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1.  Prevalence of and Risk Factors for Oral Human Papillomavirus Among Young Women in Costa Rica 
The Journal of Infectious Diseases  2013;208(10):1643-1652.
Background. Little is known about the epidemiology of oral human papillomavirus (HPV) in Latin America.
Methods. Women (N = 5838) aged 22–29 in the control and vaccine arms of an HPV-16/18 vaccine trial in Costa Rica had oral, cervical, and anal specimens collected. Samples were tested for alpha mucosal HPV types (SPF10/LiPA25 version 1); a subset of oral samples (n = 500) was tested for cutaneous HPV types in the genera alpha, beta, gamma, mu, and nu.
Results. In the control arm (n = 2926), 1.9% of women had an oral alpha mucosal HPV detected, 1.3% had carcinogenic HPV, and 0.4% had HPV-16; similar patterns for non-16/18 HPV types were observed in the vaccine arm. Independent risk factors for any oral alpha mucosal HPV among women in the control arm included marital status (adjusted odds ratio [AOR], 3.2; 95% confidence interval [CI], 1.8–5.7 for single compared to married/living as married), number of sexual partners (AOR, 2.4; 95% CI, 1.0–6.1 for ≥4 partners compared to 0–1 partners), chronic sinusitis (AOR, 3.1; 95% CI, 1.5–6.7), and cervical HPV infection (AOR, 2.6; 95% CI, 1.4–4.6). Detection of beta HPV was common (18.6%) and not associated with sexual activity.
Conclusions. Unlike cutaneous HPV types, alpha mucosal HPV types were uncommon in the oral region and were predominately associated with sexual behavior.
Clinical Trials Registration. NCT00128661.
PMCID: PMC3805238  PMID: 24014882
human papillomavirus vaccine; HPV; oropharynx cancer; Costa Rica; Guanacaste; oral HPV DNA
4.  Impact of Human Papillomavirus Vaccination on Cervical Cytology Screening, Colposcopy, and Treatment 
American Journal of Epidemiology  2013;178(5):752-760.
The impact of human papillomavirus (HPV) vaccination on cervical screening, colposcopy, and treatment is incompletely understood. In 2004–2005, investigators in the Costa Rica Vaccine Trial randomized 7,466 women aged 18–25 years, 1:1, to receive HPV vaccination or hepatitis A vaccination. The worst-ever cytology diagnosis and the 4-year cumulative proportions of colposcopy referral and treatment by vaccination arm were compared for 2 cohorts. The total vaccinated cohort included 6,844 women who provided cervical samples. The naive cohort included 2,284 women with no evidence of previous HPV exposure. In the total vaccinated cohort, HPV-vaccinated women had a significant (P = 0.01) reduction in cytological abnormalities: 12.4% for high-grade lesions and 5.9% for minor lesions. Colposcopy referral was reduced by 7.9% (P = 0.03) and treatment by 11.3% (P = 0.24). Greater relative reductions in abnormal cytology (P < 0.001) were observed for HPV-vaccinated women in the naive cohort: 49.2% for high-grade lesions and 18.1% for minor lesions. Colposcopy referral and treatment were reduced by 21.3% (P = 0.01) and 45.6% (P = 0.08), respectively, in the naive cohort. The overall impact on health services will be modest in the first years after vaccine introduction among young adult women, even in regions with high coverage.
PMCID: PMC3755646  PMID: 23843026
cervical cancer; HPV; HPV vaccination; human papillomavirus; screening
5.  Cross-protective vaccine efficacy of the bivalent HPV vaccine against HPV31 is associated with humoral immune responses 
Human Vaccines & Immunotherapeutics  2013;9(7):1399-1406.
Background: We investigated the role of antibody responses as potential mechanism for the cross-protective vaccine-efficacies (VE) observed from randomized clinical trials of the HPV16/18 bivalent vaccine.
Results: HPV31 cases had lower HPV16 antibody levels than controls (OR4th quartile compared with 1st quartile = 0.63; 95%CI: 0.36–1.08; p-trend = 0.03). HPV31 cases were also less likely to have detectable HPV31 neutralization, and HPV16 avidity than controls. No statistically significant differences by HPV18 antibody or HPV45 neutralization were observed among HPV45 cases and controls. Protection against HPV58 was not associated with any of the markers, confirming the specificity of our findings.
Methods: Samples are from three-dose HPV vaccine recipients from the Costa Rica HPV16/18 vaccine trial. Women with a new HPV31, HPV45, or HPV58 infections over four years of follow-up were compared with randomly selected control women—with no new infection with HPV31/45/58—with respect to HPV16 and HPV18 antibody, HPV31, HPV45, and HPV58 neutralization, and HPV16 avidity.
Conclusions: High HPV16 levels and avidity, and the ability to neutralize HPV31 were associated with protection against newly detected HPV31 infections, suggesting that the partial VE demonstrated for HPV31 is likely to be mediated at least in part through antibodies induced by HPV16/18 vaccination.
PMCID: PMC3974884  PMID: 23571174
HPV vaccine; humoral; immune response; cross-protection; mechanisms for protection
6.  Reproductive and hormonal factors and the risk of lung cancer: the EAGLE Study 
Evidence about the role for reproductive and hormonal factors in the etiology of lung cancer in women is conflicting. To clarify this question, we examined 407 female cases and 499 female controls from the Environment And Genetics in Lung cancer Etiology (EAGLE) population-based case-control study. Subjects were interviewed in person using a computer-assisted personal interview to assess demographics, education, smoking history, medical history, occupational history, reproductive and hormonal factors. Associations of interest were investigated using logistic regression models, adjusted for catchment area and age (matching variables), cigarette smoking (status, pack-years, and time since quitting). Additional confounding variables were investigated but did not substantially affect the results. We observed a reduced risk of lung cancer among women with later age at first live birth (≥31 years: OR=0.57, 95%CI=0.31–1.06, p-trend=0.05), later age at menopause (≥51 years: OR=0.49, 95%CI=0.31–0.79, p-trend=0.003), and longer reproductive periods (≥41 years: OR=0.44, 95%CI=0.25–0.79, p-trend=0.01). A reduced risk was also observed for Hormone Replacement Therapy (OR=0.63, 95%CI=0.42–0.95, p=0.03) and oral contraceptive use (OR=0.67, 95%CI=0.45–1.00, p=0.05), but no trend with duration of use was detected. Menopausal status (both natural and induced) was associated with an augmented risk. No additional associations were identified for other reproductive variables. This study suggests that women who continue to produce estrogens have a lower lung cancer risk. Large studies with great number of never smoking women, biomarkers of estrogen and molecular classification of lung cancer are needed for a more comprehensive view of the association between reproductive factors and lung cancer risk.
PMCID: PMC3609937  PMID: 23129166
case-control study; lung cancer; reproductive factors
7.  An investigation of risk factors for renal cell carcinoma by histologic subtype in two case-control studies 
To investigate whether renal cell carcinoma (RCC) histologic subtypes possess different etiologies, we conducted analyses of established RCC risk factors by subtype (clear cell, papillary, chromophobe) in two case-control studies conducted in the United States (1,217 cases, 1,235 controls) and Europe (1,097 cases, 1,476 controls). Histology was ascertained for 706 U.S. cases (58% of total) and 917 European cases (84%) through a central slide review conducted by a single pathologist. For the remaining cases, histology was abstracted from the original diagnostic pathology report. Case-only analyses were performed to compute odds ratios (ORs) and 95% confidence intervals (CI) summarizing subtype differences by age, sex, and race. Case-control analyses were performed to compute subtype-specific ORs for other risk factors using polytomous regression. In case-only analyses, papillary cases (N=237) were older (OR=1.2, 95% CI=1.1–1.4 per 10-year increase), less likely to be female (OR=0.5, 95 % CI=0.4- 0.8) and more likely to be black (OR=2.6, 95% CI=1.8–3.9) compared to clear cell cases (N=1,524). In case-control analyses, BMI was associated with clear cell (OR=1.2, 95% CI=1.1–1.3 per 5kg/m2 increase) and chromophobe RCC (N=80; OR=1.2, 95% CI=1.1- 1.4), but not papillary RCC (OR=1.1, 95% CI=1.0–1.2; test vs. clear cell, P=0.006). No subtype differences were observed for associations with smoking, hypertension or family history of kidney cancer. Our findings support the existence of distinct age, sex and racial distributions for RCC subtypes, and suggest that the obesity-RCC association differs by histology.
PMCID: PMC3717609  PMID: 23150424
Renal cell carcinoma; histology; case-control studies; body mass index
8.  A general binomial regression model to estimate standardized risk differences from binary response data 
Statistics in medicine  2012;32(5):808-821.
Estimates of absolute risks and risk differences are necessary for evaluating the clinical and population impact of biomedical research findings. We have developed a linear-expit regression model (LEXPIT) to incorporate linear and nonlinear risk effects to estimate absolute risk from studies of a binary outcome. The LEXPIT is a generalization of both the binomial linear and logistic regression models. The coefficients of the LEXPIT linear terms estimate adjusted risk differences, while the exponentiated nonlinear terms estimate residual odds ratios. The LEXPIT could be particularly useful for epidemiological studies of risk association, where adjustment for multiple confounding variables is common. We present a constrained maximum likelihood estimation algorithm that ensures the feasibility of risk estimates of the LEXPIT model and describe procedures for defining the feasible region of the parameter space, judging convergence, and evaluating boundary cases. Simulations demonstrate that the methodology is computationally robust and yields feasible, consistent estimators. We applied the LEXPIT model to estimate the absolute five-year risk of cervical precancer or cancer associated with different Pap and human papillomavirus test results in 167,171 women undergoing screening at Kaiser Permanente Northern California. The LEXPIT model found an increased risk due to abnormal Pap test in HPV-negative that was not detected with logistic regression. Our R package blm provides free and easy-to-use software for fitting the LEXPIT model.
PMCID: PMC3982929  PMID: 22865328
Absolute risk; Binomial regression; Constrained maximization; Logistic regression; Risk difference
9.  Are Women Who Smoke at Higher Risk for Lung Cancer Than Men Who Smoke? 
American Journal of Epidemiology  2013;177(7):601-612.
Worldwide lung cancer incidence is decreasing or leveling off among men, but rising among women. Sex differences in associations of tobacco carcinogens with lung cancer risk have been hypothesized, but the epidemiologic evidence is conflicting. We tested sex-smoking interaction in association with lung cancer risk within a population-based case-control study, the Environment and Genetics in Lung Cancer Etiology (EAGLE) Study (Lombardy, Italy, 2002–2005). Detailed lifetime smoking histories were collected by personal interview in 2,100 cases with incident lung cancer and 2,120 controls. Odds ratios and 95% confidence intervals for pack-years of cigarette smoking were estimated by logistic regression, adjusted for age, residence area, and time since quitting smoking. To assess sex-smoking interaction, we compared the slopes of odds ratios for logarithm of pack-years in a model for men and women combined. Overall, the slope for pack-years was steeper in men (odds ratio for female-smoking interaction = 0.39, 95% confidence interval: 0.24, 0.62; P < 0.0001); after restriction to ever smokers, the difference in slopes was much smaller (odds ratio for interaction = 0.63, 95% confidence interval: 0.29, 1.37; P = 0.24). Similar results were found by histological type. Results were unchanged when additional confounders were evaluated (e.g., tobacco type, inhalation depth, Fagerström-assessed nicotine dependence). These findings do not support a higher female susceptibility to tobacco-related lung cancer.
PMCID: PMC3657535  PMID: 23425629
case-control studies; lung cancer; sex differences; smoking
10.  Precursors in cancer epidemiology: aligning definition and function 
A precursor of a disease is a definable pathologic state that progresses directly to disease without a known intermediate step, and whose presence substantially increases the likelihood of disease. Precancers, or precursors of cancer, can help provide detail about the dynamic pathogenesis process before clinical disease. Thereby, ascertainment of properly defined precancers can increase precision of estimates and power in epidemiologic and clinical studies. Besides providing targets for direct treatment and improving tools for risk assessment in screening programs, precancers can help establish temporal ordering of cause and effect; can identify relatively homogeneous subsets of cancer that have passed through a given precancer state; and provide a basis for choosing high-risk individuals for detailed longitudinal study. Although the most appropriate definition of the precancer will vary with its function in particular research or clinical applications, the proportion of cancers that progress from the precancer and risk of cancer progressing from the precancer can be important measures of the value of a precancer in translational efforts.
PMCID: PMC3738010  PMID: 23549395
11.  High load for most high risk human papillomavirus genotypes is associated with prevalent cervical cancer precursors but only HPV16 load predicts the development of incident disease 
Cervicovaginal human papillomavirus (HPV) viral load has been purported as a potential marker for the detection of high-grade cervical intraepithelial neoplasia or cancer (≥CIN2). To examine disease association with type-specific viral load for the full-range of anogenital HPV infections, we conducted cross-sectional and prospective analyses of ∼2,000 HPV-infected women from a 10,000-woman population-based study in Guanacaste, Costa Rica with 7 years of follow-up. Cervical specimens were tested for >40 HPV types using a MY09/MY11 L1 consensus primer PCR method with type-specific dot blot hybridization and PCR signal intensity as a measure of viral load. A positive association was observed between prevalent ≥CIN2 and high viral load compared to low viral load for women with baseline single HPV16 infections (OR = 19.2, 95% CI = 4.4–83.2) and single non-16 carcinogenic infections (OR = 9.2, 95% CI = 2.1–39.9). Inclusion of women with multiple HPV types did not substantially change these associations. In prospective follow-up, only women infected with HPV16 alone (OR = 27.2, 95% = 3.5-213.5) had a strong association between high viral load and incident ≥CIN2; non-16 carcinogenic high viral load was not associated with incident ≥CIN2 (OR = 0.7, 95% CI = 0.2–1.9). Single noncarcinogenic type viral load was not associated with increased risk of prevalent or incident ≥CIN2 (OR = 1.2 and 1.1, respectively). In conclusion, carcinogenic high viral load was associated with prevalent ≥CIN2; however HPV16 was uniquely associated with incident ≥CIN2. The extent to which these observations can be translated into clinical practice must be rigorously examined in the context of the method of viral load measurement and the type-specific differences observed for incident ≥CIN2.
PMCID: PMC3962984  PMID: 17722112
human papillomavirus; viral load; genotype; screening
12.  Elevated methylation of HPV16 DNA is associated with the development of high grade cervical intraepithelial neoplasia 
We explored the association of HPV16 DNA methylation with age, viral load, viral persistence, and risk of incident and prevalent high grade CIN (CIN2+) in serially collected specimens from the Guanacaste, Costa Rica cohort. 273 exfoliated cervical cell specimens (diagnostic and pre-diagnostic) were selected: 1) 92 with HPV16 DNA clearance (controls), 2) 72 with HPV16 DNA persistence (without CIN2+), and 3) 109 with CIN2+. DNA was extracted, bisulfite converted and methylation was quantified using pyrosequencing assays at 66 CpGs across the HPV genome. The Kruskal-Wallis test was used to determine significant differences among groups, and receiver operating characteristic curve analyses were used to evaluate how well methylation identified women with CIN2+. In diagnostic specimens, 88% of CpG sites had significantly higher methylation levels in CIN2+ after correction for multiple tests compared with controls. The highest AUC was 0.82 for CpG site 6457 in L1, and a diagnostic sensitivity of 91% corresponded to a specificity of 60% for CIN2+. Prospectively, 17% of CpG sites had significantly higher methylation in pre-diagnostic CIN2+ specimens (median time of 3 years before diagnosis) vs. controls. The strongest pre-diagnostic CpG site was 6367 in L1 with an AUC of 0.76. Age-stratified analyses suggested that women older than the median age of 28 years have an increased risk of precancer associated with high methylation. Higher methylation in CIN2+ cases was not explained by higher viral load. We conclude that elevated levels of HPV16 DNA methylation may be useful to predict concurrently diagnosed as well as future CIN2+.
PMCID: PMC3493709  PMID: 22847263
HPV16; methylation; epidemiology; receiver operating curve; biomarker
13.  Glutathione S-transferase L1 multiplex serology as a measure of cumulative infection with human papillomavirus 
BMC Infectious Diseases  2014;14:120.
Several assays are used to measure type-specific serological responses to human papillomavirus (HPV), including the bead-based glutathione S-transferase (GST)-L1 multiplex serology assay and virus-like particle (VLP)-based ELISA. We evaluated the high-throughput GST-L1, which is increasingly used in epidemiologic research, as a measure of cumulative HPV infection and future immune protection among HPV-unvaccinated women.
We tested enrollment sera from participants in the control arm of the Costa Rica Vaccine Trial (n = 488) for HPV16 and HPV18 using GST-L1, VLP-ELISA, and two assays that measure neutralizing antibodies (cLIA and SEAP-NA). With statistical adjustment for sampling, we compared GST-L1 serostatus to established HPV seropositivity correlates and incident cervical HPV infection using odds ratios. We further compared GST-L1 to VLP-ELISA using pair-wise agreement statistics and by defining alternate assay cutoffs.
Odds of HPV16 GST-L1 seropositivity increased with enrollment age (OR = 1.20 per year, 95%CI 1.03-1.40) and lifetime number of sexual partners (OR = 2.06 per partner, 95%CI 1.49-2.83), with similar results for HPV18. GST-L1 seropositivity did not indicate protection from incident infection over 4 years of follow-up (HPV16 adjusted OR = 1.72, 95%CI 0.95-3.13; HPV18 adjusted OR = 0.38, 95%CI 0.12-1.23). Seroprevalence by GST-L1 (HPV16 and HPV18, respectively) was 5.0% and 5.2%, compared to 19.4% and 23.8% by VLP-ELISA, giving positive agreement of 39.2% and 20.8%. Lowering GST-L1 seropositivity cutoffs improved GST-L1/VLP-ELISA positive agreement to 68.6% (HPV16) and 61.5% (HPV18).
Our data support GST-L1 as a marker of cumulative HPV infection, but not immune protection. At lower seropositivity cutoffs, GST-L1 better approximates VLP-ELISA.
PMCID: PMC3973893  PMID: 24588945
14.  Genome-wide Association Study Identifies Two Susceptibility Loci for Osteosarcoma 
Nature genetics  2013;45(7):799-803.
Osteosarcoma is the most common primary bone malignancy of adolescents and young adults. In order to better understand the genetic etiology of osteosarcoma, we performed a multi-stage genome-wide association study (GWAS) consisting of 941 cases and 3,291 cancer-free adult controls of European ancestry. Two loci achieved genome-wide significance: rs1906953 at 6p21.3, in the glutamate receptor metabotropic 4 [GRM4] gene (P = 8.1 ×10-9), and rs7591996 and rs10208273 in a gene desert on 2p25.2 (P = 1.0 ×10-8 and 2.9 ×10-7). These two susceptibility loci warrant further exploration to uncover the biological mechanisms underlying susceptibility to osteosarcoma.
PMCID: PMC3910497  PMID: 23727862
15.  From differences in means between cases and controls to risk stratification: A business plan for biomarker development 
Cancer discovery  2013;3(2):148-157.
Researchers developing biomarkers for early detection can determine the potential for clinical benefit at early stages of development. We provide the theoretical background showing the quantitative connection between biomarker levels in cases and controls and clinically meaningful risk measures and a spreadsheet for researchers to use in their own research. We provide researchers with tools to decide whether a test is useful, whether it needs technical improvement, whether it may only work in specific populations, or whether any further development is futile. The methods described here apply to any method that aims to estimate risk of disease based on biomarkers, clinical tests, genetics, environment or behavior.
PMCID: PMC3570740  PMID: 23299199
biomarker; risk stratification; screening; predictive value; likelihood ratio
17.  The association between chronic renal failure and renal cell carcinoma may differ between black and white Americans 
Cancer causes & control : CCC  2012;24(1):167-174.
In the United States, renal cell carcinoma (RCC) incidence is higher among blacks than among whites. Risk of RCC is elevated among end-stage renal disease patients, although no studies have looked at differences by race in the relationship between chronic renal failure and RCC.
We investigated RCC risk in relation to chronic renal failure in a population-based case-control study of blacks and whites in Chicago and Detroit. Data, including information on kidney disease, were collected from interviews with 1,217 RCC cases (361 blacks, 856 whites) and 1,235 controls (523 blacks, 712 whites). Odds ratios (OR) and 95% confidence intervals (CI) were estimated using unconditional logistic regression.
Risk of RCC was increased in relation to chronic renal failure (OR 4.7, 95% CI 2.2–10.1) and dialysis (OR 18.0, 95% CI 3.6–91). The association remained after defining exposure as those who had chronic renal failure ≥10 years prior to RCC diagnosis. Chronic renal failure was more strongly associated with RCC among blacks than among whites (OR 8.7, 95% CI 3.3–22.9 and 2.0, 0.7–5.6 respectively; Pinteraction=0.03) and among those without a history of diabetes relative to diabetic subjects (OR 8.3, 95% CI 3.1–22.7 and 1.9, 0.6–5.9 respectively; Pinteraction=0.03).
These results suggest that chronic renal failure is a strong risk factor for RCC, particularly among black and non-diabetic subjects. Our findings of differences in risk estimates by race, to our knowledge the first such report, require replication.
PMCID: PMC3531044  PMID: 23179659
renal cell carcinoma; kidney cancer; chronic renal failure; end-stage renal disease; racial disparities
18.  Serum leptin and adiponectin levels and risk of renal cell carcinoma 
Obesity (Silver Spring, Md.)  2013;21(7):1478-1485.
The incidence of renal cell carcinoma (RCC) has increased rapidly in the U.S., particularly among African Americans. Despite a well-established link between obesity and RCC, the mechanism through which obesity increases cancer risk has yet to be established. Adipokines, such as leptin and adiponectin, may link obesity and cancer, with different quantitative effects by race. We evaluated the association between leptin and adiponectin concentrations and RCC risk among Caucasians (581 cases, 558 controls) and African Americans (187 cases, 359 controls) in a case-control study conducted in Detroit and Chicago. Odds ratios(ORs) and 95% confidence intervals(95%CIs) were estimated using unconditional logistic regression. Among controls, Caucasians had higher median adiponectin than African Americans (males: 8.2 vs. 7.0µg/ml, p=0.001; females: 13.4 vs. 8.4µg/ml, p<0.0001), and lower median leptin than African Americans (males: 11.8 vs. 14.1ng/ml, p=0.04; females: 28.3 vs. 45.9ng/ml, p<0.0001). Among Caucasians, the ORs for RCC comparing the highest (Q4) to the lowest (Q1) sex-specific quartile of leptin were 3.2 (95%CI:1.9–5.2) for males and 4.7 (95%CI:2.6–8.6) for females. Serum leptin was not significantly associated with RCC among African American males (OR 1.5, 95%CI:0.7–3.1) or females (OR 2.1, 95%CI:0.8–5.5). Higher adiponectin was associated with RCC risk among African American males (Q4 vs. Q1: OR 2.3, 95%CI:1.1–4.6) and females (OR 2.1, 95%CI:1.2–6.7), but not significantly among Caucasian males (OR 1.6, 95%CI:0.99–2.7) and females (OR 1.6, 95%CI:0.9–3.1). In conclusion, we observed an association between both leptin and adiponectin concentrations and risk of RCC, which may differ by race. Confirmation in further investigations is needed.
PMCID: PMC3742622  PMID: 23666639
19.  Effectiveness of a simple rapid HPV DNA test in rural Nigeria 
Success of the new HPV DNA test for low-resource settings (careHPV™ test, QIAGEN Gaithersburg, Inc.; Gaithersburg, MD) requires good test performance when operated by personnel with limited laboratory experience. We evaluated the transferability, reliability, and accuracy of the careHPV test nested within a cervical screening project in a large Nigerian village. CareHPV testing was performed on screen-positive (n=345) and screen-negative (n=42) women attending colposcopy (68.3% of referred). Biopsies of abnormal-appearing areas were processed and read in the U.S. CareHPV specimens taken immediately before colposcopy were processed up to four times [in the field] by two secondary school graduates without laboratory experience, trained for this study. Specifically, QIAGEN Gaithersburg trained a laboratory-inexperienced U.S. researcher, who trained the first local technician who, in turn, trained the second. Residual specimens were sent to the U.S. for MY09/MY11 PCR testing for 13 carcinogenic genotypes (HPV16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 68) plus HPV66 (included in careHPV). Intra-rater agreement was 98.8% (Kappa=.97) and 98.9% (Kappa=.97) for technicians 1 and 2, respectively while inter-rater agreement was 96.3% (Kappa=.90). Agreement with MY09/MY11 PCR (virologic reference standard) was 89.3% (Kappa=.73) with 74.2% sensitivity and 95.7% specificity. The careHPV test detected 12 (80%) of 15 histologically-confirmed cervical intraepithelial neoplasia grade 2 (CIN2) or worse lesions, with an estimated 83.0% specificity to detect < CIN2. In a challenging low-resource setting with minimal intervention, the careHPV test performed adequately with high specificity but possibly lower sensitivity than HPV DNA tests currently used in controlled situations.
PMCID: PMC3404249  PMID: 22473652
screening; cervical cancer prevention; HPV DNA testing; test accuracy
20.  Human Papillomavirus DNA Methylation as a Potential Biomarker for Cervical Cancer 
Sexually transmitted carcinogenic Human Papillomavirus (HPV) infections are extraordinarily prevalent worldwide. However, most incident HPV infections clear within a few years, whereas a small minority persists to invasive cancer. Recent studies indicate that detection of methylated viral DNA may distinguish women with cervical intraepithelial neoplasia grade 2+ (CIN2+) from those with a carcinogenic HPV type infection that shows no evidence of CIN2+. Several studies have reported a positive association between methylation of CpG sites in the L1 gene and CIN2+, while there are inconclusive results regarding methylation of CpG sites in the Upstream Regulatory Region (URR). In this review, we summarize the current state of knowledge on HPV DNA methylation in cervical carcinogenesis, and discuss the merits of different methods used to measure HPV DNA methylation. To follow the promising leads, we suggest future studies to validate the use of methylated carcinogenic HPV DNA as a predictive and/or diagnostic biomarker for risk of cervical cancer among HPV-positive women.
PMCID: PMC3664203  PMID: 23035178
human papillomavirus; methylation; cervical cancer; biomarker; epigenetics
21.  Methylation of HPV18, HPV31, and HPV45 Genomes and Cervical Intraepithelial Neoplasia Grade 3 
Persistent infections with carcinogenic human papillomavirus (HPV) types are the necessary cause of cervical cancer. We recently demonstrated that the HPV16 genome is strongly methylated in cervical precancer compared with transient infections. However, the extent of methylation in other HPV types and its role in progression to cancer is poorly understood.
We analyzed whole-genome methylation patterns of the three next most carcinogenic HPV genotypes: HPV31 (closely related to HPV16), and two other closely related types, HPV18 and HPV45. DNA was extracted from cervical cytology specimens from 92 women with precancer and 96 women infected with HPV31, HPV18, or HPV45, but who had no cytological or histological abnormalities. After bisulfite modification, genome-wide pyrosequencing was performed covering 80–106 sites. We calculated differences in median methylation, odds ratios, areas under the curve, and Spearman rank correlation coefficients for methylation levels between different sites. All statistical tests were two-sided.
For all three HPV types, we observed strongly elevated methylation levels at multiple CpG sites in the E2, L2, and L1 regions among women with cervical intraepithelial neoplasia grade 3 compared with women with transient infections. We observed high correlation of methylation patterns between phylogenetically related types. The highest areas under the curve were 0.81 for HPV31, 0.85 for HPV18, and 0.98 for HPV45. Differential methylation patterns in cervical intraepithelial neoplasia grade 3 patients with multiple infections suggest that methylation can clarify which of the infections is causal.
Carcinogenic HPV DNA methylation indicates transforming HPV infections. Our findings show that methylation of carcinogenic HPV types is a general phenomenon that warrants development of diagnostic assays.
PMCID: PMC3571257  PMID: 23093560
22.  A regression model for risk difference estimation in population-based case–control studies clarifies gender differences in lung cancer risk of smokers and never smokers 
Additive risk models are necessary for understanding the joint effects of exposures on individual and population disease risk. Yet technical challenges have limited the consideration of additive risk models in case–control studies.
Using a flexible risk regression model that allows additive and multiplicative components to estimate absolute risks and risk differences, we report a new analysis of data from the population-based case–control Environment And Genetics in Lung cancer Etiology study, conducted in Northern Italy between 2002–2005. The analysis provides estimates of the gender-specific absolute risk (cumulative risk) for non-smoking- and smoking-associated lung cancer, adjusted for demographic, occupational, and smoking history variables.
In the multiple-variable lexpit regression, the adjusted 3-year absolute risk of lung cancer in never smokers was 4.6 per 100,000 persons higher in women than men. However, the absolute increase in 3-year risk of lung cancer for every 10 additional pack-years smoked was less for women than men, 13.6 versus 52.9 per 100,000 persons.
In a Northern Italian population, the absolute risk of lung cancer among never smokers is higher in women than men but among smokers is lower in women than men. Lexpit regression is a novel approach to additive-multiplicative risk modeling that can contribute to clearer interpretation of population-based case–control studies.
PMCID: PMC3840559  PMID: 24252624
Additive risk; Absolute risk; Case–control study; EAGLE; Lung cancer; Risk assessment; Sex factors; Smoking
23.  Body Mass Index and Renal Cell Cancer: The Influence of Race and Sex 
Epidemiology (Cambridge, Mass.)  2012;23(6):821-828.
Obesity is a risk factor for renal cell (or renal) cancer. The increasing prevalence of obesity may be contributing to the rising incidence of this cancer over the past several decades. The effects of early-age obesity and change in body mass index (BMI) on renal cancer have been studied less thoroughly, and the influence of race has never been formally investigated.
Using data gathered as part of a large case-control study of renal cancer (1,214 cases and 1,234 controls), we investigated associations with BMI at several time points, as well as with height. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were computed using logistic regression modeling. Race- and sex-stratified analyses were conducted to evaluate subgroup differences.
Obesity (BMI ≥ 30 kg/m2) early in adulthood (OR=1.6 [95% CI=1.1 to 2.4]) and 5 years before diagnosis (1.6 [1.1 to 2.2]) was associated with renal cancer. The association with early-adult obesity was stronger among whites than blacks (Test for interaction, P=0.006), while the association with obesity near diagnosis was marginally stronger in women than men (Test for interaction, P=0.08). The strongest association with renal cancer was observed for obese whites both in early adulthood and prior to interview (2.6 [1.5 to 4.4]); this association was not present among blacks. Estimates of the annual excess rate of renal cancer (per 100,000 persons) attributed to both overweight and obesity (BMI > 25 kg/m2) ranged from 9.9 among black men to 5.6 among white women.
Obesity, both early and later in life, is associated with an increased risk of renal cancer. The association with early obesity appears to be stronger among whites than blacks.
PMCID: PMC3466395  PMID: 23007040
24.  Prevalence of and Risk Factors for Anal Human Papillomavirus Infection Among Young Healthy Women in Costa Rica 
The Journal of Infectious Diseases  2012;206(7):1103-1110.
Background. Anal cancer is caused by human papillomavirus (HPV), yet little is known about anal HPV infection among healthy young women.
Methods. A total of 2017 sexually active women in the control arm of an HPV-16/18 vaccine trial had a single anal specimen collected by a clinician at the 4-year study visit. Samples were tested for HPV by SPF10 PCR/DEIA/LiPA25, version 1.
Results. A total of 4% of women had HPV-16, 22% had oncogenic HPV, and 31% had any HPV detected in an anal specimen. The prevalence of anal HPV was higher among women who reported anal intercourse, compared with those who did not (43.4% vs 28.4%; P < .001). Among women who reported anal intercourse, cervical HPV (adjusted odds ratio [aOR], 5.3 [95% confidence interval {CI}, 3.4–8.2]), number of sex partners (aOR, 2.2 [95% CI, 1.1–4.6] for ≥4 partners), and number of anal intercourse partners (aOR, 1.9 [95% CI, 1.1–3.3] for ≥2 partners) were independent risk factors for anal HPV detection. Among women who reported no anal intercourse, cervical HPV (aOR, 4.7 [95% CI, 3.7–5.9]), number of sex partners (aOR, 2.4 [95% CI, 1.7–3.4] for ≥4 partners), and report of anal fissures (aOR, 2.3 [95% CI, 1.1–4.8]) were associated with an increased odds of anal HPV detection.
Conclusion. Anal HPV is common among young women, even those who report no anal sex, and was associated with cervical HPV infection. Anal fissures in women who report never having had anal intercourse may facilitate HPV exposure.
Clinical Trials Registration. NCT00128661.
PMCID: PMC3499109  PMID: 22850119
25.  Clinical Utility in Evaluation of Risk Models 
American Journal of Epidemiology  2012;176(6):495-496.
PMCID: PMC3491966  PMID: 22875758

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