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British Study: Older Women Need Pap Smears Every Five Years; Younger Women Every Three Years (dateline November 5, 2003)

The results of a study by British researchers finds that older women need to be screened for cervical cancer once every five years while younger women should undergo screening once every three years. These guidelines differ from the American Cancer Society’s (ACS) suggestion of a yearly Pap smear for all women who are 18 years of age or older as well as for younger women who are sexually active. In fact, the current study finds little evidence for the need to screen women under age 25, since cervical cancer rarely occurs in these women. The study offers guidance for Britain’s cancer screening program.

Deaths from cervical cancer have declined dramatically in the United States and elsewhere in recent decades, largely from the increased use of the Pap smear to help detect cervical cancer in early stages. For example, there was a 74% decrease in the rate of cervical cancer in the U.S. between 1955 to 1992. When detected early, the five-year survival rate for cervical cancer is approximately 91%. Approximately 50 million Pap smears are performed each year in the United States. If cervical cancer is detected before it has invaded any surrounding tissues, the five-year survival rate is nearly 100%.

Most U.S. experts recommend that all women 18 years of age and older receive yearly Pap smears, as well as yearly pelvic exams. However, organizations such as the American Cancer Society say that physicians may perform Pap smears less often (once every three years) if the results of previous Pap smears are normal. In these cases, yearly pelvic exams are still recommended.

To determine the most effective interval for cervical cancer screening, British researchers led by Professor Peter Sasieni, of the charity, Cancer Research UK, studied the medical histories of 1,305 women aged 20-69 years who had been diagnosed with invasive cervical cancer. These individuals were then compared to healthy women who had never been diagnosed with cervical cancer.

For women between the ages of 55 and 69, the researchers found that screening for cervical cancer with a Pap smear once every five years is very effective at finding the disease in early stages, while screening every year provides only modest additional benefits. For women between the ages of 40 and 54, a Pap smear once every three years is nearly as effective at detecting cervical cancer as a yearly exam.

Pap smears once every three years were less effective in younger women (between the ages of 20 and 39), compared to women ages 40 to 54. According to the researchers, this calls into question the benefit of screening younger women for cervical cancer, since the disease is uncommon in these women and Pap smears are often associated with false positive results (i.e., they wrongly indicate that a patient has cancer; additional testing is required to resolve the error). At the same time, the study affirms the need to screen middle-aged women for cervical cancer.

Professor Sasieni and his colleagues explain that older women need less frequent Pap smears since the rate of cervical cancer growth in women over 55 tends to be much slower than in younger women. Thus, a Pap smear once every five years is still effective at detecting cervical cancer at an early stage when it is highly treatable.

The findings of the study are meant to provide guidance for Britain’s NHS Screening Programme. American women are still recommended by the American Cancer Society to receive Pap smears once every year or every three years, as determined by their physicians.

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