Risk estimates for persistent high-risk human papillomavirus infections as surrogate endpoints of progressive cervical disease critically depend on reference category: analysis of the combined prospective cohort of the New Independent States of the Former Soviet Union and Latin American Screening Studies

Summary

To make feasible future clinical trials with new-generation human papillomavirus (HPV) vaccines, novel virological surrogate endpoints of progressive disease have been proposed, including high-risk HPV (HR-HPV) persistence for six months (6M+) or 12 months (12M+). The risk estimates (relative risks [RRs]) of these ‘virological endpoints’ are influenced by several variables, not yet validated adequately. We compared the impact of three referent groups: (i) HPV-negative, (ii) HPV-transient, (iii) HPV-mixed outcome on the risk estimates for 6M+ or 12M+ HR-HPV persistence as predictors of progressive disease. Generalized estimating equation models were used to estimate the strength of 6M+ and 12M+ HR-HPV persistence with disease progression to squamous intraepithelial lesions (SILs), cervical intraepithelial neoplasia (CIN) grade 1 +, CIN2+, CIN/SIL endpoints, comparing three optional reference categories (i)-(iii) in a prospective sub-cohort of 1865 women from the combined New Independent States of the Former Soviet Union (NIS) and Latin American Screening (LAMS) studies cohort ( n = 15,301). The RRs of these viral endpoints as predictors of progressive disease are affected by the length of viral persistence (6M+ or 12M+) and the surrogate endpoint (SIL, CIN1, CIN2, CIN/SIL). Most dramatic is the effect of the referent group used in risk estimates, with the HPV-negative referent group giving the highest and most consistent RRs for both 6M+ and 12M+ viral persistence, irrespective of which surrogate is used. In addition to deciding on whether to use 6M+ or 12M+ persistence criteria, and cytological, histological or combined surrogate endpoints, one should adopt the HPV-negative referent group as the gold standard in all future studies using viral persistence as the surrogate endpoint of progressive disease.

Epidemiological, clinical and viral determinants of the increased prevalence of high-risk human papillomavirus (HPV) infections in elderly women

BACKGROUND

Population-based studies have reported a second peak of human papillomavirus (HPV) prevalence among women > 55 years, but reasons for this U-shaped HPV prevalence curve are poorly understood.

OBJECTIVES

To analyse determinants of high-risk HPV (HR-HPV) infections among postmenopausal women.

STUDY DESIGN AND METHODS

A cohort of 3,187 women was stratified into three age categories: i) youngest age group < 25 years (n = 1.103); ii) women between 26-55 years (n = 2.004), and iii) women > 55 years (n = 80), analysed for epidemiological, clinical and virological determinants of their HR-HPV infections. Real-time PCR was used for HPV genotyping, analysis of viral loads for HPV16, 18/45, 31, 33/52/58, 35 and 39, and load of integrated HPV16.

RESULTS

Age-standardised prevalence of HR-HPV infections showed a second peak among women > 55 years, with a perfect U-shaped curve (R2 = 0.966). The factors explaining this increased HR-HPV prevalence among older women include: i) cohort effect, ii) higher viral loads for HR-HPV types with cubic model curve (R2 = 0.714) for HPV 16, iii) distinct shift (p = 0.0001) from multiple-type infections to single HR-HPV types, iv) transition from episomal to integrated HPV16 (p = 0.009), v) higher load of integrated HPV16 (p = 0.009), and, vi) higher proportion of incident infections, higher rate of viral persistence, and lower rate of HR-HPV clearance.

CONCLUSIONS

These data suggest that in women who fail to eradicate their HR-HPV infection until menopause, selection of integrated viral clone has taken place, driving the process towards progressing disease. Consequent to this, most of the HR-HPV infections in women > 55 years were associated with high-grade CIN or invasive carcinoma.

Factors predicting persistence of high-risk human papillomavirus (HPV) infections in women prospectively followed-up in three New Independent States (NIS) of the former Soviet Union

BACKGROUND

We completed an analysis of the factors predicting the persistence of high risk (HR) HPV infections in women participating in a multicenter screening trial in three NIS countries.

METHODS

The 543 baseline HR HPV-positive women included in this analysis are derived from a sub-cohort of 887 women who were prospectively followed-up for a mean of 21.6 months (range: 0.5-42.9) as a part of a multi-center screening study in three NIS countries (the NIS cohort study; n = 3,187 women). Of these 543 women, 273 showed persistent HR-HPV in serial Hybrid Capture II (HCII) testing during the follow-up (Group 1), whereas 270 women cleared their infection (Group 2). These two groups were compared with their epidemiological, clinical, and virological data (HCII, PCR) to disclose the factors predicting persistent HR-HPV infection.

RESULTS

Women with persistent HR-HPV infections were significantly younger (27.3 yrs) than those who cleared their infection (29.1 yrs) (p = 0.006), and their follow-up time was shorter; 14.1 and 21 months, respectively (p = 0.0001). Both variables were treated as confounders in the multivariate analyses. Of the 66 recorded epidemiological variables, only being a current smoker proved to be an independent predictor (OR 1.693; 95% CI 1.114-2.573; p=0.014). Baseline colposcopy, biopsy or Pap smear did not predict HPV persistence, whereas an incident or persistent abnormal Pap during the follow-up were independent predictors in a multivariate model (p = 0.005), together with the high viral load (HCII RLU/CO at 100 pg/ml cut-off), and HR HPV positive PCR test (p = 0.0001). When all significant variables were entered in the regression model, only the follow-up time (OR 0.950, 95% CI 0.924-0.976; p = 0.0001) and HR-HPV positive PCR (OR 4.169, 95% CI 1.741-9.987; p = 0.001), remained independent predictors.

CONCLUSIONS

While several factors were related to HR-HPV persistence in univariate analysis and when adjusted for age and follow-up time as confounders, the only independent predictors in the multivariate regression model were follow-up time and HR-HPV positive PCR. Clearly more data are needed on type-specific persistence and HPV integration as its predictors.