Human papillomavirus and cervical cancer

Cervical cancer is the second most common cancer in women worldwide, and knowledge regarding its cause and pathogenesis is expanding rapidly. Persistent infection with one of about 15 genotypes of carcinogenic human papillomavirus (HPV) causes almost all cases. There are four major steps in cervical cancer development: infection of metaplastic epithelium at the cervical transformation zone, viral persistence, progression of persistently infected epithelium to cervical precancer, and invasion through the basement membrane of the epithelium. Infection is extremely common in young women in their first decade of sexual activity. Persistent infections and precancer are established, typically within 5-10 years, from less than 10% of new infections. Invasive cancer arises over many years, even decades, in a minority of women with precancer, with a peak or plateau in risk at about 35-55 years of age. Each genotype of HPV acts as an independent infection, with differing carcinogenic risks linked to evolutionary species. Our understanding has led to improved prevention and clinical management strategies, including improved screening tests and vaccines. The new HPV-oriented model of cervical carcinogenesis should gradually replace older morphological models based only on cytology and histology. If applied wisely, HPV-related technology can minimise the incidence of cervical cancer, and the morbidity and mortality it causes, even in low-resource settings.

American Cancer Society, American Society for Colposcopy and Cervical Pathology, and American Society for Clinical Pathology screening guidelines for the prevention and early detection of cervical cancer

An update to the American Cancer Society (ACS) guideline regarding screening for the early detection of cervical precancerous lesions and cancer is presented. The guidelines are based on a systematic evidence review, contributions from 6 working groups, and a recent symposium cosponsored by the ACS, the American Society for Colposcopy and Cervical Pathology, and the American Society for Clinical Pathology, which was attended by 25 organizations. The new screening recommendations address age-appropriate screening strategies, including the use of cytology and high-risk human papillomavirus (HPV) testing, follow-up (eg, the management of screen positives and screening intervals for screen negatives) of women after screening, the age at which to exit screening, future considerations regarding HPV testing alone as a primary screening approach, and screening strategies for women vaccinated against HPV16 and HPV18 infections.

Annual Report to the Nation on the Status of Cancer, 1975-2009, featuring the burden and trends in human papillomavirus(HPV)-associated cancers and HPV vaccination coverage levels

Background

The American Cancer Society (ACS), the Centers for Disease Control and Prevention (CDC), the National Cancer Institute (NCI), and the North American Association of Central Cancer Registries (NAACCR) collaborate annually to provide updates on cancer incidence and death rates and trends in these outcomes for the United States. This year’s report includes incidence trends for human papillomavirus (HPV)–associated cancers and HPV vaccination (recommended for adolescents aged 11–12 years).

Methods

Data on cancer incidence were obtained from the CDC, NCI, and NAACCR, and data on mortality were obtained from the CDC. Long- (1975/1992–2009) and short-term (2000–2009) trends in age-standardized incidence and death rates for all cancers combined and for the leading cancers among men and among women were examined by joinpoint analysis. Prevalence of HPV vaccination coverage during 2008 and 2010 and of Papanicolaou (Pap) testing during 2010 were obtained from national surveys.

Results

Death rates continued to decline for all cancers combined for men and women of all major racial and ethnic groups and for most major cancer sites; rates for both sexes combined decreased by 1.5% per year from 2000 to 2009. Overall incidence rates decreased in men but stabilized in women. Incidence rates increased for two HPV-associated cancers (oropharynx, anus) and some cancers not associated with HPV (eg, liver, kidney, thyroid). Nationally, 32.0% (95% confidence interval [CI] = 30.3% to 33.6%) of girls aged 13 to 17 years in 2010 had received three doses of the HPV vaccine, and coverage was statistically significantly lower among the uninsured (14.1%, 95% CI = 9.4% to 20.6%) and in some Southern states (eg, 20.0% in Alabama [95% CI = 13.9% to 27.9%] and Mississippi [95% CI = 13.8% to 28.2%]), where cervical cancer rates were highest and recent Pap testing prevalence was the lowest.

Conclusions

The overall trends in declining cancer death rates continue. However, increases in incidence rates for some HPV-associated cancers and low vaccination coverage among adolescents underscore the need for additional prevention efforts for HPV-associated cancers, including efforts to increase vaccination coverage.

Interobserver reproducibility of cervical cytologic and histologic interpretations: realistic estimates from the ASCUS-LSIL Triage Study

CONTEXT

Despite a critical presumption of reliability, standards of interpathologist agreement have not been well defined for interpretation of cervical pathology specimens.

OBJECTIVE

To determine the reproducibility of cytologic, colposcopic histologic, and loop electrosurgical excision procedure (LEEP) histologic cervical specimen interpretations among multiple well-trained observers.

DESIGN AND SETTING

The Atypical Squamous Cells of Undetermined Significance-Low-grade Squamous Intraepithelial Lesion (ASCUS-LSIL) Triage Study (ALTS), an ongoing US multicenter clinical trial.

SUBJECTS

From women enrolled in ALTS during 1996-1998, 4948 monolayer cytologic slides, 2237 colposcopic biopsies, and 535 LEEP specimens were interpreted by 7 clinical center and 4 Pathology Quality Control Group (QC) pathologists.

MAIN OUTCOME MEASURES

kappa Values calculated for comparison of the original clinical center interpretation and the first QC reviewer's masked interpretation of specimens.

RESULTS

For all 3 specimen types, the clinical center pathologists rendered significantly more severe interpretations than did reviewing QC pathologists. The reproducibility of monolayer cytologic interpretations was moderate (kappa = 0.46; 95% confidence interval [CI], 0.44-0.48) and equivalent to the reproducibility of punch biopsy histopathologic interpretations (kappa = 0.46; 95% CI, 0.43-0.49) and LEEP histopathologic interpretations (kappa = 0.49; 95% CI, 0.44-0.55). The lack of reproducibility of histopathology was most evident for less severe interpretations.

CONCLUSIONS

Interpretive variability is substantial for all types of cervical specimens. Histopathology of cervical biopsies is not more reproducible than monolayer cytology, and even the interpretation of LEEP results is variable. Given the degree of irreproducibility that exists among well-trained pathologists, realistic performance expectations should guide use of their interpretations.

The elevated 10-year risk of cervical precancer and cancer in women with human papillomavirus (HPV) type 16 or 18 and the possible utility of type-specific HPV testing in clinical practice

BACKGROUND

Human papillomavirus (HPV) types 16 and 18 cause 60%-70% of cervical cancer worldwide, and other HPV types cause virtually all remaining cases. Pooled HPV testing for 13 oncogenic types, including HPV16 and 18, is currently used in clinical practice for triage of equivocal cytology and, in conjunction with Pap tests, is an option for general screening among women 30 years of age and older. It is not clear to what extent individual identification of HPV16 or HPV18 as an adjunct to pooled oncogenic HPV testing might effectively identify women at particularly high risk of cervical cancer or its immediate precursor, cervical intraepithelial neoplasia 3 (CIN3).

METHODS

From April 1, 1989, to November 2, 1990, a total of 20 810 women in the Kaiser Permanente health plan in Portland, OR, enrolled in a cohort study of HPV and cervical neoplasia. Women were tested for 13 oncogenic HPV types by Hybrid Capture 2 (HC2), and those women with a positive HC2 test were tested for HPV16 and 18. Enrollment Pap smear interpretation and HPV test results were linked to histologically confirmed CIN3 and cervical cancer (> or = CIN3) occurring during 10 years of cytologic follow-up. We calculated cumulative incidence rates with 95% confidence intervals for each interval up to 122 months using Kaplan-Meier methods.

RESULTS

The 10-year cumulative incidence rates of > or = CIN3 were 17.2% (95% confidence interval [CI] = 11.5% to 22.9%) among HPV16+ women and 13.6% (95% CI = 3.6% to 23.7%) among HPV18+ (HPV16-) women, but only 3.0% (95% CI = 1.9% to 4.2%) among HC2+ women negative for HPV16 or HPV18. The 10-year cumulative incidence among HC2- women was 0.8% (95% CI = 0.6% to 1.1%). A subanalysis among women 30 years of age and older with normal cytology at enrollment strengthened the observed risk differences.

CONCLUSIONS

HPV screening that distinguishes HPV16 and HPV18 from other oncogenic HPV types may identify women at the greatest risk of > or = CIN3 and may permit less aggressive management of other women with oncogenic HPV infections.

Comparison of three management strategies for patients with atypical squamous cells of undetermined significance: baseline results from a randomized trial

BACKGROUND

More than 2 million U.S. women receive an equivocal cervical cytologic diagnosis (atypical squamous cells of undetermined significance [ASCUS]) each year. Effective colposcopy triage strategies are needed to identify the minority of women who have clinically significant disease while avoiding excessive follow-up evaluation for others.

METHODS

The ASCUS/LSIL (i.e., low-grade squamous intraepithelial lesion) Triage Study (ALTS) is a multicenter, randomized trial comparing the sensitivity and specificity of the following three management strategies to detect cervical intraepithelial neoplasia grade 3 (CIN3): 1) immediate colposcopy (considered to be the reference standard), 2) triage to colposcopy based on human papillomavirus (HPV) results from Hybrid Capture 2(TM) (HC 2) and thin-layer cytology results, or 3) triage based on cytology results alone. This article summarizes the cross-sectional enrollment results for 3488 women with a referral diagnosis of ASCUS. All statistical tests are two-sided.

RESULTS

Among participants with ASCUS, the underlying prevalence of histologically confirmed CIN3 was 5.1%. Sensitivity to detect CIN3 or above by testing for cancer-associated HPV DNA was 96.3% (95% confidence interval [CI] = 91.6% to 98.8%), with 56.1% of women referred to colposcopy. Sensitivity of a single repeat cytology specimen with a triage threshold of HSIL or above was 44.1% (95% CI = 35.6% to 52.9%), with 6.9% referred. Sensitivity of a lower cytology triage threshold of ASCUS or above was 85.3% (95% CI = 78.2% to 90.8%), with 58.6% referred.

CONCLUSIONS

HC 2 testing for cancer-associated HPV DNA is a viable option in the management of women with ASCUS. It has greater sensitivity to detect CIN3 or above and specificity comparable to a single additional cytologic test indicating ASCUS or above.

Carcinogenic human papillomavirus infection

Infections with human papillomavirus (HPV) are common and transmitted by direct contact. Although the great majority of infections resolve within 2 years, 13 phylogenetically related, sexually transmitted HPV genotypes, notably HPV16, cause - if not controlled immunologically or by screening - virtually all cervical cancers worldwide, a large fraction of other anogenital cancers and an increasing proportion of oropharyngeal cancers. The carcinogenicity of these HPV types results primarily from the activity of the oncoproteins E6 and E7, which impair growth regulatory pathways. Persistent high-risk HPVs can transition from a productive (virion-producing) to an abortive or transforming infection, after which cancer can result after typically slow accumulation of host genetic mutations. However, which precancerous lesions progress and which do not is unclear; the majority of screening-detected precancers are treated, leading to overtreatment. The discovery of HPV as a carcinogen led to the development of effective preventive vaccines and sensitive HPV DNA and RNA tests. Together, vaccination programmes (the ultimate long-term preventive strategy) and screening using HPV tests could dramatically alter the landscape of HPV-related cancers. HPV testing will probably replace cytology-based cervical screening owing to greater reassurance when the test is negative. However, the effective implementation of HPV vaccination and screening globally remains a challenge.

Epidemiology and natural history of human papillomavirus infections and type-specific implications in cervical neoplasia

Worldwide human papillomavirus (HPV) prevalence in women with normal cytology at any given point in time is approximately 10% indicating that HPV is one of the most common sexually transmitted infections. HPV-16 is consistently the most common type and HPV-18 the second with some minor regional differences. Furthermore, across the spectrum of cervical lesions, HPV-16 is consistently the most common HPV type contributing to 50-55% of invasive cervical cancer cases strongly suggesting that this viral type has a biological advantage for transmission, persistency and transformation. The same phenomenon is observed albeit at a lower level for HPV-18 and HPV-45. Sexual behavioral patterns across age groups and populations are central to the description of the HPV circulation and of the risk of infection. The concept of group sexual behavior (in addition to individual sexual behavior) is important in exploring HPV transmission and has implications for defining and monitoring HPV and cancer prevention strategies. In natural history studies, the pattern of HPV DNA prevalence by age groups is similar to the patterns of HPV incidence. Rates of exposure in young women are high and often include multiple types. There is a spontaneous and rapid decrease of the HPV DNA detection rates in the middle-age groups followed by a second rise in the post-menopausal years. This article reviews: 1) the evidence in relation to the burden of HPV infections in the world and the contributions of each HPV type to the spectrum of cervical cellular changes spanning from normal cytology to invasive cervical cancer; 2) the critical role of the patterns of sexual behavior in the populations; and 3) selected aspects of the technical and methodological complexity of natural history studies of HPV and cervical neoplasia.

American Cancer Society, American Society for Colposcopy and Cervical Pathology, and American Society for Clinical Pathology screening guidelines for the prevention and early detection of cervical cancer

An update to the American Cancer Society (ACS) guideline regarding screening for the early detection of cervical precancerous lesions and cancer is presented. The guidelines are based on a systematic evidence review, contributions from 6 working groups, and a recent symposium cosponsored by the ACS, the American Society for Colposcopy and Cervical Pathology, and the American Society for Clinical Pathology, which was attended by 25 organizations. The new screening recommendations address age-appropriate screening strategies, including the use of cytology and high-risk human papillomavirus (HPV) testing, follow-up (eg, the management of screen positives and screening intervals for screen negatives) of women after screening, the age at which to exit screening, future considerations regarding HPV testing alone as a primary screening approach, and screening strategies for women vaccinated against HPV16 and HPV18 infections.

Human papillomavirus testing in the prevention of cervical cancer

Strong evidence now supports the adoption of cervical cancer prevention strategies that explicitly focus on persistent infection with the causal agent, human papillomavirus (HPV). To inform an evidence-based transition to a new public health approach for cervical cancer screening, we summarize the natural history and cervical carcinogenicity of HPV and discuss the promise and uncertainties of currently available screening methods. New HPV infections acquired at any age are virtually always benign, but persistent infections with one of approximately 12 carcinogenic HPV types explain virtually all cases of cervical cancer. In the absence of an overtly persistent HPV infection, the risk of cervical cancer is extremely low. Thus, HPV test results predict the risk of cervical cancer and its precursors (cervical intraepithelial neoplasia grade 3) better and longer than cytological or colposcopic abnormalities, which are signs of HPV infection. The logical and inevitable move to HPV-based cervical cancer prevention strategies will require longer screening intervals that will disrupt current gynecologic and cytology laboratory practices built on frequent screening. A major challenge will be implementing programs that do not overtreat HPV-positive women who do not have obvious long-term persistence of HPV or treatable lesions at the time of initial evaluation. The greatest potential for reduction in cervical cancer rates from HPV screening is in low-resource regions that can implement infrequent rounds of low-cost HPV testing and treatment.

Population-based study of human papillomavirus infection and cervical neoplasia in rural Costa Rica

BACKGROUND

Human papillomavirus (HPV) is the main cause of cervical neoplasia. Because few population-based studies have investigated the prevalence of type-specific infection in relation to cervical disease, we studied a high-risk population, estimating the prevalence of HPV infection and the risk associated with various HPV types.

METHODS

We screened 9175 women in Guanacaste, Costa Rica, to obtain a referent standard final diagnosis, and tested 3024 women for more than 40 types of HPV with a polymerase chain reaction-based system.

RESULTS

Among women with normal cytology, HPV infections peaked first in women younger than 25 years, and they peaked again at age 55 years or older with predominantly non-cancer-associated types of HPV and uncharacterized HPV types. Low-grade squamous intraepithelial lesions (LSILs) (n = 189) decreased consistently with age. The prevalence of high-grade squamous intraepithelial lesions (HSILs) (n = 128) peaked first around age 30 years and again at age 65 years or older. Seventy-three percent of LSILs were HPV positive, with HPV16 being the predominant type (16% of positive subjects). HPV was found in 89% of HSILs and 88% of cancers, with HPV16 being strongly predominant (51% and 53% of positive subjects). Virtually all HSILs and cancers had cancer-associated HPV types, with high odds ratios (ORs) and attributable fractions around 80%. Risk for HPV16 was particularly high (OR for HSILs = 320, 95% confidence interval [CI] = 97-1000; OR for cancer = 710, 95% CI = 110-4500).

CONCLUSIONS

We confirm the early decline of HPV infection with age but note increased prevalence after menopause, which could be related to a second peak of HSILs, an observation that warrants further investigation. At least 80% of HPVs involved in cervical carcinogenesis in this population have been characterized. Polyvalent vaccines including the main cancer-associated HPV types may be able to prevent most cases of cervical disease in this region.

Cervical cancer risk for women undergoing concurrent testing for human papillomavirus and cervical cytology: a population-based study in routine clinical practice

BACKGROUND

Concurrent testing for human papillomavirus (HPV) and cervical cytology (co-testing) is an approved alternative to cytology alone in women aged 30 years and older. We aimed to assess the safety in routine clinical practice of 3-year screening intervals for women testing negative for HPV with normal cytology and to assess if co-testing can identify women at high risk of cervical cancer or cervical intraepithelial neoplasia grade 3 (CIN3) or worse over 5 years.

METHODS

We assessed the 5-year cumulative incidence, starting in 2003-05, of cervical cancer and CIN3 or worse for 331,818 women aged 30 years and older who enrolled in co-testing at Kaiser Permanente Northern California (Berkeley, CA, USA) and had adequate enrolment co-test results. Follow-up continued until Dec 31, 2009. We defined cumulative incidence to include prevalence at enrolment and incidence after enrolment. Prevalence at enrolment was defined as the ratio of women diagnosed with each outcome on the biopsy visit immediately after their enrolment screening visit to the total enrolled women. At screening visits only HPV test and Pap smear samples were collected, and at biopsy visits colposcopically directed biopsies were taken. To estimate post-enrolment incidence, we used Weibull survival models.

FINDINGS

In 315,061 women negative by HPV testing, the 5-year cumulative incidence of cancer was 3.8 per 100,000 women per year, slightly higher than for the 306,969 who were both negative by HPV and Pap testing (3.2 per 100,000), and half the cancer risk of the 319,177 who were negative by Pap testing (7.5 per 100,000). 313,465 (99.5%) women negative by HPV testing had either normal cytology or equivocal abnormalities. Abnormal cytology greatly increased cumulative incidence of CIN3 or worse over 5 years for the 16,757 positive by HPV testing (12.1%vs 5.9%; p<0.0001). By contrast, although statistically significant, abnormal cytology did not increase 5-year risk of CIN3 or worse for women negative by HPV testing to a substantial level (0.86%vs 0.16%; p=0.004). 12,208 (73%) of the women positive by HPV testing had no cytological abnormality, and these women had 258 (35%) of 747 CIN3 or adenocarcinoma in situ, [corrected] 25 (29%) of 87 cancers, and 17 (63%) of 27 adenocarcinomas.

INTERPRETATION

For women aged 30 years and older in routine clinical practice who are negative by co-testing (both HPV and cytology), 3-year screening intervals were safe because a single negative test for HPV was sufficient to reassure against cervical cancer over 5 years. Incorporating HPV testing with cytology also resulted in earlier identification of women at high risk of cervical cancer, especially adenocarcinoma. Testing for HPV without adjunctive cytology might be sufficiently sensitive for primary screening for cervical cancer.

FUNDING

Intramural Research Program of the US National Cancer Institute/NIH/DHHS, and the American Cancer Society.

Rapid clearance of human papillomavirus and implications for clinical focus on persistent infections

Health professionals and the public need to understand the natural history of human papillomavirus (HPV) infections of the cervix to best use the information provided by new molecular screening tests. We investigated outcomes of 800 carcinogenic HPV infections detected in 599 women at enrollment into a population-based cohort (Guanacaste, Costa Rica). For individual infections, we calculated cumulative proportions of three outcomes (viral clearance, persistence without cervical intraepithelial neoplasia grade 2 or worse [CIN2+], or persistence with new diagnosis of CIN2+) at successive 6-month time points for the first 30 months of follow-up. Cervical specimens were tested for carcinogenic HPV genotypes using an L1 degenerate-primer polymerase chain reaction method. Infections typically cleared rapidly, with 67% (95% confidence interval [CI] = 63% to 70%) clearing by 12 months. However, among infections that persisted at least 12 months, the risk of CIN2+ diagnosis by 30 months was 21% (95% CI = 15% to 28%). The risk of CIN2+ diagnosis was highest among women younger than 30 years with HPV-16 infections that persisted for at least 12 months (53%; 95% CI = 29% to 76%). These findings suggest that the medical community should emphasize persistence of cervical HPV infection, not single-time detection of HPV, in management strategies and health messages.

The carcinogenicity of human papillomavirus types reflects viral evolution

Persistent infections with carcinogenic human papillomaviruses (HPV) cause virtually all cervical cancers. Cervical HPV types (n > 40) also represent the most common sexually transmitted agents, and most infections clear in 1-2 years. The risks of persistence and neoplastic progression to cancer and its histologic precursor, cervical intraepithelial neoplasia grade 3 (CIN3), differ markedly by HPV type. To study type-specific HPV natural history, we conducted a 10,000-woman, population-based prospective study of HPV infections and CIN3/cancer in Guanacaste, Costa Rica. By studying large numbers of women, we wished to separate viral persistence from neoplastic progression. We observed a strong concordance of newly-revised HPV evolutionary groupings with the separate risks of persistence and progression to CIN3/cancer. HPV16 was uniquely likely both to persist and to cause neoplastic progression when it persisted, making it a remarkably powerful human carcinogen that merits separate clinical consideration. Specifically, 19.9% of HPV16-infected women were diagnosed with CIN3/cancer at enrollment or during the five-year follow-up. Other carcinogenic types, many related to HPV16, were not particularly persistent but could cause neoplastic progression, at lower rates than HPV16, if they did persist. Some low-risk types were persistent but, nevertheless, virtually never caused CIN3. Therefore, carcinogenicity is not strictly a function of persistence. Separately, we noted that the carcinogenic HPV types code for an E5 protein, whereas most low-risk types either lack a definable homologous E5 ORF and/or a translation start codon for E5. These results present several clear clues and research directions in our ongoing efforts to understand HPV carcinogenesis.

HPV DNA testing in cervical cancer screening: results from women in a high-risk province of Costa Rica

CONTEXT

Human papillomaviruses (HPVs) are known to cause most cervical cancer worldwide, but the utility of HPV DNA testing in cervical cancer prevention has not been determined.

OBJECTIVE

To provide comprehensive data on the screening performance of HPV testing for the most common carcinogenic types, at different levels of analytic sensitivity.

DESIGN

Laboratory analysis conducted during 1993-1995, using 3 cytologic techniques and cervicography, followed by colposcopic examination of women with any abnormal cervical finding, to detect all high-grade intraepithelial lesions and cancer (reference standard of clinically significant disease). The HPV testing was performed subsequently with masking regarding clinical findings.

SETTING

Guanacaste Province, Costa Rica, a region with a high age-adjusted incidence of cervical cancer.

PARTICIPANTS

Of 11742 randomly selected women, 8554 nonpregnant, sexually active women without hysterectomies underwent initial HPV DNA testing using the original Hybrid Capture Tube test; a stratified subsample of 1119 specimens was retested using the more analytically sensitive second generation assay, the Hybrid Capture II test.

MAIN OUTCOME MEASURES

Receiver operating characteristic analysis of detection of cervical high-grade intraepithelial lesions and cancer by HPV DNA testing based on different cut points of positivity.

RESULTS

An analytic sensitivity of 1.0 pg/mL using the second generation assay would have permitted detection of 88.4% of 138 high-grade lesions and cancers (all 12 cancers were HPV-positive), with colposcopic referral of 12.3% of women. Papanicolaou testing using atypical squamous cells of undetermined significance as a cut point for referral resulted in 77.7% sensitivity and 94.2% specificity, with 6.9% referred. Specificity of the second generation assay for positivity for high-grade lesions and cancer was 89.0%, with 33.8% of remaining HPV DNA-positive subjects having low-grade or equivocal microscopically evident lesions. The higher detection threshold of 10 pg/mL used with the original assay had a sensitivity of 74.8% and a specificity of 93.4%. Lower levels of detection with the second generation assay (<1 pg/mL) proved clinically nonspecific without gains in diagnostic sensitivity.

CONCLUSIONS

In this study population, a cut point of 1.0 pg/mL using the second generation assay permitted sensitive detection of cervical high-grade lesions and cancer, yielding an apparently optimal trade-off between high sensitivity and reasonable specificity for this test. The test will perform best in settings in which sensitive detection of high-grade lesions and cancer is paramount. Because HPV prevalence varies by population, HPV testing positive predictive value for detection of high-grade lesions and cancer will vary accordingly, with implications for utility relative to other cervical cancer screening methods.

Classification of weakly carcinogenic human papillomavirus types: addressing the limits of epidemiology at the borderline

Virtually all cases of cervical cancer are caused by persistent infections with a restricted set of human papillomaviruses (HPV). Some HPV types, like HPV16 and HPV18, are clear and powerful carcinogens. However, the categorization of the most weakly carcinogenic HPV types is extremely challenging. The decisions are important for screening test and vaccine development. This article describes for open discussion an approach recently taken by a World Health Organization International Agency for Research on Cancer (IARC) Monographs Working Group to re-assess the carcinogenicity of different HPV types.

Reduced prevalence of oral human papillomavirus (HPV) 4 years after bivalent HPV vaccination in a randomized clinical trial in Costa Rica

Background

Human papillomavirus (HPV) infection, particularly with type 16, causes a growing fraction of oropharyngeal cancers, whose incidence is increasing, mainly in developed countries. In a double-blind controlled trial conducted to investigate vaccine efficacy (VE) of the bivalent HPV 16/18 vaccine against cervical infections and lesions, we estimated VE against prevalent oral HPV infections 4 years after vaccination.

Methods and Findings

A total of 7,466 women 18–25 years old were randomized (1∶1) to receive the HPV16/18 vaccine or hepatitis A vaccine as control. At the final blinded 4-year study visit, 5,840 participants provided oral specimens (91·9% of eligible women) to evaluate VE against oral infections. Our primary analysis evaluated prevalent oral HPV infection among all vaccinated women with oral and cervical HPV results. Corresponding VE against prevalent cervical HPV16/18 infection was calculated for comparison. Oral prevalence of identifiable mucosal HPV was relatively low (1·7%). Approximately four years after vaccination, there were 15 prevalent HPV16/18 infections in the control group and one in the vaccine group, for an estimated VE of 93·3% (95% CI = 63% to 100%). Corresponding efficacy against prevalent cervical HPV16/18 infection for the same cohort at the same visit was 72·0% (95% CI = 63% to 79%) (p versus oral VE = 0·04). There was no statistically significant protection against other oral HPV infections, though power was limited for these analyses.

Conclusions

HPV prevalence four years after vaccination with the ASO4-adjuvanted HPV16/18 vaccine was much lower among women in the vaccine arm compared to the control arm, suggesting that the vaccine affords strong protection against oral HPV16/18 infection, with potentially important implications for prevention of increasingly common HPV-associated oropharyngeal cancer.

ClinicalTrials.gov, Registry number NCT00128661

Interim guidance for the use of human papillomavirus DNA testing as an adjunct to cervical cytology for screening

Human papillomavirus (HPV) DNA testing was recently approved by the Food and Drug Administration for use as an adjunct to cytology for cervical cancer screening. To help provide guidance to clinicians and patients when using HPV DNA testing as an adjunct to cervical cytology for screening, a workshop was cosponsored by the National Institutes of Health-National Cancer Institute, American Society of Colposcopy and Cervical Pathology (ASCCP), and American Cancer Society. Consensus was reached based on a literature review, expert opinion, and unpublished results from large ongoing screening studies. The conclusions of the workshop were that HPV DNA testing may be added to cervical cytology for screening in women aged 30 years or more. Women whose results are negative by both HPV DNA testing and cytology should not be rescreened before 3 years. Women whose results are negative by cytology, but are high-risk HPV DNA positive, are at a relatively low risk of having high-grade cervical neoplasia, and colposcopy should not be performed routinely in this setting. Instead, HPV DNA testing along with cervical cytology should be repeated in these women at 6 to 12 months. If test results of either are abnormal, colposcopy should then be performed. This guidance should assist clinicians in utilizing HPV DNA testing in an effective manner, while minimizing unnecessary evaluations and treatments.

Chapter 2: Natural history of anogenital human papillomavirus infection and neoplasia

This chapter suggests promising areas of future epidemiologic research on human papillomavirus (HPV) and anogenital cancer, organized around our understanding of cervical carcinogenesis. The major steps in cervical carcinogenesis include HPV infection, HPV persistence over a certain period of time, progression to precancer, and invasion. Backward steps include clearance of HPV infection and regression of precancer. Additional studies of incident HPV infections among virgins initiating sexual activity could clarify the earliest aspects of transmission and immune response. Research on older women and their male partners should focus on understanding the determinants of varying age-specific HPV prevalence curves and underlying dynamics of viral persistence, clearance, and latency. It will be particularly important for epidemiologists to define HPV persistence rigorously in order to guide clinical management and vaccine trials. Intensive longitudinal studies that collect visual, microscopic (cytologic and histologic), and molecular data will be needed to understand the fate of individual HPV infections and to clarify whether multiple, concurrent infections act independently on the cervix. Case-control designs will be useful mainly in searching for new biomarkers of risk of progression among HPV-infected women that could then be validated prospectively. Prospective confirmation is also needed for the etiologic cofactors established by case-control studies of invasive cervical cancer. Much of the knowledge about cervical cancer might apply to anal neoplasia. Epidemiologic studies of other genital tumors such as penile neoplasia are still needed, but multicentric groups must place great emphasis on measurement technology, given the difficulty in obtaining reliable comprehensive measurements.

A 2‐Year Prospective Study of Human Papillomavirus Persistence among Women with a Cytological Diagnosis of Atypical Squamous Cells of Undetermined Significance or Low‐Grade Squamous Intraepithelial Lesion

BACKGROUND

Cervical cancer is caused by persistent infection with human papillomavirus (HPV). Most infections and associated lesions clear spontaneously. It is important to define the determinants and timing of clearance, so that viral persistence can be recognized and managed.

METHODS

We investigated HPV natural history among 4504 subjects from ALTS (Atypical Squamous Cells of Undetermined Significance/Low-Grade Squamous Intraepithelial Lesions Triage Study). A discrete-time Markov model was used to simultaneously describe the prevalence, incidence, and persistence of type-specific HPV infection over 24 months in women with equivocal or mildly abnormal cytological results. Interactions between multiple HPV types infecting the same woman were examined for incidence of new infection (after an HPV-16 infection) and persistence of a current infection within groups defined by phylogenetic relatedness or by carcinogenicity.

RESULTS

Ninety-one percent (95% credible interval [CI], 90%-92%) of prevalent HPV infections at enrollment cleared within 24 months. The probability that an infection would persist for a further 6 months increased with the duration of infection, from 37% (95% CI, 35%-39%) for a newly observed infection to 65% (95% CI, 61%-70%) for an infection that had already persisted for > or =18 months. No consistent evidence of interactions was found between multiple HPV types regarding the incidence of new infection after an HPV-16 infection or regarding persistence of current HPV infection.

CONCLUSION

Although virtually all HPV infections clear within 2 years, the remaining infections have a high potential for persistence and, by implication, progression to precancer and cancer. Once biological and behavioral determinants are controlled for, HPV infections with different types seem to be independent of each other.

Baseline cytology, human papillomavirus testing, and risk for cervical neoplasia: a 10-year cohort analysis

BACKGROUND

Annual Pap smear screening has been favored over less frequent screening in the United States to minimize the risk of cervical cancer. We evaluated whether simultaneous screening with a Pap test and human papillomavirus (HPV) testing is useful for assessing the risk for cervical intraepithelial neoplasia (CIN) 3 or cervical cancer.

METHODS

We enrolled 23 702 subjects in a study of HPV infection at Kaiser Permanente, Northwest Division, Portland, OR. Data were analyzed for 20 810 volunteers who were at least 16 years old (mean = 35.9 years) with satisfactory baseline Pap tests and suitable samples for HPV testing. Women were followed for up to 122 months (from April 1, 1989, to June 30, 1999) to determine the risk for histopathologically confirmed CIN3 or cancer.

RESULTS

Among 171 women with CIN3 or cancer diagnosed over 122 months, 123 (71.9%, 95% confidence interval [CI] = 65.2% to 78.7%) had baseline Pap results of atypical squamous cells or worse and/or a positive HPV test, including 102 (86.4%, 95% CI = 80.3% to 92.6%) of the 118 cases diagnosed within the first 45 months of follow-up. During this 45-month period, the cumulative incidence of CIN3 or cancer was 4.54% (95% CI = 3.61% to 5.46%) among women with a Pap test result of atypical squamous cells or worse, positive HPV tests, or both compared with 0.16% (95% CI = 0.08% to 0.24%) among women with negative Pap and HPV tests. Age, screening behavior, a history of cervical cancer precursors, and a history of treatment for CIN minimally affected results.

CONCLUSIONS

Negative baseline Pap and HPV tests were associated with a low risk for CIN3 or cancer in the subsequent 45 months, largely because a negative HPV test was associated with a decreased risk of cervical neoplasia. Negative combined test results should provide added reassurance for lengthening the screening interval among low-risk women, whereas positive results identify a relatively small subgroup that requires more frequent surveillance.

Longitudinal study of human papillomavirus persistence and cervical intraepithelial neoplasia grade 2/3: critical role of duration of infection

BACKGROUND

The natural history of human papillomavirus (HPV) infections in older women is critical for preventive strategies, including vaccination and screening intervals, but is poorly understood. In a 7-year population-based cohort study in Guanacaste, Costa Rica, we examined whether women's age and the duration of carcinogenic HPV infections influenced subsequent persistence of infection and risk of cervical intraepithelial neoplasia grade 2 (CIN 2) or worse disease.

METHODS

At enrollment, of the 9466 participants eligible for pelvic examination, 9175 were screened for cervical neoplasia using multiple methods; those with CIN 2 or worse disease were censored and treated. Participants at low risk of CIN 2 or worse (n = 6029) were rescreened at 5-7 years (passively followed), whereas higher-risk participants (n = 2115) and subsets of low-risk women (n = 540) and initially sexually inactive women (n = 410) were rescreened annually or semiannually (actively followed) for up to 7 years. HPV testing was done using a polymerase chain reaction-based method. We determined, by four age groups (18-25, 26-33, 34-41, and > or =42 years), the proportion of prevalent infections (found at baseline) and newly detected infections (first found during follow-up) that persisted at successive 1-year time points and calculated absolute risks of CIN 2 and CIN grade 3 (CIN 3) or worse during follow-up. P values are two-sided.

RESULTS

Regardless of the woman's age, newly detected infections were associated with very low absolute risks of persistence, CIN 2, or worse disease. For newly detected infections, the rate of progression to CIN 2+ (or CIN 3+), after 3 years of follow-up, was not higher for women aged 34 years and older than for younger women. Moreover, rates of newly detected infections declined sharply with age (in the actively followed group, at ages 18-25, 26-33, 34-41, and > or =42 years, rates were 35.9%, 30.6%, 18.1%, and 13.5%, respectively; P < .001). Among prevalent infections, persistent infections among older women (> or =42 years) was higher than that among younger age groups or new infections at any age (P < .01 for comparison of eight groups). Most (66 of 85) CIN 2 or worse detected during follow-up was associated with prevalent infections. Only a small subset (25 of 1128) of prevalent infections persisted throughout follow-up without apparent CIN 2 or worse.

CONCLUSIONS

The rate of new infections declines with age, and new infections typically do not progress to CIN 2 or worse disease in older women; thus, overall potential benefit of prophylactic vaccination or frequent HPV screening to prevent or detect new carcinogenic HPV infections at older ages is low.

A prospective study of age trends in cervical human papillomavirus acquisition and persistence in Guanacaste, Costa Rica

BACKGROUND

Cross-sectional human papillomavirus (HPV) DNA prevalence peaks at young ages, reflecting sexual acquisition and typically rapid clearance. In some populations, HPV prevalence demonstrates a second peak in older women. Longitudinal data may help to explain this second peak.

METHODS

We followed a population-based cohort of 7237 women in Guanacaste, Costa Rica, in which we had previously observed a second peak in the baseline HPV prevalence in older women. We tested for >40 HPV types by polymerase chain reaction. We analyzed age-specific patterns of acquisition and persistence 5-7 years after enrollment for individual HPV types.

RESULTS

At enrollment and follow-up, cross-sectional data revealed U-shaped age-specific HPV prevalence curves for virtually every type, with higher prevalences in the younger and older women than in the middle-aged women. Prospectively, acquisition of types decreased significantly as women aged (PTrend<.05, for both), with the highest peak in young women and a secondary minor peak in older women. Type-specific persistence of HPV increased with age (PTrend<.0001). Overall, HPV acquisition predominated at younger ages, whereas persistent infections gradually became more prominent with age (PTrend<.0001).

CONCLUSIONS

Newly apparent infections decreased, whereas persistence increased, with age; this latter tendency supports the utility of HPV screening in older women.

Diabetes mellitus, other medical conditions and familial history of cancer as risk factors for pancreatic cancer

In a population-based case-control study of pancreatic cancer conducted in three areas of the USA, 484 cases and 2099 controls were interviewed to evaluate the aetiologic role of several medical conditions/interventions, including diabetes mellitus, cholecystectomy, ulcer/gastrectomy and allergic states. We also evaluated risk associated with family history of cancer. Our findings support previous studies indicating that diabetes is a risk factor for pancreatic cancer, as well as a possible complication of the tumour. A significant positive trend in risk with increasing years prior to diagnosis of pancreatic cancer was apparent (P-value for test of trend = 0.016), with diabetics diagnosed at least 10 years prior to diagnosis having a significant 50% increased risk. Those treated with insulin had risks similar to those not treated with insulin (odds ratio (OR) = 1.6 and 1.5 respectively), and no trend in risk was associated with increasing duration of insulin treatment. Cholecystectomy also appeared to be a risk factor, as well as a consequence of the malignancy. Subjects with a cholecystectomy at least 20 years prior to the diagnosis of pancreatic cancer experienced a 70% increased risk, which was marginally significant. In contrast, subjects with a history of duodenal or gastric ulcer had little or no elevated risk (OR = 1.2; confidence interval = 0.9-1.6). Those treated by gastrectomy had the same risk as those not receiving surgery, providing little support for the hypothesis that gastrectomy is a risk factor for pancreatic cancer. A significant 40% reduced risk was associated with hay fever, a non-significant 50% decreased risk with allergies to animals, and a non-significant 40% reduced risk with allergies to dust/moulds. These associations, however, may be due to chance since no risk reductions were apparent for asthma or several other types of allergies. In addition, we observed significantly increased risks for subjects reporting a first-degree relative with cancers of the pancreas (OR = 3.2), colon (OR = 1.7) or ovary (OR = 5.3) and non-significantly increased risks for cancers of the endometrium (OR = 1.5) or breast (OR = 1.3). The pattern is consistent with the familial predisposition reported for pancreatic cancer and with the array of tumours associated with hereditary non-polyposis colon cancer.