Cervical cancer is cancer of the uterine cervix (the tip of the uterus that extends into the vagina).
Invasive cervical cancer accounts for 2.5 percent of all cancers that afflict women in the U.S. About 13,500 cases of invasive carcinoma of the cervix are diagnosed in the U.S. each year, while there are at least 50,000 new cases of a pre-invasive cancer, known as carcinoma in situ, where the cancer cells are confined to the surface skin of the cervix.
Since 1940, there has been a steady decrease in the incidence of carcinoma of the cervix because most women with no symptoms are screened with cervical and vaginal Pap smears. The probability at birth that a white woman will eventually develop cervical cancer dropped from 1.1 percent in 1975 to 0.7 percent in 1985. Similarly, for black women, the probability dropped from 2.3 percent in 1975 to 1.6 percent in 1985. Overall, mortality declined 45 percent between 1992 and 1994 and, because of increased effectiveness of screening procedures, continues to drop to this day.
Over 90 percent of cervical carcinomas start in the surface cells lining the cervix and are called squamous cell carcinoma. About 5 to 9 percent start in glandular tissue and are called adenocarcinoma. Adenocarcinomas are more difficult to diagnose, but they are treated the same way as squamous cell carcinomas and the survival rate, stage for stage, is similar.
There are several types of adenocarcinoma. About 60 percent are the endocervical cell type, 10 percent are each endometrioid and clear cell carcinomas, and 20 percent are adenosquamous carcinoma.
There are two rare types of cervical carcinoma, known as small cell carcinoma and cervical sarcoma. Both have a poor prognosis.
Most scientists believe that cervical warts or pre-invasive cervical cancer may develop over a period of months or years after the cervix is infected with the human papilloma virus (HPV). This early tumor, known as mild dysplasia or cervical intraepithelial neoplasia (CIN-1) or Grade 1, can progress to moderate dysplasia (CIN-2), then to severe dysplasia and carcinoma in situ (CIN-3) and eventually to invasive carcinoma. Most physicians believe that about two-thirds of all cases of severe dysplasia will progress to invasive cancer if left untreated. This transformation takes anywhere from 3 to 30 years; about 10 years on the average.
Once the cervical cancer becomes invasive, it can spread locally to the upper vagina and into the tissues surrounding the upper vagina and the cervix (the parametrium). Eventually, it grows toward the pelvic sidewall, obstructing the tubes (ureters) that drain urine from the kidney to the bladder. It can also spread to the bladder and rectum.
Cervical tumor cells can invade the lymphatic system and spread to the lymph nodes in the pelvic wall. Eventually they may spread to the iliac lymph nodes higher in the pelvis, the aortic lymph nodes, the nodes above the collarbone and occasionally to the groin nodes.
Metastases can also spread through the bloodstream to the outer vagina, vulva, lungs, liver and brain. Invasion of the pelvic nerves is common in advanced cases. There may also be spread within the abdomen when the tumor penetrates the full thickness of the cervix.
In general, the major risk factors for cervical cancer appear to include initiation of sexual activity at an early age, multiple sexual partners (or a partner who has had multiple sex partners), infection with human papilloma virus 16, and cigarette smoking.
More than 90 percent of all cervical cancers are squamous cell carcinomas, and researchers believe that this cancer may be a sexually transmitted disease. There is much evidence that cervical carcinoma is related to sexually transmitted organisms.
Most researches believe that the human papilloma virus (HPV) is a strong cofactor in the development of pre-invasive and invasive carcinomas of the cervix, as well as pre-invasive and invasive squamous cell cancer of the vagina and vulva. Ninety to nintey-five percent of squamous cell carcinomas of the cervix contain the human papilloma virus DNA.
The virus is a sexually transmitted disease. There are more than 50 types of human papilloma virus (HPV) that infect humans. Types 6 and 11 usually cause warts, while types 16, 18, 31 and 33 usually result in high-grade cervical dysplasia (CIN-2 and CIN-3) and carcinomas. The virus infects the tissues of the lower genital tract and may produce obvious genital warts or mild, moderate or severe dysplasia and carcinoma in situ. Genital warts are associated with cervical, vaginal and vulvar dysplasia and invasive carcinoma (in 25 percent of all cases).
However, although infection with HPV does increase the risk of cervical cancer, many women infected by HPV do not go on to develop cervical cancer. Co-factors such as immune system functioning, nutrition and diet, hormones, smoking and other sexually transmitted diseases (STDs) are currently being evaluated by researchers.
Several factors can reduce the risk of cervical cancer a woman faces. In general, any steps to avoid sexually transmitted infection will reduce cervical cancer risk.
Lower than average risk is associated with:
- First intercourse deferred until age 18 to 20 or older
- Intercourse with only one male partner
- Use of condoms
- Use of a diaphragm
- Use of spermicide
- Circumcision and Jewish ethnicity, thought in the past to be protective factors, are now known to be unrelated to cancer risk (except to the extent that they correlate with sexual monogamy and abstinence before marriage).
Factors associated with higher than average cancer risk are:
- Previous CIN (cervical intraepithelial neoplasia, also called dysplasia)
- Genital wart virus infection (some strains)
- Previous vulvar or vaginal cancer
- Exposure to a male whose previous partner(s) had cervical cancer or CIN
- Exposure to a sexual partner who has (or had) penile cancer
- Exposure to more than one male sexual partner (compared to the risk for a woman with one lifetime partner, two partners increase the risk 250 percent; six partners, 600 percent)
- Smoking cigarettes
- DES (diethylstilbestrol) exposure during fetal development
- Birth control pills used four years or more
- Previous herpes, gonorrhea, syphilis or other sexually transmitted infections
- First intercourse before the age of 18 to 20
- First pregnancy before the age of 18 to 20
Pap tests are recommended to detect abnormal cervical tissue before it becomes cancerous. The American Cancer Society (ACS) recommends a yearly Pap test along with pelvic exam in women who are sexually active or who are over age 18 (ACS guidelines suggest that after three or more consecutive annual exams with normal findings, the Pap test may be performed less frequently at the discretion of the physician).
Treatment for very early cervical cancer depends on the age of the woman and on the preferences of the patient and her doctor. Treatment may involve cryosurgery, cauterization, conization, laser treatment or hysterectomy. Conization is the usual treatment for young women who wish to have children. Most women who do not want to have additional children are treated with total hysterectomy (removal of the cervix and uterus.)
Treatment for invasive cancer of the cervix depends on the extent of the disease. Patients whose cancer has invaded only the cervix and those whose disease has extended into the tissues next to the cervix or to the upper vagina can be treated effectively with either surgery or radiation therapy. Surgery may be a total hysterectomy or a radical hysterectomy (removal of the cervix, uterus, upper vagina and the lymph nodes in the area.) Both internal and external radiation therapy can be used to treat invasive cervical cancer.
Patients with cancer that has spread to the pelvis, the lower part of the vagina or to the ureter are treated with radiation therapy alone. Again, both internal and external radiation therapy can be used.
Patients with cervical cancer that has spread to the bladder, rectum or distant parts of the body, may receive chemotherapy in addition to surgery or radiation therapy. Chemotherapy also is used to treat patients whose disease recurs following treatment with surgery or radiation therapy.