CERVICAL CANCER

What Is Cervical Cancer? Cancer describes a number of illnesses all involving neoplasia, which means literally "new growth." When a normal cell becomes cancerous, it undergoes changes in its genetic material (DNA) that allow it to proliferate indefinitely, independently of the body's normal regulatory mechanisms. By replication, one cell eventually grows into a tumour, which can invade nearby healthy tissue, spread to distant sites, and ultimately interfere with the body's normal functioning. Cancer of the uterine cervix (the "neck" of the uterus) is the 2nd most common cancer of women worldwide, and accounts for 8000 deaths in North America annually. It is important to distinguish endometrial cancer (cancer involving a layer of the cells lining the inside of the uterus) from cervical cancer, since a number of significant differences exist between the behavior and management of each disease. The average age at diagnosis of cervical cancer is 51, but its incidence is increasing in young women, such that 25% of all patients with it are now younger than 35. In the case of endometrial cancer, the average age for Caucasian and black women is between 55 and 59 years. Fortunately, cervical cancer can largely be prevented through the implementation of screening programs (outlined below).

What Causes Cervical Cancer? Recent evidence has demonstrated that more than 95% of cases of cervical cancer are linked to infection with the human papilloma virus (HPV), the same virus responsible for genital warts. (Probably different strains of the virus are responsible for genital warts and cervical cancer.) Viruses multiply by injecting their DNA into the cells of their human hosts, thus providing a mechanism by which normal DNA can be altered. It is believed that HPV alone will not result in cancer; cofactors such as cigarette smoking and the presence of another infection are required to effect cancer development. HPV is transmitted through sexual contact, like any other sexually transmitted disease (STD), and thus women at risk of infection are those who become sexually active at an early age, have multiple partners, and have sexual contact with high-risk partners. HPV infection does not always result in clinical manifestations; in the case of cervical cancer, the progression from latent infection to carcinoma is usually a slow one, taking place over decades. Cervical cells pass through different stages of abnormality before becoming cancerous, and may regress to normal at any point, or continue toward carcinoma. It is these pre-cancerous stages, or precursor lesions, which can be detected by Pap smear and treated, thus pre-empting the development of cancer.

What Is The Likely Outcome Of Cervical Cancer? Happily, the outcome of cervical cancer is generally a good one, with a 65% five-year survival rate. An individual patient's prognosis is closely related to the stage or extent of illness (i.e. how deeply the tumour invades healthy tissue), and to the presence of cancer cells in neighbouring lymph nodes. (The lymphatic system is responsible for retrieving excess fluid from the body, filtering it, and returning it to the blood vessels, and thus provides a route by which cancer can spread; the presence of "positive nodes" indicates that this has already occurred.) Cervical cancer, if undetected, spreads (or metastasizes) most often by direct invasion of local tissue in the pelvis. It spreads less commonly via the lymphatic system, and very rarely through the blood, to sites more distant.

What Are The Signs And Symptoms Of Cervical Cancer? Cancerous cells will almost certainly be detected in any woman who has annual Pap smears long before she experiences symptoms. In the early stages of disease, more than 99% of patients will experience abnormal vaginal bleeding, particularly following intercourse. Late in the course of disease, bleeding may occur spontaneously (without provocation), pain may be felt in the pelvis or lower back, and the patient may experience bowel or bladder symptoms due to local spread. On physical exam, the cervix may appear enlarged, or the tumour may be obvious. Abnormal cells can be detected by Pap smear, a painless test in which the cervix is lightly scraped to remove a number of cells for microscopic examination. (See Prevention, below.)

What Is The Treatment For Cervical Cancer? Cancer of the cervix is treated by surgery, radiation therapy, or the two combined. Small, well-localized tumours that have neither spread to lymph nodes nor invaded neighbouring tissue can be removed surgically without the need for radiation. More extensive, invasive tumours will necessitate radiation therapy as well, in order to kill undetected malignant cells. (Chemotherapy is used more commonly in types of cancer more likely to spread via the blood.)

How Can Cervical Cancer Be Prevented? The incidence of cervical cancer worldwide is inversely proportional to the utilization of screening programs. Put simply, regular Pap smears can detect early stages of abnormality in cervical cells and allow for treatment of precursor lesions before the development of cancer transpires. All women should have an annual Pap smear from when they first become sexually active until approximately age 70. If abnormal cells are detected, a test for HPV will be performed, and the Pap smear will be repeated at a shorter interval. It is not uncommon for precursor lesions to regress or resolve spontaneously. However, two consecutive abnormal Pap smears indicate the need for colposcopy, a procedure allowing for direct visualization of the cervix by placing a small camera in the vagina. Lesions visible during colposcopy may be biopsied (sampled for analysis) or removed by cryotherapy (freezing), electrocautery (cauterization), or laser ablation. Proper assessment and management results in successful resolution of precursor lesions in 90% of women. Colposcopy is performed as an outpatient procedure, and complications are rare.