Papilloma viruses for cervical cancer

Larry H. Bernstein, MD, FCAP, Curator

LPBI

Practice Bulletin No. 131: Screening for Cervical Cancer

Study Backs Co-Testing for Cervical Cancer

A positive co-test result was more sensitive than either a positive HPV-only test or a positive Pap-only test.

http://www.medpagetoday.com/HematologyOncology/CervicalCancer/51016

Charles Bankhead

Cervical cancer screening with a test for human papillomavirus (HPV) resulted in a 50% higher rate of false-negative results versus Pap testing and three times greater versus co-testing, a large retrospective study showed.

Data encompassing more than 250,000 women showed a false-negative rate of 18.6% compared with 12.2% for Pap testing. With a false-negative rate of 5.5%, screening women with the HPV test and Pap test missed the fewest cancers.

The results support clinical guidelines that recommend co-testing, according to authors of a report in Cancer Cytopathology. The results differ dramatically, however, from those of previous studies that have consistently shown greater diagnostic accuracy for the HPV test compared with the Pap test.

“The reason that women are screened is that they want to be protected from cervical cancer,” study author R. Marshall Austin, MD, PhD, of Magee-Women’s Hospital and the University of Pittsburgh, told MedPage Today. “The previous trials have generally focused on cervical intraepithelial neoplasia 2 or 3, so-called precancer. The difference is that most of what we call precancer will actually never develop into cancer.

“The unique thing about this study, and what makes it so important, is that we looked at over 500 invasive cervical cancers, which are what women want to be protected against, and looked at the effectiveness of the methods of testing.”

A year ago, the FDA approved Roche’s cobas assay for HPV DNA as a first-line test for cervical cancer screening, following a unanimous vote for approval by an FDA advisory committee.

The approval was based primarily on a pivotal trial involving 47,200 women at high risk for cervical cancer. The primary endpoint was the proportion of patients who developed grade ≥3 cervical intraepithelial neoplasia (≥CIN3). The results showed a greater than 50% reduction in the incidence of ≥CIN3 with the DNA test versus Pap testing.

Austin and colleagues retrospectively analyzed clinical records for 256,648 average-risk women, ages 30 to 65, all of whom underwent co-testing as a screen for cervical cancer and subsequently had a cervical biopsy within a year of co-testing. The primary objective was to determine the sensitivity of the three screening methods for detection of biopsy-proven ≥CIN3 and invasive cancer.

The results showed that 74.7% of the women had a positive HPV test, 73.8% had an abnormal Pap test (atypical squamous cells of undetermined significance or worse), 89.2% had a positive co-test, and 1.6% had ≥CIN3.

Biopsy results showed that co-testing had the highest sensitivity for ≥CIN3 (98.8% versus 94% for HPV test only and 91.3% for Pap testing alone, P<0.0001). The Pap test had greater specificity versus HPV testing alone or co-testing (26.3% versus 25.6% versus 10.9%, P<0.0001).

Investigators identified 526 patients who developed biopsy-proven invasive cervical cancer. Of those patients, 98 tested negative by HPV assay only, 64 by Pap test only, and 29 by co-testing.

Given the average risk of the patient population included in the study, the results are broadly applicable to women in the age range studied, regardless of baseline risk for cervical cancer, Austin said.

The data also show that co-testing is better than either test alone, which supports current ACS recommendations for cervical cancer screening.

“The current approach, according to the American Cancer Society and 25 other organizations that worked with us on our last guideline, co-testing is the preferred strategy,” Saslow told MedPage Today. “This paper completely backs that up. Even though a Pap alone is acceptable, clearly, co-testing is the best way to go.”

Noting that only half of women in the U.S. do not under go co-testing despite clinical guidelines recommending it for more than a decade, Saslow asked, “What’s taking so long?”

Earlier this year, several organizations released joint “interim guidance” regarding cervical cancer screening. Described as an aid to clinical decision-making until existing guidelines are updated, the interim guidance characterized the HPV-DNA test as an acceptable alternative to Pap testing as a primary screening test.

In their article, Austin and colleagues argued that the HPV assay should be evaluated in comparison with the Pap test but as an alternative to co-testing.

“HPV-only primary screening for cervical cancer presents many challenges for clinicians,” the authors said. “Questions arise regarding its effectiveness, its long-term risk, and when it is the best option for a particular patient.

“Clinicians had similar questions when co-testing was first recommended for women 30 and older in 2006,” they added. “Since then the adoption of co-testing has steadily increased, with approximately 50% of physicians co-testing women 30 and older, but it is still not done at the recommended level.”

The study had some limitations. The authors could not confirm that the cervical biopsy results were from women who did not have an intervening screening test or treatment with a different provider during the study period.

Also, the authors were unable to draw conclusions based on the overall population of women who were screened for cervical cancer because the dataset consisted of screening results of women who underwent biopsies.