NEW YORK (GenomeWeb News) – Genetic testing for human papillomavirus or HPV followed by conventional cytology in HPV-positive women may be an effective primary cervical cancer screening method — particularly in women 35 or older — according to a paper published online today in the Journal of the National Cancer Institute.
Finnish researchers compared the Qiagen Hybrid Capture 2 HPV test with conventional cytology screening, also known as Papanicolaou or Pap testing, in more than 100,000 women between the ages of 25 and 65 years old.
Based on their findings, the team concluded that the HPV test — used in conjunction with cytology for HPV positive women — was a more sensitive primary screening tool than cytology but lacked some specificity for detecting authentic cancerous or pre-cancerous lesions in women under 35 years old. In contrast, the researchers reported, both sensitivity and specificity were high when the HPV test was used for women 35 and older.
"[O]ur results support the use of HPV DNA testing with cytology triage in primary cervical screening," senior author Ahti Anttila, a researcher with the Finnish Cancer Registry in Helsinki, and co-authors wrote. "The cross-sectional performance of primary HPV DNA screening with cytology triage was similar to that of conventional screening and was particularly good among women aged at least (or preferably older than) 35 years."
HPV infections are a well-known risk factor for cervical cancer or pre-cancerous cervical intraepithelial neoplasia (CIN) lesions, though many HPV infections resolve without causing cancer-related problems.
Genetic tests for HPV — such as Qiagen's Hybrid Capture 2 test, which detects more than a dozen high-risk HPV strains — are increasingly being explored for their use in cervical cancer screening programs.
For example, a study published in the New England Journal of Medicine this spring found that the HPV genetic test curbed cervical cancer deaths better than Pap tests or visual screening in a previously unscreened population in rural India.
And in March researchers from Kaiser Permanente and the National Cancer Institute concluded that adding HPV genetic testing to existing cytology-based screening programs did not lead to excessive false positive tests.
On the other hand, a randomized clinical trial by British researchers, published online in Lancet Oncology in June concluded that such co-testing, using both the HPV test and conventional cytology together, was not cost effective.
For the latest study, the researchers decided to evaluate the HPV DNA test as a primary screening tool in Finland, where women between the ages of 30 and 60 years old are usually invited for cervical cancer screening every five years.
The team attempted to compare HPV tests (using cytology as a follow-up in HPV-positive cases) with cytology in 108,425 women between the ages of 25 and 65 years old over two years. Women from both groups were referred for colposcopy testing if cytology revealed low-grade or more serious CIN lesions.
About half of the women — 52,207 — were randomly invited for HPV DNA testing with the Qiagen Hybrid Capture 2 assay while the other half — 54,218 — were invited to receive conventional cytology screening. Roughly 66 percent of those in each group actually attended screening and 2,737 of women invited for HPV testing received cytology instead.
In the HPV genetic testing group, 7.2 percent of women were ultimately recommended for follow-up testing compared with 6.6 percent in the cytology group. And, the team reported, they found 37 percent more lesions or cervical cancers in the HPV test group overall.
Of the 424 women referred for colposcopy in the HPV test group, the researchers detected 213 CIN lesions or cancer cases. Meanwhile in the cytology arm of the study, 420 women were referred for colposcopy and 154 were diagnosed with CIN lesions or cancer.
But the team also found age-specific differences in the relative sensitivity and specificity of each screening method. In those under 35 years old, women from the HPV test group were much more likely to be referred for follow-up than women in the cytology group. For instance, in the 25- to 29-year-olds, nearly 22 percent of women from the HPV test group were recommended for follow up compared with ten percent in the cytology group.
While the sensitivity of the HPV test was similar to — or higher than — that in the cytology screening arm, the specificity of the HPV test only appeared to be superior to cytology in women who were 35 and older.
Based on their findings, the researchers called for additional studies to assess the effectiveness of HPV genetic testing as a routine screening method for women younger than 35 years old as well as the potential of using HPV testing without cytology follow-up.
In an editorial appearing in the same issue of JNCI, McGill University oncology researcher Eduardo Franco, who has served on the board member or consultant for several companies involved in HPV vaccine development, HPV diagnostics, or cervical cancer cytology screening in the past, touted the study for examining HPV testing as a primary screening approach.
"The central finding of this landmark study is that the sequential (rather than parallel) use of HPV DNA screening followed by Papanicolaou triage not only permits enhanced detection of high-grade pre-cancers but also achieves better specificity than the traditional strategy of cytology-only screening," Franco wrote.
"Not surprisingly, restricting the analyses to women aged 35 years or older improved the screening indices substantially for the intervention arm relative to standard practice (i.e., cytology only)," he added.
Franco also suggested that objective molecular tests such as the HPV test may become even more important for finding abnormal cytological patterns as more and more women who have received HPV vaccines reach cervical cancer screening age.