Cervical cancer risk factors: HPV, smoking and what helps

What cervical cancer is

The cervix is the lower, narrow end of the uterus (womb), which opens into the vagina. Cervical cancer usually develops slowly. Before the cells become cancer, they start to look abnormal; these cells are called precancers. If they are not destroyed or removed, they may become cancer (MedlinePlus). Cervical cancer is most common in people over age 30 (MedlinePlus).

The main cause: a long-lasting HPV infection

A long-lasting (persistent) infection with high-risk types of human papillomavirus (HPV) causes virtually all cervical cancers. Two high-risk types, HPV 16 and HPV 18, cause 70% of cervical cancers worldwide (NCI).

Nearly all people who are sexually active will get HPV at some point in their lives. Most infections go away on their own within a year or two as the immune system controls them, and these short-term infections do not cause cancer. When a high-risk infection lasts for years, it can change the cells of the cervix into a precancer, which may in time become cancer if it is not found and removed (NCI). HPV passes through close skin-to-skin touching, usually during vaginal, anal or oral sex, and most people who have it have no symptoms (MedlinePlus).

People who become sexually active at a young age, especially before age 18, or who have multiple sexual partners are more likely to get a high-risk type of HPV (NCI).

What makes an HPV infection more likely to turn into cancer

For someone who has a high-risk HPV infection of the cervix, the NCI and MedlinePlus list these (NCI) (MedlinePlus):

• A weakened immune system. For example HIV or another disease that weakens the immune system, or medicine that holds the immune system back, such as after an organ transplant, or to treat an autoimmune disease or cancer. HPV infections are more likely to last and to progress to cancer in these people (NCI).
• Smoking or secondhand smoke. The risk goes up the more a person smokes or is exposed to secondhand smoke (NCI).
• Birth control pills and many births. Both are linked to a higher risk. The reasons are not well understood (NCI).
• Obesity. Screening may be harder in people with obesity, so precancers are found less often and the cancer risk is higher (NCI).

DES exposure before birth is a rare cause. Between 1940 and 1971, a drug called diethylstilbestrol (DES) was given to some pregnant women in the United States. People whose mothers took it while pregnant have a higher risk of abnormal cervical cells and of a type of cancer called clear cell adenocarcinoma of the vagina and cervix (NCI) (MedlinePlus).

Which ones you can change

How most cervical cancers are prevented

The NCI says cervical cancer is highly preventable and highly curable if caught early. Nearly all cervical cancers could be prevented by HPV vaccination, routine screening, and follow-up treatment when needed (NCI).

• The HPV vaccine. Gardasil 9 is approved in the United States for females and males aged 9 to 45. It works best before a person becomes sexually active, and it does not treat an infection you already have. The CDC recommends it at age 11 or 12, and it can start at 9. Anyone not vaccinated by then is advised to get it up to age 26; some adults from 27 to 45 may choose it after talking with their doctor (NCI). The HPV vaccine age check shows where you stand and how many doses apply.
• Screening. HPV tests and Pap tests can find high-risk HPV and abnormal cells and precancers that can be treated before they turn into cancer. Because the vaccine does not protect against every cancer-causing HPV type, regular screening is still important (NCI).
• Follow-up. Getting the right follow-up treatment if a test finds abnormal cells or high-risk HPV (MedlinePlus).
• Condoms. They lower the chance of passing HPV but do not prevent it completely, because HPV can be on skin the condom does not cover (NCI).

Symptoms to report

Cervical cancer usually does not cause symptoms when it first starts to grow. When it does, MedlinePlus lists (MedlinePlus):

• Vaginal bleeding that is not normal for you, such as bleeding after sex or between periods
• Watery vaginal discharge with a strong odor or that contains blood
• Pelvic pain or pain during sex

Because early cervical cancer often has no symptoms, screening matters even when you feel well. If you notice any of these, see your provider rather than waiting for your next screening.

What the USPSTF says about screening by age

The US Preventive Services Task Force 2018 recommendation applies to people with a cervix at average risk and with no symptoms (USPSTF 2018):

It does not apply to people with a high-grade precancer or cervical cancer, people exposed to DES before birth, or people with a weakened immune system, such as those living with HIV (USPSTF 2018). They need a schedule set with their doctor. The cervical cancer screening age check compares this with the American Cancer Society guideline and the USPSTF draft update, and screening tests by age lists the other checks for your age.

Common questions

Does having HPV mean I will get cervical cancer?

No. Most HPV infections go away on their own within a year or two and do not cause cancer. The risk comes from high-risk types that last for years (NCI). Screening finds those changes early.

I had the HPV vaccine. Do I still need screening?

Yes. The vaccine does not protect against all HPV types that can cause cervical cancer, so regular screening is still important (NCI).

Is it too late for the vaccine if I am already sexually active?

Not always. People who are already sexually active may benefit less, because they may have been exposed to some of the HPV types the vaccine targets (NCI). Vaccination is recommended up to age 26; from 27 to 45 it is a choice to talk through with your doctor (NCI).