NEW YORK — Since Pap smears became routine in the United States in the 1940s, the number of women who die from cervical and related cancers has declined by 70%.
But health officials are still trying to determine how often the cancer screening test should be performed.
The American Cancer Society recommended that women have the test two years in a row and then every three years if their results are normal. Recently, the organization revised its guidelines and suggested that after a woman has three annual Pap smears that are normal, it is up to her doctor to decide how soon to perform the next one.
Question of Risk
"A woman who is at high risk for cervical cancer would need to have it performed more often than a woman who has no known risks," said Dr. Robert V. P. Hutter, chairman of the society's committee on cancer prevention. "A 45-year-old prostitute is at higher risk than a woman who has had a hysterectomy for unrelated causes."
The society estimates that 13,000 women will get cervical cancer this year and 6,800 will die from it. The 15% to 20% of American women who do not have regular Pap smears account for the majority of those who die.
In a Pap smear, a small sample of cells is swabbed off the cervix and lining of the uterus and examined under a microscope. A trained technician or physician can detect abnormal changes in cells that may be precursors to cervical cancer.
It may take 20 years from the earliest cellular changes to full-blown cancer, Hutter said. But he said the average is about 10 years. It is estimated that only 5% of cervical cancers develop rapidly.
Because of that, only 2% of early cervical cancers will be missed if women have Pap smears every two years instead of annually, and 5% will be missed if women have them every three years.
Hutter said some government agencies recommend less frequent Pap smears out of a desire to get the most from the limited amount of money available for preventive health care.
Doctors said women who can afford annual examinations with a private doctor may choose to have annual Pap smears to be absolutely safe. But public health facilities may perform the exams less frequently on women who are not at risk because the chances of missing an early cancer is not worth the cost of the procedure.
Dr. Diane Fink, a cancer society spokeswoman, said women who start engaging in sex at an early age or who have had multiple sexual partners are at higher risk for cervical cancer than women who lose their virginity late in life and have monogamous relationships.
She said doctors are not positive why women with multiple partners are at risk, but an increasing body of evidence suggests that a virus may cause the cancer.
The virus, the papilloma variety, is sexually transmitted, which would suggest that women with a number of partners may increase their chance of coming in contact with it.
Although there is no proof, researchers have also suggested that the virus causes more damage in young women, which would explain why early sexual activity increases a woman's chances of getting the cancer.
Fink said cigarette smoke also appears to be a risk factor in cervical cancer, although the reasons are not clear.
"Cigarette smoking does seem to promote the development of cervical cancer," she said.
"The key to all of this is the Pap smear. If (cancer) is caught early, it can be treated."
Hutter said that when the test detects abnormal cells in the cervix, there are a number of procedures that can take care of the problem. He said cryosurgery, the use of liquid nitrogen to remove a layer of cells from the surface of cervix, is becoming increasingly favored.
Health groups like the National Cancer Institute, the American College of Obstetricians and Gynecologists and other health organizations almost all recommend that a woman have her first Pap smear when she becomes sexually active, or when she reaches age 18.
Doctors said annual exams are important initially to obtain a reading of normal cells, with which comparisons can be made in the future.