Evidence for single-dose protection by the bivalent HPV vaccine-Review of the Costa Rica HPV vaccine trial and future research studies

The Costa Rica Vaccine Trial (CVT), a phase III randomized clinical trial, provided the initial data that one dose of the HPV vaccine could provide durable protection against HPV infection. Although the study design was to administer all participants three doses of HPV or control vaccine, 20% of women did not receive the three-dose regimens, mostly due to involuntary reasons unrelated to vaccination. In 2011, we reported that a single dose of the bivalent HPV vaccine could be as efficacious as three doses of the vaccine using the endpoint of persistent HPV infection accumulated over the first four years of the trial; findings independently confirmed in the GSK-sponsored PATRICIA trial. Antibody levels after one dose, although lower than levels elicited by three doses, were 9-times higher than levels elicited by natural infection. Importantly, levels remained essentially constant over at least seven years, suggesting that the observed protection provided by a single dose might be durable. Much work has been done to assure these non-randomized findings are valid. Yet, the group of recipients who received one dose of the bivalent HPV vaccine in the CVT and PATRICIA trials was small and not randomly selected nor blinded to the number of doses received. The next phase of research is to conduct a formal randomized, controlled trial to evaluate the protection afforded by a single dose of HPV vaccine. Complementary studies are in progress to bridge our findings to other populations, and to further document the long-term durability of antibody response following a single dose.

Abstract 2202: Long term risk prediction of p16/Ki-67 dual stain in triage of HPV-positive women

Background: Human papillomavirus (HPV) testing has been approved as a primary strategy for cervical cancer screening, either alone or in combination with cytology (co-testing), based on its high sensitivity and long-term reassurance against cervical precancer following a negative test result. However, nearly twice as many women will screen positive for HPV compared with cytology-based screening. Thus, effective management of HPV-positive women requires triage markers to distinguish those at high-risk who should be referred to colposcopy from those with benign infections who can safely return to routine screening. p16/Ki-67 dual stain cytology has previously shown good risk stratification for triage of HPV-positive women; however, studies with follow-up extending beyond 3 years are lacking. We evaluated the long-term risk prediction of p16/Ki-67 for detection of cervical precancer (cervical intraepithelial neoplasia grade 3 or worse, CIN3+) in a large population of HPV-positive women. Methods: 1,588 HPV-positive women screened with HPV/cytology co-testing were enrolled in 2012 at Kaiser Permanente Northern California. p16/Ki-67 cytology was performed on residual Surepath material and slides were evaluated for p16/Ki-67 positivity. Cervical histology endpoints were ascertained from the clinical database with follow-up through 2017. We conducted a Kaplan Meier analysis to estimate risk of CIN3+ by p16/Ki-67 and cytology (atypical squamous cells of undetermined significance or worse, ASC-US+, versus normal cytology). Risks were compared to internal benchmarks for colposcopy referral and for a one year return interval. Results: In women testing p16/Ki-67 positive at baseline, the 2-year risk of CIN3+ was 14.3%, compared with 2.2% in p16/Ki-67-negative women. For ASC-US+, the risk was 12.6% and 2.9% for normal cytology. The 5-year risk of CIN3+ in p16/Ki-67-positive women was 21.6% and 5.0% in p16/Ki-67-negatives. The 5-year risk of ASC-US+ was 17.1% compared to 8.2% for normal cytology. Among p16/Ki-67-negatives, the risk remained below the colposcopy referral threshold for 5 years while in women with normal cytology, the colposcopy referral threshold was crossed after year 3. Conclusion: In the first study evaluating long-term risk stratification of p16/Ki-67 dual staining, p16/Ki-67- negativity provided strong reassurance against CIN3+ for at least five years. In contrast, the risk in women with normal cytology crossed the colposcopy referral threshold after three years. These data support use of p16/Ki-67 for triage of HPV-positive women with the possibility of extending surveillance intervals in p16/Ki-67-negative women.

Citation Format: Megan A. Clarke, Barbara Fetterman, Mark Schiffman, Philip E. Castle, Eric Stiemerling, Diane Tokugawa, Nancy Poitras, Walter Kinney, Thomas Lorey, Nicolas Wentzensen. Long term risk prediction of p16/Ki-67 dual stain in triage of HPV-positive women [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2202.

Abstract 3273: rkmh: A MinHash toolbox for analyzing HPV coinfections

Human papillomaviruses are common infections transmitted by direct physical contact. Two sexually transmitted types, HPV16 and HPV18, are responsible for almost 75% of cervical cancer cases worldwide; another 10 types of >200 known types are considered carcinogenic. Among the four HPV16 lineages (A, B, C, and D), 100-fold differences in odds ratios for adenocarcinoma are observed. It is therefore informative to distinguish between infection with HPV16 lineages, even though they differ by as little as 2% of their genome. We present a computational toolkit, rkmh, for characterizing viral coinfections. rkmh uses kmer matching strategies to rapidly determine the most similar type or lineage reference genome for a given read. The proportion of reads matching each reference genome can then be calculated and the ratios of the infecting viruses can be estimated. To assess the performance of rkmh we first simulated 100bp paired end Illumina read sets from the PAVE database of HPV reference genomes, then also evaluated performance on a real HPV16 sample sequenced on the Ion Torrent Proton platform (typical read length 250bp), and a set of 3,660 Oxford Nanopore minION reads generated from two HPV16 reference strains (typical read length over 6500bp). We demonstrate that rkmh can adequately classify HPV infections at the type and lineage level. We discuss further applications of the tool in metagenomics. rkmh is freely available at https://github.com/edawson/rkmh.

Citation Format: Eric T. Dawson, Sarah Wagner, David Roberson, Meredith Yeager, Joseph Boland, Erik Garrison, Mark Schiffman, Tina Raine-Bennet, Thomas Lorey, Phillip Castle, Stephen Chanock, Lisa Mirabello, Richard Durbin. rkmh: A MinHash toolbox for analyzing HPV coinfections [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3273.

Is It Time to Move Beyond Visual Inspection With Acetic Acid for Cervical Cancer Screening?

Newly emerging low-cost molecular assays and improved visual tests for cervical cancer screening call into question the role of visual inspection with acetic acid (VIA). VIA-based screening continues to offer a low-cost, single-visit approach for screening. However, VIA is highly rater-dependent and has problematic accuracy. RNA, DNA, and protein tests are now available. They offer greater accuracy and the option for self-sampling, but the testing kits are expensive. As these new options continue to improve, the time to move beyond VIA is fast approaching.

Challenges in risk estimation using routinely collected clinical data: The example of estimating cervical cancer risks from electronic health-records

Electronic health-records (EHR) are increasingly used by epidemiologists studying disease following surveillance testing to provide evidence for screening intervals and referral guidelines. Although cost-effective, undiagnosed prevalent disease and interval censoring (in which asymptomatic disease is only observed at the time of testing) raise substantial analytic issues when estimating risk that cannot be addressed using Kaplan-Meier methods. Based on our experience analysing EHR from cervical cancer screening, we previously proposed the logistic-Weibull model to address these issues. Here we demonstrate how the choice of statistical method can impact risk estimates. We use observed data on 41,067 women in the cervical cancer screening program at Kaiser Permanente Northern California, 2003-2013, as well as simulations to evaluate the ability of different methods (Kaplan-Meier, Turnbull, Weibull and logistic-Weibull) to accurately estimate risk within a screening program. Cumulative risk estimates from the statistical methods varied considerably, with the largest differences occurring for prevalent disease risk when baseline disease ascertainment was random but incomplete. Kaplan-Meier underestimated risk at earlier times and overestimated risk at later times in the presence of interval censoring or undiagnosed prevalent disease. Turnbull performed well, though was inefficient and not smooth. The logistic-Weibull model performed well, except when event times didn't follow a Weibull distribution. We have demonstrated that methods for right-censored data, such as Kaplan-Meier, result in biased estimates of disease risks when applied to interval-censored data, such as screening programs using EHR data. The logistic-Weibull model is attractive, but the model fit must be checked against Turnbull non-parametric risk estimates.

Low-cost HPV testing and the prevalence of cervical infection in asymptomatic populations in Guatemala

BACKGROUND

A low cost and accurate method for detecting high-risk (HR) human papillomavirus (HPV) is important to permit HPV testing for cervical cancer prevention. We used a commercially available HPV method (H13, Hybribio) which was documented to function accurately in a reduced volume of cervical specimen to determine the most prevalent HPV types and the distribution of HPV infections in over 1795 cancer-free women in Guatemala undergoing primary screening for cervical cancer by cytology.

METHODS

HR-HPV detection was attempted in cervical samples from 1795 cancer-free women receiving Pap smears using the Hybribio™ real-time PCR assay of 13 HR types. The test includes a globin gene internal control. HPV positive samples were sequenced to determine viral type. Age-specific prevalence of HPV was also assessed in the study population.

RESULTS

A total of 13% (226/1717) of women tested HPV+, with 78 samples (4.3%) failing to amplify the internal control. The highest prevalence was found in younger women (< 30 years, 22%) and older ones (≥60 years, 15%). The six most common HR-HPV types among the 148 HPV+ typed were HPV16 (22%), HPV18 (11%), HPV39 (11%), HPV58 (10%), HPV52 (8%), and HPV45 (8%).

CONCLUSIONS

In this sample of cancer free women in Guatemala, HPV16 was the most prevalent HR type in Guatemala and the age-specific prevalence curve peaked in younger ages. Women in the 30-59-year age groups had a prevalence of HR-HPV of 8%, however, larger studies to better describe the epidemiology of HPV in Guatemala are needed.

Adherence patterns to extended cervical screening intervals in women undergoing human papillomavirus (HPV) and cytology cotesting

Although guidelines have recommended extended interval cervical screening using concurrent human papillomavirus (HPV) and cytology ("cotesting") for over a decade, little is known about its adoption into routine care. Using longitudinal medical record data (2003-2015) from Kaiser Permanente Northern California (KPNC), which adopted triennial cotesting in 2003, we examined adherence to extended interval screening. We analyzed predictors of screening intervals among 491,588 women undergoing routine screening, categorizing interval length into early (<2.5years), adherent (2.5<3.5years), or late (3.5<6.0years). We also examined repeated early screening in a subgroup of 50,691 women. Predictors examined included: cohort year (defined by baseline cotest, 2003-2009), race/ethnicity, and baseline age. Compared to the 2003 cohort, women in the 2009 cohort were significantly less likely to screen early (aOR=0.22, 95% CI=0.21, 0.23) or late (aOR=0.47, 95% CI=0.45, 0.49). African American (AA) and Hispanic women were less adherent overall than Non-Hispanic White women, with increased early [(AA: aOR=1.21, 95%CI=1.17, 1.25) (Hispanic: aOR=1.08, 95%CI=1.06, 1.11)] and late screening [(AA: aOR=1.23, 95%CI=1.19, 1.27) (Hispanic: aOR=1.06, 95%CI=1.03, 1.08)]. Asian women were slightly more likely to screen early (aOR=1.03, 95%CI=1.01, 1.05), and less likely to screen late (aOR=0.92, 95% CI=0.90, 0.94). Women aged 60-64years were most likely to screen early for two consecutive intervals (aOR=2.09, 95%CI=1.91, 2.29). Our study found that widespread and rapid adoption of extended interval cervical cancer screening is possible, at least in this managed care setting. Further research examining multilevel drivers promoting or restricting extended interval screening across diverse healthcare settings is needed.

Classification and evolution of human papillomavirus genome variants: Alpha-5 (HPV26, 51, 69, 82), Alpha-6 (HPV30, 53, 56, 66), Alpha-11 (HPV34, 73), Alpha-13 (HPV54) and Alpha-3 (HPV61)

HPV variants from the same type can be classified into lineages and sublineages based on the complete genome differences and the phylogenetic topologies. We examined nucleotide variations of twelve HPV types within the species Alpha-5 (HPV26, 51, 69, 82), Alpha-6 (HPV30, 53, 56, 66), Alpha-11 (HPV34, 73), Alpha-13 (HPV54) and Alpha-3 (HPV61) by analyzing 1432 partial sequences and 181 complete genomes from multiple geographic populations. The inter-lineage and inter-sublineage mean differences of HPV variants ranged between 0.9-7.3% and 0.3-0.9%, respectively. The heterogeneity and phylogenies of HPV isolates indicate an independent evolutionary history for each type. The noncoding regions were the most variable regions whereas the capsid proteins were relatively conserved. Certain variant lineages and/or sublineages were geographically-associated. These data provide the basis to further classify HPV variants and should foster future studies on the evolution of HPV genomes and the associations of HPV variants with cancer risk.

The Intersection of HPV Epidemiology, Genomics and Mechanistic Studies of HPV-Mediated Carcinogenesis

Of the ~60 human papillomavirus (HPV) genotypes that infect the cervicovaginal epithelium, only 12–13 “high-risk” types are well-established as causing cervical cancer, with HPV16 accounting for over half of all cases worldwide. While HPV16 is the most important carcinogenic type, variants of HPV16 can differ in their carcinogenicity by 10-fold or more in epidemiologic studies. Strong genotype-phenotype associations embedded in the small 8-kb HPV16 genome motivate molecular studies to understand the underlying molecular mechanisms. Understanding the mechanisms of HPV genomic findings is complicated by the linkage of HPV genome variants. A panel of experts in various disciplines gathered on 21 November 2016 to discuss the interdisciplinary science of HPV oncogenesis. Here, we summarize the discussion of the complexity of the viral–host interaction and highlight important next steps for selected applied basic laboratory studies guided by epidemiological genomic findings.

Clinical Outcomes after Conservative Management of Cervical Intraepithelial Neoplasia Grade 2 (CIN2) in Women Ages 21-39 Years

Cervical intraepithelial neoplasia grade 2 (CIN2) frequently regresses, is typically slow-growing, and rarely progresses to cancer. Some women forgo immediate treatment, opting for conservative management (heightened surveillance with cytology and colposcopy), to minimize overtreatment and increased risk of obstetric complications; however, there are limited data examining clinical outcomes in these women. We performed a retrospective cohort analysis of younger women diagnosed with initially untreated CIN1/2, CIN2 and CIN2/3 lesions at Kaiser Permanente Northern California between 2003 and 2015. Clinical outcomes were categorized into five mutually exclusive hierarchical groups: cancer, treated, returned to routine screening, persistent high-grade lesion, or persistent low-grade lesion. Median follow-up for the 2,417 women was 48 months. Six women were diagnosed with cancer (0.2%), all with history of high-grade cytology, and none after a negative cotest. Thirty percent of women were treated, and only 20% returned to routine screening; 50% remained in continued intensive follow-up, of which 86% had either low-grade cytology/histology or high-risk human papillomavirus (HPV) positivity, but not necessarily persistence of a single HPV type. No cancers were detected after a single negative cotest in follow-up. Almost half of initially untreated women did not undergo treatment, but remained by protocol in colposcopy clinic for 2 or more years in the absence of persisting CIN2⁺ Their incomplete return to total negativity was possibly due to sequential new and unrelated low-grade abnormalities. The prolonged colposcopic surveillance currently required to return to routine screening in the absence of persisting CIN2⁺ might not be necessary after a negative cotest.Significance: Many younger women under conservative management following an initial CIN2 result remain in a clinical protocol of prolonged intensified surveillance without a subsequent diagnosis of CIN2 or more severe diagnoses. More research is needed to determine whether such prolonged management might be unnecessary following a negative cotest for those women with an initial CIN2 but otherwise only low-grade findings. Cancer Prev Res; 11(3); 165-70. ©2018 AACR.

Human Papillomavirus DNA Methylation as a Biomarker for Cervical Precancer: Consistency across 12 Genotypes and Potential Impact on Management of HPV-Positive Women

Purpose: Human papillomavirus (HPV) DNA methylation testing is a promising triage option for women testing HPV positive during cervical cancer screening. However, the extent to which methylation indicates precancer for all 12 carcinogenic HPV types has not been evaluated.Experimental Design: In this nested case-control study, we tested up to 30 cases of precancer [cervical intraepithelial neoplasia grade 3 (CIN3)/adenocarcinoma in situ (AIS)] and 30 normal controls for each carcinogenic type (single infections with 16/18/31/33/35/39/45/51/52/56/58/59). Next-generation bisulfite sequencing was performed on CpG sites within the L1 and L2 genes. We calculated differences in methylation, ORs, and AUC. Using a fixed sensitivity of 80%, we evaluated the specificity and the risk of CIN3/AIS for best performing CpG sites, and compared the performance of an explorative multi-type methylation assay with current triage strategies.Results: Methylation was positively associated with CIN3/AIS across all 12 types. AUCs for the top sites ranged from 0.71 (HPV51 and HPV56) to 0.86 (HPV18). A combined 12-type methylation assay had the highest Youden index (0.46), compared with cytology (0.31) and a 5-type methylation assay, including only previously described types (0.26). The 12-type methylation assay had higher sensitivity (80% vs. 76.6%) and lower test positivity compared with cytology (38.5% vs. 48.7%). The risk of CIN3/AIS was highest for methylation positives and lowest for cytology or HPV16/18 positives.Conclusions: HPV DNA methylation is a general phenomenon marking the transition from HPV infection to precancer for all 12 carcinogenic types. Development of a combined multitype methylation assay may serve as a triage test for HPV-positive women. Clin Cancer Res; 24(9); 2194-202. ©2018 AACR.

T cell receptor repertoire among women who cleared and failed to clear cervical human papillomavirus infection: An exploratory proof-of-principle study

BACKGROUND

It is unknown why a minority of women fail to clear human papillomavirus (HPV) and develop precancer/cancer. Differences in T-cell receptor (TCR) repertoires may identify HPV16-infected women at highest-risk for progression to cancer. We conducted a proof-of-principle study nested within the Guanacaste HPV Natural History Study to evaluate the utility of next-generation sequencing for interrogating the TCR repertoires among women who cleared and failed to clear cervical HPV16.

METHODS

TCR repertoires of women with HPV16-related intraepithelial neoplasia grade 3 or higher (CIN3+; n = 25) were compared to women who cleared an incident HPV16 infection without developing precancer/cancer (n = 25). TCR diversity (richness and evenness) and relative abundance (RA) of gene segment (V [n = 51], D [n = 2], J [n = 13]) usage was evaluated; receiver operating curve analysis assessed the ability to differentiate case-control status.

RESULTS

TCR repertoire richness was associated with CIN3+ status (P = 0.001). Relative abundance (RA) of V-gene segments was enriched for associations between cases and controls. A single V-gene (TRBV6-7) was significantly associated with CIN3+ status (RA = 0.11%, 0.16%, among cases and controls, respectively, Bonferroni P = 0.0008). The estimated area under the curve using richness and V-gene segment RA was 0.83 (95% confidence interval: 0.73-0.90).

CONCLUSIONS

Substantial differences in TCR repertoire among women with CIN3+ compared to women who cleared infection were observed.

IMPACT

This is the first study to use next-generation sequencing to investigate TCR repertoire in the context of HPV infection. These findings suggest that women with HPV16-associated cervical lesions have significantly different TCR repertoires from disease-free women who cleared HPV16 infection.

Epidemiologic Evidence That Excess Body Weight Increases Risk of Cervical Cancer by Decreased Detection of Precancer

Purpose Obesity has been inconsistently linked to increased cervical cancer incidence and mortality; however, the effect of obesity on cervical screening has not been explored. We investigated the hypothesis that increased body mass might decrease detection of cervical precancer and increase risk of cervical cancer even in women undergoing state-of-the-art screening. Methods We conducted a retrospective cohort study of 944,227 women age 30 to 64 years who underwent cytology and human papillomavirus DNA testing (ie, cotesting) at Kaiser Permanente Northern California (January 2003 to December 2015). Body mass index was categorized as normal/underweight (< 25 kg/m²), overweight (25 to < 30 kg/m²), or obese (≥ 30 kg/m²). We estimated 5-year cumulative risks of cervical precancer and cancer by category of body mass index using logistic Weibull survival models. Results We observed lower risk of cervical precancer (n = 4,489) and higher risk of cervical cancer (n = 490) with increasing body mass index. Specifically, obese women had the lowest 5-year risk of precancer (0.51%; 95% CI, 0.48% to 0.54% v 0.73%; 95% CI, 0.70% to 0.76% in normal/underweight women; P trend < .001). In contrast, obese women had the highest 5-year risk of cancer (0.083%; 95% CI, 0.072% to 0.096% v 0.056%; 95% CI, 0.048% to 0.066% in normal/underweight women; P trend < .001). Results were consistent in subgroups defined by age (30 to 49 v 50 to 64 years), human papillomavirus status (positive v negative), and histologic subtype (glandular v squamous). Approximately 20% of cervical cancers could be attributed to overweight or obesity in the women in our study who underwent routine cervical screening. Conclusion In this large, screened population, overweight and obese women had an increased risk of cervical cancer, likely because of underdiagnosis of cervical precancer. Improvements in equipment and/or technique to assure adequate sampling and visualization of women with elevated body mass might reduce cervical cancer incidence.

Effect of Several Negative Rounds of Human Papillomavirus and Cytology Co-testing on Safety Against Cervical Cancer: An Observational Cohort Study

BACKGROUND

Current U.S. cervical cancer screening and management guidelines do not consider previous screening history, because data on multiple-round human papillomavirus (HPV) and cytology "co-testing" have been unavailable.

OBJECTIVE

To measure cervical cancer risk in routine practice after successive negative screening co-tests at 3-year intervals.

DESIGN

Observational cohort study.

SETTING

Integrated health care system (Kaiser Permanente Northern California, Oakland, California).

PATIENTS

990 013 women who had 1 or more co-tests from 2003 to 2014.

MEASUREMENTS

3- and 5-year cumulative detection of (risk for) cervical intraepithelial neoplasia grade 3, adenocarcinoma in situ, and cervical cancer (≥CIN3) in women with different numbers of negative co-tests, overall and within subgroups defined by previous co-test results or baseline age.

RESULTS

Five-year ≥CIN3 risks decreased after each successive negative co-test screening round (0.098%, 0.052%, and 0.035%). Five-year ≥CIN3 risks for an HPV-negative co-test, regardless of the cytology result, nearly matched the performance (reassurance) of a negative co-test for each successive round of screening (0.114%, 0.061%, and 0.041%). By comparison, ≥CIN3 risks for the cytology-negative co-test, regardless of the HPV result, also decreased with each successive round, but 3-year risks were as high as 5-year risks after an HPV-negative co-test (0.199%, 0.065%, and 0.043%). No interval cervical cancer cases were diagnosed after the second negative co-test. Independently, ≥CIN3 risks decreased with age. Length of previous screening interval did not influence future ≥CIN3 risks.

LIMITATION

Interval-censored observational data.

CONCLUSION

After 1 or more negative cervical co-tests (or HPV tests), longer screening intervals (every 5 years or more) might be feasible and safe.

PRIMARY FUNDING SOURCE

National Cancer Institute Intramural Research Program.

Effective use of human papillomavirus testing for cervical cancer screening requires extended intervals to target persistent infections and precancerous lesions

Invited editorial for PM 17 348R2, a CDC survey regarding primary HPV testing.

Smoking and subsequent human papillomavirus infection: a mediation analysis

PURPOSE

Smoking is an established risk factor for a human papillomavirus (HPV) infection advancing to cervical precancer and cancer, but its role earlier in the natural history is less clear. Smoking is inversely associated with possessing HPV antibodies from a past infection suggesting that smoking may influence acquiring subsequent infections.

METHODS

In a cohort of 1976 U.S. women, we evaluate whether reduced antibodies to HPV-16 is a mechanism for smoking's role on acquiring a subsequent HPV-16 infection, through the analytic technique of causal mediation analysis. We posit a causal model and estimate two counterfactually defined effects: a smoking impaired antibody-mediated indirect effect and a nonmediated direct effect representing all other potential mechanisms of smoking.

RESULTS

Compared to never smokers, current smokers had increased odds of HPV-16 infection by the antibody-mediated indirect effect (odds ratio [OR] = 1.29; 95% confidence interval [CI]: 1.11, 1.73); the estimated direct effect was very imprecise (OR = 0.57; 95% CI, 0.26-1.13). We observed a stronger estimated indirect effect among women who smoked at least half a pack of cigarettes daily (OR = 1.61, 95% CI, 1.27-2.15) than among women who smoked less than that threshold (OR = 1.09; 95% CI, 0.94-1.44).

CONCLUSIONS

This is the first study to directly test the mechanism underlying smoking as an HPV cofactor. The results support current smoking as a risk factor earlier in the natural history of HPV and are consistent with the hypothesis that smoking increases the risk of a subsequent infection by reducing immunity.

Mixture models for undiagnosed prevalent disease and interval-censored incident disease: applications to a cohort assembled from electronic health records

For cost-effectiveness and efficiency, many large-scale general-purpose cohort studies are being assembled within large health-care providers who use electronic health records. Two key features of such data are that incident disease is interval-censored between irregular visits and there can be pre-existing (prevalent) disease. Because prevalent disease is not always immediately diagnosed, some disease diagnosed at later visits are actually undiagnosed prevalent disease. We consider prevalent disease as a point mass at time zero for clinical applications where there is no interest in time of prevalent disease onset. We demonstrate that the naive Kaplan-Meier cumulative risk estimator underestimates risks at early time points and overestimates later risks. We propose a general family of mixture models for undiagnosed prevalent disease and interval-censored incident disease that we call prevalence-incidence models. Parameters for parametric prevalence-incidence models, such as the logistic regression and Weibull survival (logistic-Weibull) model, are estimated by direct likelihood maximization or by EM algorithm. Non-parametric methods are proposed to calculate cumulative risks for cases without covariates. We compare naive Kaplan-Meier, logistic-Weibull, and non-parametric estimates of cumulative risk in the cervical cancer screening program at Kaiser Permanente Northern California. Kaplan-Meier provided poor estimates while the logistic-Weibull model was a close fit to the non-parametric. Our findings support our use of logistic-Weibull models to develop the risk estimates that underlie current US risk-based cervical cancer screening guidelines. Published 2017. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

HPV16 E7 Genetic Conservation Is Critical to Carcinogenesis

Although most cervical human papillomavirus type 16 (HPV16) infections become undetectable within 1-2 years, persistent HPV16 causes half of all cervical cancers. We used a novel HPV whole-genome sequencing technique to evaluate an exceptionally large collection of 5,570 HPV16-infected case-control samples to determine whether viral genetic variation influences risk of cervical precancer and cancer. We observed thousands of unique HPV16 genomes; very few women shared the identical HPV16 sequence, which should stimulate a careful re-evaluation of the clinical implications of HPV mutation rates, transmission, clearance, and persistence. In case-control analyses, HPV16 in the controls had significantly more amino acid changing variants throughout the genome. Strikingly, E7 was devoid of variants in precancers/cancers compared to higher levels in the controls; we confirmed this in cancers from around the world. Strict conservation of the 98 amino acids of E7, which disrupts Rb function, is critical for HPV16 carcinogenesis, presenting a highly specific target for etiologic and therapeutic research.

Why does cervical cancer occur in a state-of-the-art screening program?

BACKGROUND

The goal of cervical screening is to detect and treat precancers before some become cancer. We wanted to understand why, despite state-of-the-art methods, cervical cancers occured in relationship to programmatic performance at Kaiser Permanente Northern California (KPNC), where >1,000,000 women aged ≥30years have undergone cervical cancer screening by triennial HPV and cytology cotesting since 2003.

METHODS

We reviewed clinical histories preceding cervical cancer diagnoses to assign "causes" of cancer. We calculated surrogate measures of programmatic effectiveness (precancers/(precancers and cancers)) and diagnostic yield (precancers and cancers per 1000 cotests), overall and by age at cotest (30-39, 40-49, and ≥50years).

RESULTS

Cancer was rare and found mainly in a localized (treatable) stage. Of 623 cervical cancers with at least one preceding or concurrent cotest, 360 (57.8%) were judged to be prevalent (diagnosed at a localized stage within one year or regional/distant stage within two years of the first cotest). Non-compliance with recommended screening and management preceded 9.0% of all cancers. False-negative cotests/sampling errors (HPV and cytology negative), false-negative histologic diagnoses, and treatment failures preceded 11.2%, 9.0%, and 4.3%, respectively, of all cancers. There was significant heterogeneity in the causes of cancer by histologic category (p<0.001 for all; p=0.002 excluding prevalent cases). Programmatic effectiveness (95.3%) and diagnostic yield were greater for squamous cell versus adenocarcinoma histology (p<0.0001) and both decreased with older ages (ptrend<0.0001).

CONCLUSIONS

A state-of-the-art intensive screening program results in very few cervical cancers, most of which are detected early by screening. Screening may become less efficient at older ages.

Abstract 4249: Evidence of APOBEC3 editing in the HPV16 genome

Human papillomavirus (HPV) is a very common sexually transmitted infection, however only a small proportion of women progress to cervical precancer or cancer. HPV16 is the most carcinogenic type, causing more than half of the cervical cancer globally. The HPV16 genome is 7,906base-pairs coding for 8 genes (E6, E7, E1, E2, E4, E5, L2, L1) and one upstream regulatory region (URR). Within HPV16 there are 4 main lineages (A, B, C, D) that are strongly associated with disease risk.

Human APOBEC3A (hA3A) cytidine deaminases have been shown to have antiviral effects. The APOBEC mutational process results in a C to T base change at specific motifs (5’ [C/T]•C&gt;T•W 3’). Previous studies established that there was evidence of APOBEC3 editing on a small number of HPV16 samples. It’s unknown how these mutations are related to infection clearance or the long-term accumulation of genomic mutations that contribute to HPV-associated cancers.

We conducted detailed analyses to comprehensively evaluate APOBEC3 editing on HPV16 genomes using HPV16 whole-genome sequencing data from 3,215 HPV16-infected women in the NCI-HPV Persistence and Progression (PaP) cohort. Cases were defined as women with cervical precancer (CIN3, N = 1,093) or cancer (N = 109) and controls were women with no histologic evidence of precancer or cancer (&lt;CIN2, N = 1,107). HPV16 DNA was extracted from banked specimens and whole-genome sequenced using a high-throughput assay. We evaluated all rare variants, defined as having a minor allele frequency of &lt;1%, for matching an APOBEC3-associated variant. An APOBEC3-associated variant was defined as a variant having one of the eight possible motifs (5’ [C/T]•C&gt;T•W 3’) out of 96 potential motifs of 3 base-pairs. Using logistic regression, we compared the number of APOBEC3-associated variants in cases and controls, among HPV16 variant lineages, and among genome regions of the virus.

We discovered that there is evidence of APOBEC3 editing throughout the HPV16 genome. Specifically, we observed that women with precancer or cancer had less APOBEC3-associated variants compared to the controls (OR = 0.84, p-value = 0.06). We further showed that women with an HPV16 A lineage infection have more APOBEC3-associated variants compared to those with a non-A lineage infection (OR = 1.35, p-value = 0.02). After controlling for the number of APOBEC3 vulnerable loci, we observed that the L1 (OR = 0.23, p-value = 0.04) and E7 (OR = 0.29, p-value = 0.07) genes have less APOBEC3 footprints overall, and particularly in the cases compared to the controls in these regions, compared to the viral non-coding upstream regulatory region (URR).

Overall, we found that APOBEC3 is not affecting the HPV16 genome in a uniform way, and instead, it appears to be targeting specific regions which could suggest antiviral activity. Importantly, we determined that APOBEC3-associated variants are less prevalent in cases which could be related to disease progression in these individuals. Further evaluation is underway.

Citation Format: Yanzi Xiao, Bin Zhu, Meredith Yeager, Michael Cullen, Joseph Boland, Nicolas Wentzensen, Tina Raine-Bennett, Zigui Chen, Kai Yu, Qi Yang, Mia Steinberg, David Roberson, Sara Bass, Laurie Burdette, Thomas Lorey, Philip Castle, Robert Burk, Mark Schiffman, Lisa Mirabello. Evidence of APOBEC3 editing in the HPV16 genome [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4249. doi:10.1158/1538-7445.AM2017-4249

Abstract 5296: Evaluation of p16/Ki-67 dual stain, cytology, and HPV16/18 genotyping for triage of HPV-positive women in a large screening population

Objectives: Primary HPV testing has been approved in the United States. Screening intervals can be safely extended for HPV-negative women, but the challenge lies in discriminating transient HPV infections from precancers among HPV-positives. In a large study at Kaiser Permanente Northern California (KPNC), candidate strategies for triage of HPV-positive women are being evaluated, including cytology, p16/Ki-67 dual stain (DS, CINtec PLUS) and HPV16/18 genotyping (cobas).

Methods: Over 13,000 HPV-positive women participating in cervical cancer screening at KPNC were enrolled. The dual stain and HPV genotyping assays were implemented and conducted at KPNC. Baseline results for 7,124 women are available and detection of CIN3 is currently evaluated only in cytology-positive women.

Results: Among 7,124 HPV-positive women, 4,107 (57.7%) were cytology-positive (ASC-US+), 3,056 (42.9%) were DS-positive, and 1,406 (19.7%) were positive for HPV16 or HPV18. Among all 3,017 HPV-positive, cytology-negative women, 911 (30.2%) were DS- positive, and 508 (16.8%) were positive for HPV16 or HPV18. Of 315 CIN3 detected so far, 280 (88.9%) were DS-positive and 176 (55.9%) were positive for HPV16 or HPV18. Major triage strategies including cytology alone, DS alone, as well as combinations of cytology and genotyping, and DS and genotyping will be presented at the meeting.

Discussion: In one of the largest clinical implementation studies of triage strategies, we showed that primary HPV screening followed by DS can reduce colposcopy referral compared to HPV-cytology co-testing while achieving high sensitivity. Additional follow-up is underway to evaluate the programmatic performance of several major candidate strategies.

Citation Format: Nicolas A. Wentzensen, Barbara Fetterman, Renee Bremer, Philip Castle, Diane Tokugawa, Nancy Poitras, Elizabeth Hosfield, Thomas Lorey, Mark Schiffman, Walter Kinney. Evaluation of p16/Ki-67 dual stain, cytology, and HPV16/18 genotyping for triage of HPV-positive women in a large screening population [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5296. doi:10.1158/1538-7445.AM2017-5296