Reflection and Reaction

Trials comparing cytology with human papillomavirus screening

The development of human papillomavirus (HPV)-based screening should detect more pre-cancerous changes and so reduce the incidence and mortality from cervical squamous carcinoma and cervical adenocarcinoma. However, many more women are high risk HPV (hrHPV) screen positive compared to cytology-based screening, especially in younger age-women. A variety of tests have become available which may triage into those hrHPV test-positive women who need immediate referral to colposcopy from those who need early repeat HPV tests or recall on the basis of their disease status.

We performed a literature review of publications and a manual search from 2010, reporting cytology, HPV partial genotyping, dual-staining and DNA methylation for triage of hrHPV positive tests, including their comparative performance between these methods as well as the effectiveness of some triage combinations with reference to HPV-based screening services in Europe. Cost effectiveness and the structure of triage algorithms for colposcopists also have been considered. From one report evaluating four options for triage as single options or as combined algorithms, partial genotyping for HPV 16 and 18 with dual-staining yielded the highest risk of cervical intraepithelial neoplasia grade three or worse within an HPV positive population and with an acceptable colposcopy rate. From a separate paper, this option appeared cost effective. However, publications were difficult to compare objectively.

All options have their merits but a combination triage involving any two of cytology, HPV partial genotyping or dual-staining seems most efficient at present. HPV vaccination may impact upon the performance of future partial genotyping. DNA Methylation may become an acceptable future option.

In order to update the previous version of the European Code against Cancer and formulate evidence-based recommendations, a systematic search of the literature was performed according to the methodology agreed by the Code Working Groups. Based on the review, the 4th edition of the European Code against Cancer recommends:

“Take part in organized cancer screening programmes for:

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  Bowel cancer (men and women)

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  Breast cancer (women)

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  Cervical cancer (women).”

Organized screening programs are preferable because they provide better conditions to ensure that the Guidelines for Quality Assurance in Screening are followed in order to achieve the greatest benefit with the least harm. Screening is recommended only for those cancers where a demonstrated life-saving effect substantially outweighs the potential harm of examining very large numbers of people who may otherwise never have, or suffer from, these cancers, and when an adequate quality of the screening is achieved. EU citizens are recommended to participate in cancer screening each time an invitation from the national or regional screening program is received and after having read the information materials provided and carefully considered the potential benefits and harms of screening. Screening programs in the European Union vary with respect to the age groups invited and to the interval between invitations, depending on each country's cancer burden, local resources, and the type of screening test used

For colorectal cancer, most programs in the EU invite men and women starting at the age of 50–60 years, and from then on every 2 years if the screening test is the guaiac-based fecal occult blood test or fecal immunochemical test, or every 10 years or more if the screening test is flexible sigmoidoscopy or total colonoscopy. Most programs continue sending invitations to screening up to the age of 70–75 years.

For breast cancer, most programs in the EU invite women starting at the age of 50 years, and not before the age of 40 years, and from then on every 2 years until the age of 70–75 years.

For cervical cancer, if cytology (Pap) testing is used for screening, most programs in the EU invite women starting at the age of 25–30 years and from then on every 3 or 5 years. If human papillomavirus testing is used for screening, most women are invited starting at the age of 35 years (usually not before age 30 years) and from then on every 5 years or more. Irrespective of the test used, women continue participating in screening until the age of 60 or 65 years, and continue beyond this age unless the most recent test results are normal.

Cervical cancer precursor screening by HPV testing has a low positive predictive value for advanced lesion. HPV16 RNA patterns characteristic for HPV16-transformed cells but based on laborious, cost-intensive singleplex NASBA reactions promised high value in triaging HPV16 DNA-positive women.

We developed two high-throughput reverse transcriptase quantitative (RT-q) PCR assays for the HPV16 transcripts E6*I, E1^E4 and E1C and the cellular transcript ubiquitin C and analysed RNA of 158 singly HPV16 DNA-positive cervical cell samples archived in PreservCyt buffer for the presence of transformation-associated HPV16 RNA patterns, i.e., upregulation of E6*I relative to E1^E4 and/or presence of E1C.

HPV16 RNA pattern analyses classified 85% of 58 samples diagnosed ≤ CIN1 (no cytologically and histologically detectable cervical lesion or CIN grade 1) as negative and 90% of 59 samples diagnosed as ≥ CIN3 (CIN grade 3 or invasive cancer) as positive. Among 41 CIN grade 2 samples representing an intermediate lesion group, 49% were HPV16 RNA patterns-positive. Interestingly, 3 of 4 HPV16 RNA patterns-positive lesions initially diagnosed as ≤ CIN1 at follow-up 5–24 months later had progressed to ≥ CIN2.

We successfully developed and validated a second generation of HPV16 RNA patterns assay by rapid RT-qPCR as triage marker for HPV16 DNA-positive women offering clinical utility to distinguish between the need for immediate colposcopy and continued observation. Limited follow-up data suggests that HPV16 RNA patterns-positivity in ≤ CIN1 lesions can predict disease progression.

Colposcopy has a poor sensitivity to detect precancerous abnormalities of the cervix. These abnormalities will become less common after HPV vaccinated girls enter the screened population. However HPV-based screening is likely to result in more colposcopic referrals. Both these changes to cervical screening programs will reduce the incidence of high grade CIN and cervical cancer as well as the prevalence of high grade CIN presenting to the colposcopist. As a consequence the diagnostic performance of conventional colposcopy will be further challenged. This review aims to discuss leading technologies which are currently available as an alternative or in addition to colposcopy and may serve to improve the current colposcopic assessment of precancerous cervical abnormalities.

Cytology-based nation-wide cervical screening has led to a substantial reduction of the incidence of cervical cancer in western countries. However, the sensitivity of cytology for the detection of high-grade precursor lesions or cervical cancer is limited; therefore, repeated testing is necessary to achieve program effectiveness. Additionally, adenocarcinomas and its precursors are often missed by cytology. Consequently, there is a need for a better screening test. The insight that infection with high-risk human papillomavirus (hrHPV) is the causal agent of cervical cancer and its precursors has led to the development of molecular tests for the detection of hrHPV. Strong evidence now supports the use of hrHPV testing in the prevention of cervical cancer. In this review, we will discuss the arguments in favor of, and concerns on aspects of implementation of hrHPV testing in primary cervical cancer screening, such as the age to start hrHPV-based screening, ways to increase screening attendance, requirements for candidate hrHPV tests to be used, and triage algorithms for screen-positive women.

Widespread adoption of the Pap test as a screening tool for cervical cancer is arguably one of the most significant advances in public health in human history. While much of the basic performance of the Pap test has remained the same over the years, the addition of liquid-based cytology, automated image analysis, and concomitant testing for high-risk human papillomaviruses have had a substantial impact on the screening and treatment paradigm and the way the Pap test has been used over the last decade. These technologies have helped advance the detection of cervical cancer and its precursors.