancers before they can turn into invasive cancer. The Pap test (or Pap smear) and the HPV test are used for this. If a pre-cancer is found it can be treated, stopping cervical cancer before it really starts. Most invasive cervical cancers are found in women who have not had regular Pap tests.
The Pap test is a procedure used to collect cells from the cervix so that they can be looked at under a microscope to find cancer and pre-cancer. These cells can also be used for HPV testing. A Pap test can be done during a pelvic exam, but not all pelvic exams include a Pap test.
An HPV test can be done on the same sample of cells collected from the Pap test.
For more information visit the American College of Obstetricians and Gynecologists website.