Pap Test Accuracy : Risk Factors, Early Detection

by Food and Drug Administration (FDA)

(Page 2 of 2)

Risk Factors

Evidence collected over the past few decades suggests several risk factors for developing cervical cancer. These include having sexual intercourse before age 18, having several sexual partners, or having a sexual partner who previously had a long-term sexual relationship with a woman who had cervical cancer.

Scientists are closely scrutinizing the sexually transmitted human papillomaviruses (HPVs), some of which cause genital warts. Research strongly suggests some types of HPVs (there are more than 60 different types) can trigger the growth of abnormal cells in the cervix and are likely to play a key role in the development of cervical cancer. Women who have HPV or whose partners have HPV have an increased risk of developing cervical cancer.

However, many women infected with HPV do not develop cervical cancer, and not all women with cervical cancer harbor HPV. This suggests other factors act with HPV to cause cervical cancer. The genital herpes virus may play a role, as may the strength of a woman's immune system. Women infected with HIV, the virus that causes AIDS, are more likely to develop cervical cancer, as are female organ transplant patients who receive drugs that suppress the immune system to prevent rejection of the new organ.

Hormones may also influence the development of cervical cancer. The labeling of oral contraceptives states that some studies have found an increased incidence of cervical cancer in women taking birth control pills, but that this may be related to factors other than the pill. Women whose mothers took the estrogen-like drug diethylstilbestrol (DES) during pregnancy to prevent miscarriage are also more likely to develop cervical cancer. (DES was used to prevent miscarriages from about 1940 to 1970.)

Smoking also elevates the risk of cervical cancer, which rises with the number of cigarettes a woman smokes each day and with the number of years she has smoked. Women exposed to other people's tobacco smoke are also more likely to develop cervical cancer.

Research suggests women can reduce their risk of cervical cancer by using barrier methods of contraception, such as the diaphragm with spermicide and condoms, probably because such methods decrease the risk of being infected by a sexually transmitted disease.

At present, early detection of precancerous tissue remains the most effective way of preventing cervical cancer. When detected in its early stages nearly all cervical cancers can be cured with minor surgery or other practices.

In contrast, fewer than 20 percent of women with advanced cervical cancer survive more than five years, even with treatment, according to the National Cancer Institute. There are nearly 5,000 deaths due to cervical cancer each year in this country. Recent data from NCI reveal that the number of cases of cervical cancer in white women under the age of 50 in the United States has been increasing 3 percent each year since 1986. In contrast, incidence rates are declining in black women of all ages and in white women over age 50. According to the World Health Organization, cervical cancer is also the most common cancer among women in developing countries. New technologies available now may enhance the value of the Pap test, but for women the most important step is getting screened.

Early Detection Gives Time for Treatment

Most cervical cancers gradually progress over a period of years without immediately invading nearby tissue. Yet they leave telltale signposts along their way. Even the transition from a normal to a cancerous cervical cell is usually a gradual one, with several steps that can be seen with the aid of a microscope.

In what is thought to be one of the first steps in the development of cervical cancer, the nuclei of cervical cells enlarge and darken. A patch of these abnormal cells is termed a squamous intraepithelial lesion (SIL) because the abnormal cells are present only in the squamous epithelial cells which line the surface of the cervix. SILs are further classified as low-grade if the abnormal cells are of normal size, or high-grade if the cells are smaller than normal.

Low-grade SILs are common; most spontaneously revert to normal. But because some will progress to high-grade SILs and then to cervical cancer, most doctors ask women with this Pap diagnosis to have Pap tests every four to six months for about two years. After three consecutive Pap tests come back negative, women can return to a routine screening protocol.

If repeated Pap tests show persistent abnormalities, however, a woman's doctor may want to confirm the low-grade SIL diagnosis by further scrutinizing the cervix with other procedures.

Colposcopy is a widely used method to check the cervix for abnormal areas. The doctor applies special stains to the cervix and then uses an instrument much like a microscope (called a colposcope) to detect abnormal cells, which turn a different color than healthy cells.

The doctor also may want to remove a small amount of cervical tissue for examination with a biopsy. It also may be necessary to scrape more tissue from inside the cervical opening. These procedures can be done in the doctor's office under local anesthesia.

If the low-grade SIL diagnosis is confirmed, a doctor may ask the patient to continue to have frequent Pap tests. Alternatively, the doctor may prefer to destroy the abnormal area by freezing it (cryosurgery), burning it (cauterization), or by removing it with a laser or electrosurgical device. Such treatment may cause cramping or other pain, bleeding, or a watery discharge.

High-grade SILs rarely regress spontaneously. Most progress to cervical cancer over a period of 10 to 15 years, according to the National Cancer Institute. Women who have high-grade SIL Pap reports usually are asked to undergo a colposcopy or biopsy procedure to confirm diagnosis. Once the high-grade SIL diagnosis is certain, doctors usually destroy the lesion with one of the procedures described in the previous paragraph. Or, the lesion and adjacent tissue may be surgically removed.

If a high-grade SIL progresses to the point that the cell nuclei become jagged or irregular in shape, extremely dark, and enlarged, and the cells themselves are strangely shaped (tadpole- or spindle-shaped, for example, instead of round), the lesion is considered cancerous. If the cancer is limited in scope, it may be treated with some of the same methods used to destroy precancerous lesions. For more widespread cancers, more involved surgery is usually done, removing a larger portion of the cervix or the entire uterus, ovaries or fallopian tubes. Depending on the size and location of the tumor, radiation therapy or chemotherapy may also be necessary.

About the Author

www.fda.gov
FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.