cervical cancer
- Key People:
- Ian Frazer
- Elizabeth Stern
- Harald zur Hausen
- Related Topics:
- cancer
- human papillomavirus
- cervix
- Gardasil
- Cervarix
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cervical cancer, disease characterized by the abnormal growth of cells in the cervix, the region of the uterus that joins the vagina. Cervical cancer was once a common cause of cancer deaths in women, but fatalities have been greatly reduced since the development of the Pap smear in the 1940s. Cervical cancer is still fairly common; in some developing countries it occurs more often than breast cancer and is the most common form of cancer among women in those countries.
Causes and symptoms
The causes of cervical cancer vary, but most cases are caused by complications associated with human papillomavirus (HPV) infection, a sexually transmitted disease that inhibits the ability of cervical cells to suppress tumours. Other risk factors include smoking, low socioeconomic status, and infection with the human immunodeficiency virus (HIV), the virus that causes AIDS.
The Pap test diagnoses most cervical cancers at an early, noninvasive stage. Gone undetected, however, the cancer may eventually cause vaginal bleeding or other discharge, pelvic pain, or pain during intercourse.
Diagnosis and prognosis
Initial diagnosis often begins with a positive Pap test, which is followed by a more comprehensive examination to confirm the presence of cervical cancer. Examination typically involves colposcopy, in which the epithelial tissues of the cervix, vagina, and vulva are viewed with a lighted magnifying instrument known as a colposcope. A biopsy is then performed either by cone biopsy, in which a cone-shaped region of cells is removed, or by colposcopic biopsy, in which cells are scraped from the lining during a colposcopy procedure. If the cancer is at an advanced stage and metastasis (spreading of the cancer) is suspected, other cancers of the uterus and surrounding tissues can be detected by observing the reproductive, digestive, and urinary tracts with other specialized viewing scopes.
Once cervical cancer has been diagnosed, its stage is then determined. The stage is an indicator of how far the cancer has progressed. Stage 0 cervical cancer is also called carcinoma in situ and is confined to the epithelial cells that line the cervix. Stage I cancers have spread into the connective tissue that underlies the epithelium, whereas stage II cancers have spread beyond the cervix to the upper portion of the vagina or to nearby tissues within the pelvic area. Stage III cancers have spread to the lower portion of the vagina or to the wall of the pelvis. Stage IV cancers have spread to distant organs such as the lungs, bladder, or bone.
The five-year survival rate for cervical cancer is quite high when the cancer is diagnosed in its early, preinvasive state. Many cervical cancers are detected at this point, and nearly all of these patients can be completely cured. Even invasive cancers, when detected early, have a very high five-year survival rate. Once the cancer has spread outside the uterus, however, survival rates are considerably lower.
Treatment
Surgery is an effective treatment for most cervical cancers. Usually, noninvasive cancers can be easily removed with a scalpel or laser during outpatient surgery. Another option is to destroy the cancer by freezing it. If the cancer has spread locally within the tissue, one of two types of hysterectomy may be required. A simple hysterectomy that removes the uterus and cervix will suffice in some cases, whereas in others a radical hysterectomy is necessary to remove the underlying connective tissue (parametrium) and ligaments along with the upper portion of the vagina. If warranted, either of these surgeries may be done in conjunction with removal of the fallopian tubes and ovaries. Surgical removal of the uterus or ovaries results in infertility, and removal of the ovaries causes women immediately to go into menopause. Lymph nodes may also be removed during surgery.
Radiation therapy may also be used in the treatment of cervical cancer, often in conjunction with surgery if the cancer is invasive and has spread beyond the surface of the cervix. External beam radiation resembles traditional X-rays in that the radiation is directed from outside the body toward an internal target tissue. Brachytherapy, on the other hand, uses implanted radioactive rods or pellets to focus the radiation on the cancer and greatly reduce side effects. In addition to the side effects normally associated with radiation treatment, pelvic radiation therapy may also cause premature menopause, bladder irritation, or a narrowing of the vagina due to scar tissue buildup.
Chemotherapy is generally used when cervical cancer has spread beyond the uterus. Once a cancer has spread, general or systemic approaches such as chemotherapy are required to seek out and destroy as many cancerous cells as possible.
Prevention
Most cervical cancers can be prevented by avoiding risk factors and by getting regular Pap tests. The major risk factor for cervical cancer is human papillomavirus infection, which can be reduced or prevented by avoiding sexual contact with individuals who have had multiple sexual partners. In 2006 a vaccine effective against four different types of HPV, including the two strains known to cause most cases of cervical cancer, was approved for use in females between ages 9 and 26. The vaccine is effective only in people who have had no previous infection with HPV. In the decade following the implementation of HPV vaccination, cervical cancer rates dropped significantly, raising hopes that the disease might someday be eliminated (defined as fewer than 4 cases per 100,000 individuals). Condoms are not highly effective at preventing HPV infection. Visible genital warts should be treated immediately to reduce their likelihood of developing into cervical cancer.
Some medical societies recommend that women have their first Pap test plus pelvic exam at age 21, with biennial Pap tests thereafter. At the advice of a physician, the frequency of Pap tests may be reduced if multiple tests prove negative.
The Editors of Encyclopaedia Britannica