HPV testing superior to Pap, safe to extend screening to once every 3 years

Results from a study of more than 330,000 women showed that most can safely undergo screening for cervical cancer once every 3 years, according to data presented Wednesday at a press conference in advance of the 2011 ASCO Annual Meeting.

Additionally, the findings demonstrated that HPV testing alone is more accurate than Pap smear for determining cervical cancer risk. HPV testing was “clearly superior” to Pap smear for predicting who would develop severe dysplasia or cancer within 5 years, although Pap smear detected additional HPV-positive women with cancer or precancer.

Screening guidelines from the American College of Obstetricians and Gynecologists and ACS endorse concurrent HPV testing with Pap tests as an alternative to Pap testing alone for women aged at least 30 years and recommend co-testing every 3 years for women who are HPV-negative and have a normal Pap test.

Hormuzd A. Katki, PhD, principal investigator in the division of cancer epidemiology and genetics at the NCI, called the results “a formal confirmation” of the safety of 3-year follow-up for women who have a negative HPV test and normal Pap result.

“A single negative HPV test provided 5 years of extremely low cancer risk for women, and this risk was not appreciably lowered by also having a normal Pap test,” he said. “These findings directly demonstrate the safety of current guidelines, which recommend a 3-year screening interval for women who test negative for HPV.

“Furthermore, these findings suggest that all HPV-negative women could safely return no earlier than 3 years,” Katki said.

For 5 years, researchers followed 331,818 women aged at least 30 years who enrolled in Kaiser Permanente Northern California’s co-testing program between 2003 and 2005. Five-year cancer risk for HPV-negative women with a normal Pap test was 3.2 per 100,000 women per year.

HPV-negative women had half the cancer risk of women with a normal Pap test, 3.8 per 100,000 women per year vs. 7.5 per 100,000. Cancer risk for HPV testing alone was similar to HPV and Pap testing together, 3.8 per 100,000 women per year vs. 3.2 per 100,000 women per year.

HPV testing also identified more women at high risk for cervical cancer. Regardless of Pap or HPV test results, women who were HPV-positive at enrollment had a higher 5-year risk for cervical cancer or precancer than women with an abnormal Pap test at enrollment, 1.5% per year vs. 0.9% per year.

The 5-year risk for developing cancer or precancer was 7.6% in women who were HPV-positive compared with 4.7% for women who were HPV-negative, for an excess risk of 7.4%. Katki said women who were HPV-negative had a lower risk for developing cancer or precancer than women who had negative Pap results.

“This shows that the HPV test is better for separating women into categories of high risk for cancer and low risk for cancer,” he said. “However, that does not mean that a Pap test was useless. When we combine HPV testing and Pap testing, we can get something even better.”

Katki said the Pap test did not tell HPV-negative women much about their risk, but for women who were HPV-positive, the Pap test discovered an additional 6% of women who had cancer or precancer.

“Most of that extra 6% were found at enrollment into the co-testing program, which shows that the Pap test is able to identify women who have immediate disease, whereas women who were negative for the Pap test but HPV-positive may develop cancer or precancer, but likely at some point off in the future,” he said. – by Jason Harris

For more information:

• Katki HA. #1508. To be presented at: 2011 ASCO Annual Meeting; June 3-7, 2011; Chicago.

The data presented certainly support the argument that if you are a woman who is HPV-negative and Pap smear-negative, a test every 3 years would be reasonable. It is not surprising to say that HPV testing alone would be potentially better than Pap smear alone because we know that almost all cervix cancer is caused by HPV, but I would not agree nor do I think the authors are saying that we should not perform a Pap smear. These data do not suggest that a Pap smear is not a cost-effective test or that the HPV test should be the standard. Before one would change any established practice, we would need to see a peer-reviewed paper.

– Maurie Markman, MD
HemOnc Today Editorial Board member

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