Cervical Cancer Screening Every 3 Years for Most Women

From Medscape Medical News
Roxanne Nelson

May 19, 2011 — A single test for the human papillomavirus (HPV) was found to be superior in predicting cervical cancer or high-grade cervical intraepithelial neoplasia than a single Pap test, according to a new study.

The results, which were highlighted at a press briefing held in advance of the annual meeting of the American Society of Clinical Oncology (ASCO), confirmed that for women with a negative HPV test and normal cytology, a 3-year follow-up appears to be safe and appropriate.

Women who tested negative for HPV had a 5-year cancer risk that was similar to those who tested negative for HPV and had normal cytology (3.8 vs 3.2 per 100,000 women per year; P = .8). This was half the cancer risk of women who had a negative result on Pap testing only (3.8 vs 7.5 per 100,000 women per year; P = .3).

Concurrent HPV testing and cervical cytology (cotesting) is an approved and promising alternative to cytology alone in women 30 years and older. Screening guidelines from organizations such as the American College of Obstetricians and Gynecologists and the American Cancer Society have endorsed the use of cotesting in this age group as a safe alternative to Pap testing alone.

Safety Data Lacking

However, the authors note that broad acceptance of cotesting has been hindered by a lack of evidence supporting its performance in routine clinical practice, especially related to the safety of 3-year screening intervals for women who test negative for HPV and have normal cytology results.

"Data are lacking on the safety of these guidelines in routine clinical practice," said lead author Hormuzd Katki, PhD, from the division of cancer epidemiology and genetics at the National Cancer Institute (NCI). "In particular, we need to know the actual cancer rates with cotesting, especially for women who test negative for HPV and have a normal Pap test."

Dr. Katki noted that his group at the NCI has been collaborating with Kaiser Permanente in Northern California, which began a cotesting program in 2003. In their study, Dr. Katki and colleagues obtained data on 331,818 women 30 years and older who enrolled in Kaiser's cotesting program from 2003 to 2005, and who were followed through 2009.

The women were categorized by their HPV and Pap test results at enrollment, explained Dr. Katki. "Then we estimated 5-year cumulative rates of cervical precancer and cancer."

5-Year Risk for Cancer/Precancer by Test Results
Test Results 5-Year Risk (%) Excess Risk (%)
HPV positive 7.6 7.4
HPV negative 0.2
Pap positive 4.7 4.3
Pap negative 0.4
HPV positive/Pap positive 12.0
HPV positive/Pap negative 6.0
HPV negative/Pap positive 0.9
HPV negative/Pap negative 0.2

Pap Test Not Obsolete

HPV testing identified more women who were at high risk for cervical cancer than Pap testing. "Women who tested HPV positive at enrollment had higher 5-year risks of developing cervical cancer or precancer than women with an abnormal Pap test at enrollment," said Dr. Katki, "and vice versa. Women who tested HPV negative had a lower risk of developing cancer or precancer" than those who had normal cytology results.

This shows that the HPV test is better able to separate those who are at high risk for cancer from those who are at low risk, he noted.

But Dr. Katki emphasized that the Pap test is not useless. Pap tests remain useful for triaging women with positive HPV tests, and can identify women with immediate disease.

Dr. Katki concluded that this study shows that a negative HPV test provides 5 years of an extremely low risk for cancer; the risk was not appreciably lowered by a negative Pap test. The data suggest that all women who test negative for HPV can safely extend their screening interval to at least 3 years.

"The data presented us with a strong hypothesis that will need to be tested in practice: Instead of doing cotesting, we could do HPV testing," and ask those with negative results to extend their screening interval to at least 3 years, Dr. Katki explained.

"Pap testing would then be reserved only for those in the HPV-positive population," he said. "In the Kaiser population, this would have reduced the number of Pap tests by 95% and could potentially retain all of the safety of cotesting."

Real-World Data

Comoderator George W. Sledge Jr, MD, president of ASCO, noted that he found this to be a "wonderful population-based study from a large real-world experience."

"It also tells us not just where we're going with cervical cancer, but perhaps with cancer screening in general," said Dr. Sledge, who is Ballve-Lantero Professor of Oncology and professor of pathology and laboratory medicine at the Indiana University School of Medicine, Indianapolis. "It is a switch from our classic approach of using now-ancient techniques of cytopathology to more molecular-based techniques that allow us to actually look at the specific cause of cancer in patients with cervical carcinoma."

Dr. Sledge noted that he "suspects that we'll see this again and again as we look at screening going forward for other diseases."

"This is going to be increasingly important — not just to medical oncologists, but also to all those who take care of these women," he said.

Annual Meeting of the American Society of Clinical Oncology. Abstract 1508. To be presented June 6, 2011.