Approximately 16,000 women are diagnosed with cervical cancer each year in the United States, and 4800 women die from the disease annually (NCHS, 1998b). The 5-year survival rate is about 90% for women with localized cervical cancer but is only about 14% for women with advanced disease (NCHS, 1998b). The incidence of invasive cervical cancer has decreased greatly over the past 40 years, due largely to organized screening programs to detect early-stage disease (U.S. Preventive Services Task Force, 1996). Women with a history of multiple sexual partners, early age at onset of sexual intercourse, or both, are at highest risk of cervical cancer. Infection with HIV or some types of the human papilloma virus sharply increases risk.
The Pap smear is the principal screening test for cervical cancer. The U.S. Preventive Services Task Force, American Cancer Society, the National Cancer Institute, the American College of Obstetricians and Gynecologists, and the American Medical Association recommend that all women who are or have been sexually active, or who are 18 years of age or older, should have annual Pap smears. The recommendation permits Pap testing less frequently after 3 or more normal annual smears, at the discretion of individual physicians. There is no consensus on the age at which to discontinue Pap testing.
Colorectal cancer is the second-most-common form of cancer in the United States, after lung cancer, and is the second-leading cause of cancer death. Each year, about 140,000 new cases are diagnosed, and 55,000 persons die of the disease (NCHS, 1998b). The average patient who dies of colorectal cancer loses 13 years of life, and in addition to the mortality associated with this disease, its treatment can produce significant morbidity. Screening for early-stage colorectal cancer as well as its precursor lesions (adenomatous polyps) thus can significantly reduce morbidity and mortality associated with colorectal cancer.
Colorectal cancer screening can act as both primary and secondary prevention because the tests can detect and (in the case of sigmoidoscopy and colonoscopy) remove precancerous polyps as well as carcinomas. The principal tests for detecting polyps and early malignancy in asymptomatic persons are the fecal occult blood test (FOBT) and flexible sigmoidoscopy. There is a large literature on the accuracy and effectiveness of these