HPV testing more effective than Pap smear for detecting cervical cancer

Cotesting women for cervical cancer using a combination of HPV test and Pap smear did not detect cancers that could not be identified by HPV screening alone, study data showed.

“Cervical cancer screening guidelines have changed profoundly over the last 10 to 15 years, following introduction of testing for the dozen HPV types that cause virtually all cervical cancer and its precursors,” Mark Schiffman, MD, MPH, of the division of cancer epidemiology and genetics at NCI, and colleagues wrote. “… Unfortunately, improved screening methods have introduced some confusion, even controversy.”

For instance, some gynecologists have continued to use cytology testing, or Pap smears, in addition to HPV testing, because — although rare — they fear missing HPV-negative, cytology-positive cervical cancers.

As HemOnc Today previously reported, draft guidance from the U.S. Preventive Services Task Force recommended primary HPV testing every 5 years or cytology every 3 years among women aged 30 to 64 years. The guidance recommended against cotesting.

 “The accumulated evidence supports inclusion of HPV testing in screening; thus, the main choice moving forward is between cotesting and primary HPV testing alone,” Schiffman and colleagues wrote.

The researchers reviewed data on the detection of cervical cancer and precancer from 1,208,710 women aged 30 years and older who underwent screening at Kaiser Permanente in Northern California between Jan. 1, 2003, and Dec. 31, 2015.

Schiffman and colleagues compared cancer detection by cotesting with HPV testing alone, and assessed how testing methods contributed to diagnosing cancers (n = 623) and precancers (n = 5,369).

The cancers detected included 351 (56.3%) squamous cell carcinomas, 212 (34%) adenocarcinomas, 41 (6.6%) microinvasive cancers and 19 (3%) other cancers.

Prediagnostic HPV testing appeared more clinically sensitive than cytology for identifying women later diagnosed with cancer (76.7% vs. 59.1%; P < .001) and precancer (83.8% vs. 61.9%; P < .001).

HPV testing also appeared more likely to identify cancer than cytology 12 months or longer before a cancer diagnosis (62.8% vs. 28.7% P < .001), but not immediately prior to a cancer diagnosis (89.2% vs. 86.2%). HPV was more likely to be positive less than 12 months prior to a precancer diagnosis (96.2% vs. 89.8%) and 12 or more months before a precancer diagnosis (70.6% vs. 32.4%; P < .001 for both).

A majority of prediagnostic cotests were positive by HPV and/or cytology for cancer (82.6%) and precancer (87.3%). However, only small fractions of precancer (3.5%) or cancer (5.9%) cases were detected by cytology alone. Researchers noted these cancers were mostly regional or distant stage with squamous histopathology.

The addition of cytology testing to HPV testing contributed to earlier detection of no more than five cases per million women screened each year.

More than half of women diagnosed with cancer (67.9%) or precancer (58.3%) during 10 years of follow-up had been detected by the first cotest.

 “The introduction of HPV testing alone as a cervical cancer screening option would perform nearly the same as HPV and cytology cotesting,” the researchers wrote. “Excessive screening in an attempt to prevent every case could have minimal cancer prevention benefits while increasing the harms of screening.” – by Andy Polhamus

Disclosures: NCI received results of cervical cytology and HPV testing results at reduced or no cost from Becton Dickinson and Roche. One author reports receiving HPV tests and biomarker assays for research at reduced or no cost from Arbor Vita Corporation, Becton Dickinson, Cepheid and Roche.