Some postmenopausal women may not need to have Pap smears within two years of a normal test result, a University of California, San Francisco study has found. This is because it is unlikely these women will have significant abnormalities within that time frame, the researchers said.
Moreover, the test-used to screen for abnormal cells that could lead to cervical cancer if untreated-is far more prone to give a false-positive reading rather than detect early cervical disease in this group of women. A false positive result is when the test suggests clinically important changes when there are none.
"The bottom line is in postmenopausal women who have normal Pap smear results, the benefits of annual screening appear to be small and the risk of false-positive testing is many orders of magnitude greater," said study author George Sawaya, MD, UCSF assistant professor of obstetrics, gynecology and reproductive sciences. The study will be published in the December 19 issue of the Annals of Internal Medicine.
The incidence of cervical cancer has declined by more than 70 percent in the U.S. over the last 50 years. The widespread availability of Pap smears is credited for that drop. It is standard practice to screen women every one to three years in the U.S. But, there is no consensus on when-or if--screening should stop. Recommendations from different professional groups range from discontinuing screening at 65 years of age in previously screened women with a history of normal smears to less frequent screening at undefined intervals.
"No one knows how often to screen postmenopausal women for cervical cancer," Sawaya said. "But we do know that if women have been screened throughout their lives and have tested negative for cervical abnormalities, the chance that they will develop new cervical disease is quite small. But no one has tried to quantify this likelihood in postmenopausal women in the United States. This is the first study to do that."
The study included 2,561 women enrolled in the Heart and Estrogen/progestin Replacement Study (HERS). The mean age was 66.7 years old. One year after a normal base line Pap smear, 78 women (three percent) had an abnormal smear. An additional 32 women (1.4 percent) had an abnormal smear two years later. Most tests detected minor cellular changes. The follow up procedures on these women included repeat Pap smears, colposcopy (using an instrument to take a magnified view of the cervix) and biopsy (removal of sample tissue to see if abnormal tissue is present). A total of 231 interventions were performed.
Researchers found only one woman to have a cervical lesion within two years of the baseline smear. The rest of the women turned out to have false-positive results, meaning no clinically significant abnormalities were found on their cervix.
Sawaya and the other study authors say the danger of false-positive testing is that it can cause undue stress on a patient, needless concern and unnecessary medical procedures. Given these adverse effects, health care providers should be cautious about applying tests that have a high likelihood of yielding false-positive results, the authors assert.
"Postmenopausal women with a history of many normal smears who decide with their providers to be screened annually need to be aware of the risks of false-positive testing," Sawaya said. "They should be more informed."
The study also examined whether oral hormone replacement therapy had any effect on the development of cervical cellular abnormalities. Researchers found hormone replacement therapy did not significantly affect the incidence of abnormalities over the two year period.
The American Cancer Society predicts there will be about 12,800 new cases of invasive cervical cancer this year and about 4,600 women will die from the disease. Most cases occur in women who have never been screened at all. Before widespread screening, cervical cancer used to be one of the most deadly cancers for American women.
"Most women who get cervical cancer in the United States and who die from it are over 50 years old, but that is largely due to the fact that they have never been screened or not recently screened," Sawaya said. "This means a woman who has a long history of normal Pap smears and who is over 50 years old has a very low risk of developing new cervical disease. We should be focusing more of our efforts on screening unscreened and poorly-screened women."
The most important risk factor for cervical cancer is infection with human papillomavirus (HPV), a disease that can be passed from one person to another during sex. Having unprotected sex and having many sexual partners (or having sex with men who have had many sexual partners) makes HPV infection more likely in women, according to the American Cancer Society. Smoking is another risk factor for cervical cancer.
Other UCSF study authors are Deborah Grady, MD, MPH, professor and vice-chair of epidemiology and biostatistics and Karla Kerlikowske, MD, assistant professor in residence of general internal medicine. Additional authors are June La Valleur, MD, University of Minnesota; Vanessa M. Barnabel, MD, PhD, Medical College of Wisconsin; Katherine Bass, MD, Fertility Center of Maryland; Thomas E. Snyder, MD, Wake Forest University School of Medicine; James H. Pickar, MD, Wyeth-Ayerst Research; Sanjay K. Agarwal, MD, Cedars-Sinai Medical Center; and Jeanne Mandelblatt, MD, MPH, Georgetown University Medical Center.
The study was funded by grants from the Rhoda Goldman Fund of Mount Zion Health Systems; American College of Obstetricians and Gynecologists/Solvay Pharmaceuticals Inc.; National Cancer Institute; National Institute on Aging; and the Agency for Healthcare Research and Quality. The HERS study was funded by Wyeth-Ayerst Research.
Journal
Annals of Internal Medicine