Cervical Cancer

British Columbia Specific Information

Cervical cancer is a disease in which the cells of the cervix become abnormal and start to grow uncontrollably, forming tumors. A Pap test, also known as a Papanicolaou test or pap smear, is a test used to determine if there are abnormal cells in the cervix. If abnormal cells are found, steps can be taken to try to prevent them from developing into cervical cancer. In Canada, a Pap test is the most effective and recommended screening test for cervical cancer. In B.C., it is recommended women aged 25-69 be screened every 3 years. To learn more about the cervical cancer screening program in B.C., including guidelines on who should be tested, visit BC Cancer Agency - Cervix Screening.

Approximately 70 per cent of all cervical cancer is caused by the human papillomavirus (HPV) types 16 and 18. The HPV vaccines, Cervarix^® (HPV2) and Gardasil^® (HPV4), protect against infection from certain types of human papillomaviruses (HPV). Health Canada approves the HPV vaccine Gardasil^® (HPV4) for use in women and men. Health Canada also approves the HPV vaccine Cervarix^® (HPV2) for use in women; however it is not currently approved for use in men.

Some groups are eligible to receive the vaccine for free. Those not eligible to receive the vaccine for free may purchase it from a pharmacy or doctor’s office. For information about the vaccine, including who is eligible to receive it for free, see HealthLinkBC File #101b Human Papillomavirus (HPV) Vaccine.

For more information about HPV see HealthLinkBC File #101a Human Papillomavirus (HPV) Infection and Genital Warts. For information on other HPV vaccine programs in B.C., visit ImmunizeBC - HPV (Human Papillomavirus).

Topic Overview

Is this topic for you?

This topic talks about the testing, diagnosis, and treatment of cervical cancer. For general information about abnormal Pap test results, see the topic Abnormal Pap Test.

What is cervical cancer?

Cervical cancer occurs when abnormal cells on the cervix grow out of control. The cervix is the lower part of the uterus that opens into the vagina. Cervical cancer can often be successfully treated when it's found early. It is usually found at a very early stage through a screening test, such as the Pap test.

What causes cervical cancer?

Most cervical cancer is caused by a virus called human papillomavirus, or HPV. You can get HPV by having sexual contact with someone who has it. There are many types of the HPV virus. Not all types of HPV cause cervical cancer. Some of them cause genital warts, but other types may not cause any symptoms.

Most adults have been infected with HPV at some time. An infection may go away on its own. But sometimes it can cause genital warts or lead to cervical cancer. That's why it's important for women to have regular cervical cancer screening tests. A Pap test can find changes in cervical cells before they turn into cancer. If you treat these cell changes, you may prevent cervical cancer.

What are the symptoms?

Abnormal cervical cell changes rarely cause symptoms. But you may have symptoms if those cell changes grow into cervical cancer. Symptoms of cervical cancer may include:

Bleeding from the vagina that is not normal, such as bleeding between menstrual periods, after sex, or after menopause.
Pain in the lower belly or pelvis.
Pain during sex.
Vaginal discharge that isn't normal.

How is cervical cancer diagnosed?

As part of a pelvic examination, you may have a Pap test. During a Pap test, the doctor scrapes a small sample of cells from the surface of the cervix to look for cell changes. If a Pap test shows abnormal cell changes, your doctor may do other tests to look for precancerous or cancer cells on your cervix.

Your doctor may also do a Pap test and take a sample of tissue (biopsy) if you have symptoms of cervical cancer, such as bleeding after sex.

How is it treated?

The treatment for most stages of cervical cancer includes:

Surgery, such as a hysterectomy and removal of pelvic lymph nodes with or without removal of both ovaries and fallopian tubes.
Chemotherapy.
Radiation therapy.

Depending on how much the cancer has grown, you may have one or more treatments. And you may have a combination of treatments. If you have a hysterectomy, you won't be able to have children. But a hysterectomy isn't always needed, especially when cancer is found very early.

Finding out that you have cancer can change your life. You may feel like your world has turned upside down and you have lost all control. Talking with family, friends, or a counsellor can really help. Ask your doctor about support groups. Or call the Canadian Cancer Society (1-888-939-3333) or visit its website at www.cancer.ca.

Can cervical cancer be prevented?

The Pap test can find cervical cell changes that can lead to cervical cancer. Regular Pap tests almost always show these cell changes before they turn into cancer. It's important to follow up with your doctor after any abnormal Pap test result so you can treat abnormal cell changes. This may help prevent cervical cancer.

There are two HPV vaccines in BC. Cervarix® is approved for females ages 9 through 45 years. It protects against two types of HPV that cause most cases of cervical cancer. Gardasil®9 is approved for use in females 9 through 45 years of age, but is also approved for use in males 9 to 26.

HPV vaccine recommendations may be different in your province or territory. Check with your doctor or provincial ministry of health to find the HPV vaccine recommendations in your area.

The virus that causes cervical cancer is spread through sexual contact. The best way to avoid getting a sexually transmitted infection is to not have sex. If you do have sex, practice safer sex, such as using condoms and limiting the number of sex partners you have.

Health Tools

Health Tools help you make wise health decisions or take action to improve your health.

Decision Points focus on key medical care decisions that are important to many health problems.

Actionsets are designed to help people take an active role in managing a health condition.

Cause

Cervical cancer is caused by severe abnormal changes in the cells of the cervix. Most precancerous or cancerous cell changes occur in the cervix at the transformation zone, because these cells normally undergo constant change. During this natural process of change, some cervical cells can become abnormal if you are infected with high-risk types of HPV.

Other things may play a role in causing cervical cancer, such as having more than one sex partner or smoking cigarettes.

Symptoms

Abnormal cervical cell changes rarely cause symptoms. If cervical cell changes progress to cancer, symptoms may include:

Vaginal bleeding that isn't normal, such as between menstrual periods, after sex, or after menopause.
Pain during sex.
Vaginal discharge that isn't normal.
A significant unexplained change in your menstrual cycle.

The symptoms of advanced cervical cancer may include:

Anemia because of abnormal vaginal bleeding.
Ongoing pelvic, leg, or back pain.
Urinary problems because of blockage of a kidney or ureter.
Leakage of urine or stool into the vagina. This can happen when an abnormal opening (fistula) has developed between the vagina and the bladder or rectum.
Weight loss.

What Happens

Cervical cancer happens when abnormal cells on the cervix grow out of control. Cervical cancer can often be successfully treated when it's found early. It is usually found at a very early stage through a screening test, such as the Pap test.

If cervical cancer isn't treated, it may spread from the cervix to the vagina, and then into deeper tissue layers of connective tissue around the uterus. As it progresses, it may spread to the pelvic lymph nodes and other pelvic organs. Advanced-stage cancer may spread to lymph nodes; to other organs in the pelvis, causing problems with kidney and bowel function; or to other organs in the body, such as the liver and lungs.

Treatment of cervical cancer depends on the stage of your cancer and if it has spread.

What Increases Your Risk

A risk factor for cervical cancer is something that increases your chance of getting this cancer. Having one or more of these risk factors can make it more likely that you will get cervical cancer. But it doesn't mean that you will definitely get it. And many people who get cervical cancer don't have any of these risk factors.

Things that may increase your risk for cervical cancer include:

Having an ongoing infection with a high-risk type of human papillomavirus (HPV) . HPV is a sexually transmitted infection (STI). It is the most common cause of cervical cancer.
High-risk sexual behaviours. These include having more than one sex partner or having a sex partner who has more than one partner. Safer sex can reduce your risk.
Having an impaired immune system . Some conditions such as HIV can make you more likely to get an HPV infection.
Smoking cigarettes or breathing in second-hand smoke.

When should you call your doctor?

Call your doctor if you have:

Unexpected bleeding between menstrual periods.
Menstrual periods that are irregular or 1½ to 2 times longer than normal for 3 months in a row. For example, call if your periods usually last 6 days but have been lasting between 9 and 12 days for your last 3 periods.
Severe vaginal bleeding that causes you to soak 1 or 2 pads or tampons in 1 or 2 hours, or passing clots of blood from the vagina.
Unexpected bleeding after douching or sex.
Pain during sex.
Abnormal vaginal discharge containing mucus that may be tinged with blood.

If you are diagnosed

If you have been diagnosed with cervical cancer, be sure to follow your doctor's instructions about calling when you have problems, new symptoms, or symptoms that get worse.

Who to see

Health professionals who can evaluate your symptoms and your risk factors, and who can diagnose cervical cancer include:

Family doctors or general practitioners.
Gynecologists.
Obstetricians.
Nurse practitioners.
Internists.

Doctors who can manage your cancer treatment include:

Examinations and Tests

Early detection

Screening tests can help your doctor find and treat cervical cell changes before they progress to cervical cancer.

The recommended screening schedule is based on your age and things that increase your risk. Talk to your doctor about how often to have this test.

Diagnostic tests

Tests to confirm a diagnosis of cervical cancer include:

A colposcopy and cervical biopsy. This test can find out whether and where cancer cells are on the surface of the cervix.
An endocervical biopsy (or curettage). This test is to find out whether cancer cells are in the cervical canal.
A cone biopsy. This type of biopsy may be done to remove cervical tissue for examination under a microscope.

Tests to find out the stage and treatment

Tests to find the extent (stage) of cervical cancer include:

A chest X-ray to check your lungs.
A CT scan, which uses X-rays to look inside the body.
An ultrasound, which uses sound waves to check internal tissues and organs.
An MRI, which uses magnets to see inside the body.
A PET scan to check for cancer that has spread (metastasized) to other parts of the body.
A biopsy using fine-needle aspiration.

Treatment Overview

Cervical cancer found in its early stages can be successfully treated. The choice of treatment and the long-term outcome (prognosis) of cervical cancer depend on the type and stage of cancer. Your age, overall health, quality of life, and desire to be able to have children must also be considered.

Types of treatment

Treatment choices for cervical cancer may be a single therapy or a combination of therapies, such as:

Surgery to remove the cancer. The type of surgery needed depends on the location and extent of cervical cancer and whether you want to have children.
Radiation therapy, which uses high-dose X-rays or implants in the vaginal cavity to kill cancer cells. It is used for certain stages of cervical cancer. It is often used in combination with surgery. To learn more, see Other Treatment.
Chemoradiation, which is a combination of chemotherapy and radiation. This is often used to treat both early-stage and late-stage cervical cancer.
Chemotherapy, which uses medicines to kill cancer cells. Chemotherapy may be used to treat advanced cervical cancer.

You can find more information about cervical cancer online at the:

Canadian Cancer Society website at www.cancer.ca.
U.S. National Cancer Institute website at www.cancer.gov.

Coping with emotions during treatment

When you first find out that you have cancer, you may feel scared or angry. Or you may feel very calm. It's normal to have a wide range of feelings and for those feelings to change quickly. Some people find that it helps to talk about their feelings with family and friends.

If your emotional reactions to cancer get in the way of your ability to make decisions about your health, it's important to talk with your doctor. Your cancer treatment centre may offer psychological services. And a local chapter of the Canadian Cancer Society can help you find a support group.

Body image and sexual problems

Your feelings about your body and your sexuality may change following treatment for cancer. Managing body image issues may involve talking openly with your partner about your feelings and discussing your concerns with your doctor. Your doctor may be able to refer you to organizations that can offer additional support and information.

Treatment during pregnancy

Cancer treatment during pregnancy is the same as for non-pregnant women. But when you'll get treatment may depend on the stage of your cancer and what trimester you are in. For example, if you have early-stage cervical cancer and you are in your third trimester, your treatment may be delayed until after you deliver your baby. Treatment may cause problems such as an early delivery or even the loss of the baby.

Follow-up care

After treatment for cervical cancer, it is important to receive follow-up care. Your oncologist or gynecologic oncologist will schedule regular checkups that will include:^{footnote 1}

A pelvic examination and Pap test every 3 to 4 months for the first 2 years.
After the first 2 years, a pelvic examination and Pap test every 6 to 12 months for another 3 to 5 years.
After 5 years, a pelvic examination and Pap test every year.

Follow-up tests that may be recommended by your oncologist include an abdominal and pelvic computed tomography (CT) scan. This test is to see if cancer has spread to other organs in the belly or pelvis.

Cervical cancer that comes back

Cervical cancer can return, or recur, after treatment. The chance that your cancer will return depends on the stage of the initial cancer. Cancer found early is less likely to come back than cancer found at a later stage.

Your long-term outcome (prognosis) for recurrent cervical cancer depends greatly on how much the cancer has spread when the recurrence is diagnosed.

Treatments include surgery and chemoradiation or chemotherapy to relieve symptoms. Your doctor may talk with you about being in a clinical trial. Clinical trials for cervical cancer are studying therapies that target cancer cells.

Hospice palliative care

Cancer treatment has two main goals: curing cancer and making your quality of life as good as possible. Hospice palliative care can improve your quality of life by helping you manage your symptoms. It can also help you with other concerns that you may have when you are living with a serious illness.

For some people who have advanced cancer, a time comes when treatment to cure cancer no longer seems like a good choice. This can be because the side effects, time, and emotional stress of treatment are greater than the promise of cure or relief. But this isn't the end of treatment. Hospice palliative care providers will work to help manage pain and other symptoms or side effects. They may help you decide what treatment you want or don't want. And they can help your loved ones understand how to support you.

It can be hard to decide when to stop treatment aimed at prolonging your life and shift the focus to end-of-life care. You and your doctor can decide when you may be ready for hospice palliative care.

To learn about supportive care, see:

Prevention

You can treat early cervical cell changes (dysplasia), which can reduce your risk for cervical cancer. You can also reduce your risk for abnormal cell changes.

Have regular Pap test screening

The recommended Pap test schedule is based on your age and things that increase your risk. Talk to your doctor about how often to have this test.

Quit smoking

Women who smoke cigarettes or who breathe in second-hand smoke have a higher risk for cervical cell changes that can lead to cervical cancer.^{footnote 2} Quitting smoking may decrease this risk.

For information about quitting, see the topic Quitting Smoking.

Get the HPV vaccine

If you are a woman age 45 or younger, you may be able to get a HPV vaccine. HPV vaccines protect against HPV. There are many types of HPV. Some types of the virus can cause cervical cancer. HPV vaccines protect against the most common HPV types that can cause serious problems. For more information, see the topic Immunizations.

HPV vaccine recommendations may be different in your province or territory. Check with your doctor or provincial ministry of health to find the HPV vaccine recommendations in your area.

HPV: Should My Child Get the Vaccine?
HPV: Should I Get the Vaccine?

Reduce your risk of a sexually transmitted infection (STI)

Preventing an STI, including HPV, is easier than treating an infection after it occurs. HPV infection usually doesn't cause symptoms, so you or your partner may not know that you are infected.

To reduce your risk:

Talk with your partner about STIs before beginning a sexual relationship. Find out if he or she is at risk for an STI. Remember that it's possible to be infected with an STI without knowing it. Some STIs, such as HIV, can take up to 6 months before they are detected in the blood.
Be responsible.
- Avoid sexual contact if you have symptoms of an STI or are being treated for an STI.
- Avoid all intimate sexual contact with anyone who has symptoms of an STI or who may have been exposed to an STI.
The fewer sex partners you have in your lifetime, the better it is for your health. Your risk for an STI increases if you have several sex partners or if your sex partner has more than one partner.
Use male or female condoms to reduce the risk of getting an STI. Using male condoms when you have sex has been shown to reduce your risk of getting HPV.^{footnote 3} Female condoms may help also, although there has been less study of this type of protection.

Not having sexual contact is the only certain way to prevent exposure to STIs. Sexually transmitted infections such as human papillomavirus (HPV) can be spread to or from the genitals, anus, mouth, or throat during sexual activities.

Home Treatment

The side effects of cancer treatment can be serious. Healthy habits such as eating a balanced diet and getting enough sleep and exercise may help control your symptoms. Your doctor may also give you medicines to help you with certain side effects.

Home treatment for nausea or vomiting includes watching for and treating early signs of dehydration. Signs include a dry mouth, sticky saliva, and reduced urine output with dark yellow urine. Eating smaller meals may help. A little bit of ginger candy or ginger tea can help too.
Home treatment for diarrhea includes resting your stomach and being alert for signs of dehydration. Check with your doctor before using any non-prescription medicines for your diarrhea.
Home treatment for constipation includes making sure that you drink enough fluids and include fruits, vegetables, and fibre in your diet each day. Don't use a laxative without consulting your doctor.

Other symptoms that can be treated at home include:

Sleep problems. If you find that you have trouble sleeping, learn ways to manage sleep problems, such as having a sleep routine and making sure your bedroom is dark and quiet.
Fatigue. If you don't have any energy and tire easily, try some tips to help your fatigue. These include getting extra rest, eating a balanced diet, and reducing your stress.
Urinary problems, which can be caused by both cervical cancer and its treatment. It may help to remove caffeinated drinks from your diet and to establish a schedule of urinating every 3 to 4 hours, whether you feel the need or not.
Hair loss . Hair loss may be unavoidable. But using mild shampoos and avoiding damaging hair products will reduce irritation of your scalp.
Stress. Managing stress may include expressing your feelings to others. Learning relaxation techniques may also be helpful. Relaxation techniques, such as meditation, and support groups may help too.
Pain. Not all forms of cancer treatment cause pain. But if you do have pain, there are many home treatments that can help.

Cancer: Controlling Cancer Pain.

Problems after hysterectomy may include:

Pelvic weakness. Kegel exercises can help strengthen the pelvic muscles.
Vaginal dryness. Lubricants, such as Astroglide or K-Y Jelly, may help. Or talk to your doctor about a low-dose vaginal estrogen cream, ring, or tablet.
Pain during sexual intercourse if your vagina was shortened during surgery. Changing positions may help make sex less painful. Talk with your doctor if you have any problems during sex that you think may be related to your surgery.

Having cancer can change your life in many ways. For support in managing these changes, see the topic: Getting Support When You Have Cancer.

Medications

Chemotherapy is used to shrink cervical cancer and decrease tumour growth. It may be used alone or along with radiation (chemoradiation).

Chemoradiation, compared with radiation alone, improves survival in early-stage cervical cancer.^{footnote 4} Chemoradiation can be used as the main treatment or after a hysterectomy.

Chemotherapy may be used to treat cervical cancer that has spread beyond the cervix.

Medicine choices

Chemotherapy medicines used to treat cervical cancer may include carboplatin, cisplatin, and paclitaxel.

Dealing with side effects of medicines

Most chemotherapy will cause some side effects, such as nausea, vomiting, and hair loss. Your doctor may also give you medicines to control and prevent nausea and vomiting. Home treatment may also help relieve other common side effects of cancer treatment.

Cancer: Controlling Nausea and Vomiting From Chemotherapy

Surgery

Surgery to remove the cancer depends on the location and extent of cervical cancer and your desire to be able to have children. You also may be given radiation therapy, chemotherapy, or a combination of the two (chemoradiation). These treatments may be given before or after surgery to try to destroy any cancer cells that may remain or to help control or shrink the tumour.

Surgery choices

Surgery for very early stages of cervical cancer may preserve your ability to have children. Surgeries include:

Cone biopsy (conization) . This removes a wedge of cervical tissue that contains the cancer.
Radical trachelectomy . This removes the cervix, part of the vagina, and the pelvic lymph nodes (lymph node dissection). But the uterus is left in place.

Surgery for most stages of cervical cancer does not preserve your ability to have children. Surgeries include:

Hysterectomy . This is surgery to remove the uterus and cervix . During this surgery, the ovaries and fallopian tubes may also be removed to reduce the chances of recurrence.
Pelvic exenteration (say "ig-ZEN-tuh-ray-shun"). This is the most serious pelvic surgery. It is done when cancer has spread throughout the lower belly and pelvis. In this surgery, the uterus, cervix, vagina, ovaries, fallopian tubes and lymph nodes are removed. The rectum, bladder, or both may also be removed. Artificial openings are made so urine and stool can pass from the body into a collection bag. An artificial vagina can also be created during this surgery.

Dealing with side effects of surgery

Side effects from a conization usually include mild cramping, soreness, spotting and bleeding, and dark-brown or yellow vaginal discharge. These symptoms can happen during the first few hours to the first few weeks. This surgery may be done in your doctor's office, at a colposcopy clinic or at a hospital.

A hysterectomy is major surgery with general anesthesia, so you will likely be in the hospital for a few days. As soon as you feel strong enough, get up and move around as much as you can. This helps prevent problems after surgery like blood clots, pneumonia, and gas pains.

Other side effects from hysterectomy may include:

Pain or discomfort for a few days. Medicines can help with this, so talk with your doctor about pain medicines before your surgery.
Short-term effects, such as feeling sick to your stomach or having trouble emptying your bladder. These problems usually go away on their own after a few hours.
Early menopause, if you have not yet started menopause. You won't have menstrual periods any more. You may have hot flashes, vaginal dryness, night sweats, or other symptoms of menopause. Before your surgery, talk with your doctor about hormone therapy and other treatment options.
Changes in sexual response. For some women, having a hysterectomy changes their sexual response. If you notice any sexual problems, talk with your doctor.

For more information, see the topic Sexual Problems in Women.

Other Treatment

Radiation therapy

Radiation therapy is used for certain stages of cervical cancer, often along with surgery. Chemotherapy may be given at the same time as radiation treatment (chemoradiation) to improve survival rates. Chemoradiation may be used as the main treatment or after a hysterectomy.

Radiation therapy uses high-energy X-rays to kill cancer cells and shrink tumours. Radiation may come from a machine outside the body (external beam radiation therapy). Or it may come from radiation material (radioisotopes) in thin plastic tubes inserted through the vagina into the cervical area where the cancer cells are found (brachytherapy).

Dealing with side effects of radiation

Radiation may cause many side effects, including diarrhea and irritation of the bladder (radiation cystitis). Home treatment may help relieve some common side effects of cancer treatment.

Your ability to have or enjoy sexual intercourse may also be affected. This is because radiation may cause changes to the cells lining the vagina (mucosa), making intercourse difficult or painful. A series of vaginal dilators, starting with a small one and progressing to a larger size, may be used after radiation therapy. Using the dilators can help by making the vaginal opening larger.

Radiation to treat cervical cancer may thin the bone and increase the risk of fractures in the pelvic area, including hip fractures. You can take steps to prevent thinning of the bone (osteoporosis), such as getting enough calcium and vitamin D. Also, try to prevent falls, which can lead to fractures. For more information, see the topic Osteoporosis.

Clinical trials

Some women who have cervical cancer may be interested in taking part in research studies called clinical trials. Clinical trials are designed to find better ways to treat cancer patients. They are based on the most up-to-date information. Women who don't want standard treatments or are not cured using standard treatments may want to take part in clinical trials. These are ongoing in many Canadian provinces and in some other countries for all stages of cervical cancer.

Complementary therapy

People sometimes use complementary therapies along with medical treatment to help relieve symptoms and side effects of cancer treatments. Some of the therapies that may be helpful include:

Acupuncture. It can relieve pain and may help you deal with nausea and vomiting from chemotherapy.
Meditation or yoga. These mind-body treatments relieve stress. They may help you feel better and cope with treatment.
Light massage (not deep tissue or intense pressure) or biofeedback. These can ease tension.
Breathing exercises or aromatherapy. They can help you relax and feel less anxious.

These mind-body treatments may help you feel better. They can make it easier to cope with treatment. They also may reduce chronic low back pain, joint pain, headaches, and pain from treatments.

Before you try a complementary therapy, talk to your doctor about the possible value and potential side effects. Let your doctor know if you are already using any of these therapies. They are not meant to take the place of standard medical treatment.

References

Citations

National Comprehensive Cancer Network (2012). Cervical Cancer, version 1. Available online: http://www.nccn.org/professionals/physician_gls/PDF/cervical.pdf.

National Cancer Institute (2012). Cervical Cancer (PDQ): Prevention—Health Professional Version. Available online: http://www.cancer.gov/cancertopics/pdq/prevention/cervical/HealthProfessional.

Winer RL, et al. (2006). Condom use and the risk of genital human papillomavirus infection in young women. New England Journal of Medicine, 354(25): 2645–2654.

Martin-Hirsch PL, Wood NJ (2011). Cervical cancer, search date October 2009. BMJ Clinical Evidence. Available online: http://www.clinicalevidence.com.

Other Works Consulted

American Cancer Society (2011). Cancer Facts and Figures for African Americans 2011–2012. Atlanta. American Cancer Society. Available online: http://www.cancer.org/acs/groups/content/@epidemiologysurveilance/documents/document/acspc-027765.pdf.

National Cancer Institute (2011). Cervical Cancer PDQ: Treatment—Patient Version. Available online: http://www.cancer.gov/cancertopics/pdq/treatment/cervical/patient.

National Cancer Institute (2012). Cervical Cancer PDQ: Treatment—Health Professional Version. Available online: http://www.cancer.gov/cancertopics/pdq/treatment/cervical/HealthProfessional.

U.S. Preventive Services Task Force (2012). Screening for cervical cancer: Summary of recommendations. Available online: http://www.uspreventiveservicestaskforce.org/uspstf/uspscerv.htm.