Performance of p16/Ki-67 immunostaining to detect cervical cancer precursors in a colposcopy referral population

Screening for cervical cancer precursors with p16/Ki-67 dual-stained cytology: results of the PALMS study

Background

Pap cytology is known to be more specific but less sensitive than testing for human papillomavirus (HPV) for the detection of high-grade cervical intraepithelial neoplasia (CIN2+). We assessed whether p16/Ki-67 dual-stained cytology, a biomarker combination indicative of transforming HPV infections, can provide high sensitivity for CIN2+ in screening while maintaining high specificity. Results were compared with Pap cytology and HPV testing.

Methods

A total of 27349 women 18 years or older attending routine cervical cancer screening were prospectively enrolled in five European countries. Pap cytology, p16/Ki-67 immunostaining, and HPV testing were performed on all women. Positive test results triggered colposcopy referral, except for women younger than 30 years with only positive HPV test results. Presence of CIN2+ on adjudicated histology was used as the reference standard. Two-sided bias-corrected McNemar P values were determined.

Results

The p16/Ki-67 dual-stained cytology positivity rates were comparable with the prevalence of abnormal Pap cytology results and less than 50% of the positivity rates observed for HPV testing. In women of all ages, dual-stained cytology was more sensitive than Pap cytology (86.7% vs 68.5%; P < .001) for detecting CIN2+, with comparable specificity (95.2% vs 95.4%; P = .15). The relative performance of the tests was similar in both groups of women: younger than age 30 and 30 years or older. HPV testing in women 30 years or older was more sensitive than dual-stained cytology (93.3% vs 84.7%; P = .03) but less specific (93.0% vs 96.2%; P < .001).

Conclusions

The p16/Ki-67 dual-stained cytology combines superior sensitivity and noninferior specificity over Pap cytology for detecting CIN2+. It suggests a potential role of dual-stained cytology in screening, especially in younger women where HPV testing has its limitations.

Dual immunostaining of cervical cytology specimens with atypical squamous cells for p16/Ki-67 does not exclude the existence of a high-grade squamous intraepithelial lesion

This study was conducted to evaluate the accuracy of p16/Ki-67 dual immunostaining compared to high-risk human papillomavirus (HR-HPV) DNA testing for cervical intraepithelial neoplasia (CIN) in women with atypical squamous cells, cytology not excluding high-grade squamous intraepithelial lesion (ASC-H). Data were collected from 73 patients diagnosed to have ASC-H on a Pap smear who were HPV genotyped and had histological examination of a cervical biopsy. The CINtecPLUS kit was used on residual liquid-based material, and the immunoreactivity of dual-stained cells was graded according to the number as follows: G1 (1-5 positive cells), G2 (6-10), G3 (11-20), and G4 (> 20). Accuracy was evaluated based on the histological examination of colposcopy-guided biopsy or cervical conization on follow-up. Of the 70 patients with available data, positive p16/Ki-67 was associated with histological severity as follows: 15% in negative histology, 67% in CIN 1, 90% in CIN 2, and 100% in CIN 3. The average grade of positive p16/Ki-67 staining also increased from 0.2 in histologically negative cases to 1.2 in CIN 1, 2.4 in CIN 2, and 2.9 in CIN 3 (p < 0.01). For patients with CIN 2 or higher, p16/Ki-67 had a sensitivity of 94.6% and a specificity of 75.8%, while HR-HPV testing showed a sensitivity of 67.6% and a specificity of 66.7%. p16/Ki-67 immunostaining demonstrated better accuracy than HR-HPV for detecting CIN 2 or higher in patients with ASC-H cytology. Given the higher concordance with histological diagnosis, the grading system of positive p16/Ki-67 can be a useful adjunct for predicting high-grade lesions in clinical practice.

Prognostic value of p16-INK4A protein in women with negative or CIN1 histology result: a follow-up study

P16-INK4A overexpression has been proposed as a prognostic marker to manage the follow up of women with positive cytology and/or HPV test but without high-grade cervical intraepithelial neoplasia (CIN2+). This study measures the relative risk (RR) of CIN2+ of p16 positive versus negative in these women. All the women referred to colposcopy from October 2008 to September 2010 with negative or CIN1 colposcopy-guided biopsy were included in the study; women surgically treated or having a CIN2-3 were excluded. All baseline biopsies were dyed with hematoxylin and eosin and p16. Women were followed up according to screening protocols, with cytology or colposcopy at 6 or 12 months. CIN2/3 RRs and 95% confidence intervals (95%CI) were computed. Of 442 eligible women, 369 (83.5%) had at least one follow-up episode. At baseline, 113 (30.6%) were CIN1, 248 (67.2%) negative, and 8 (2.2%) inadequate histology; 293 (79.4%) were p16-negative, 64 (17.3%) p16 positive and 12 (3.2%) not valid. During follow up, we found ten CIN2 and three CIN3; of these, six were p16 positive (sensitivity 46%, 95% CI 19-75). The absolute risk among p16 positives was 9.4/100 compared to 1.7/100 of the p16 negatives (RR 5.5; 95% CI 1.7-17.4). The risk was also higher for CIN1 than for histologically negative women (RR 4.4; 95% CI 1.3-14.3). The RR for p16 in CIN1 did not change (RR 5.2; 95% CI 0.6-47.5). P16 overexpression is a good candidate for modulating follow-up intensity after a negative colposcopy but is limited by its low prospective sensitivity.

Prospects for prevention of HPV-driven oropharynx cancer

Prevention of HPV-associated cancers can take two forms-one through prevention of infection via prophylactic HPV vaccination, and one through interruption of disease progression through early identification (i.e.: screening) and treatment. Primary prevention via vaccination seems promising, as a proof-of-principal study demonstrated high vaccine efficacy against one-time detection of oral HPV16/18 infection. In addition to the direct benefit of vaccination, indirect protection from reduced genital HPV infection should also reduce oral HPV exposure at the individual level. Yet, for the current unvaccinated cohorts who will bear the burden of non-cervical HPV-associated cancers for the foreseeable future, no secondary prevention opportunities exist, as the field has not yet validated any screening methods for non-cervical HPV associated cancers. Serum HPV16 E6 antibody data suggest that this test might one day be able to detect many of the at-risk patients prior to tumor development. For any biomarker that proves valid and reliable, transitioning into clinical practice will require additional research focused on (1) diagnostics, (2) effective intervention, and (3) observed reductions in cancer mortality.

Chromosomal gains measured in cytology samples from women with abnormal cervical cancer screening results

OBJECTIVE

Chromosomal gains at 3q26, 5p15 and 20q13 have been described in cervical precancer and cancer. We evaluated a novel fluorescence in situ hybridization (FISH) assay that detects gains at these three loci simultaneously as a possible biomarker for detecting cervical precancer.

METHODS

Chromosomal copy numbers at 3q26, 5p15, 20q13 and the centromere of chromosome7 (cen7) in liquid-based cytology specimens from 168 women enrolled in the Biopsy Study were determined by FISH. The number of cells with ≥ 3 or ≥ 4 signals for a genomic locus was enumerated and diagnostic test performance measures were calculated using receiver operating characteristic (ROC) analyses. Sensitivity and specificity values were determined for the detection of CIN2+ and/or HSIL.

RESULTS

The median number of cells with ≥ 3 signals increased with the severity of cervical lesion for each genomic locus (p-trend<0.02 for each locus). ROC analysis for the number of cells with ≥ 3 signals resulted in area under the curve values of 0.70 (95% CI: 0.54-0.86), 0.67 (0.52-0.83), 0.67 (0.51-0.83) and 0.78 (0.64-0.92) for 3q26, 5p15, 20q13 and cen7, respectively, for the detection of CIN2+ and/or HSIL. Positivity for gains at multiple loci resulted in only slightly better test performance measures than those for the individual probes for four distinct combinations of probes.

CONCLUSIONS

Chromosomal gains at 3q26, 5p15, 20q13 and cen7 are associated with severity of cervical lesions. Further studies are required to quantify risk stratification of FISH assays for cervical cancer screening.

Semantic focusing allows fully automated single-layer slide scanning of cervical cytology slides

Liquid-based cytology (LBC) in conjunction with Whole-Slide Imaging (WSI) enables the objective and sensitive and quantitative evaluation of biomarkers in cytology. However, the complex three-dimensional distribution of cells on LBC slides requires manual focusing, long scanning-times, and multi-layer scanning. Here, we present a solution that overcomes these limitations in two steps: first, we make sure that focus points are only set on cells. Secondly, we check the total slide focus quality. From a first analysis we detected that superficial dust can be separated from the cell layer (thin layer of cells on the glass slide) itself. Then we analyzed 2,295 individual focus points from 51 LBC slides stained for p16 and Ki67. Using the number of edges in a focus point image, specific color values and size-inclusion filters, focus points detecting cells could be distinguished from focus points on artifacts (accuracy 98.6%). Sharpness as total focus quality of a virtual LBC slide is computed from 5 sharpness features. We trained a multi-parameter SVM classifier on 1,600 images. On an independent validation set of 3,232 cell images we achieved an accuracy of 94.8% for classifying images as focused. Our results show that single-layer scanning of LBC slides is possible and how it can be achieved. We assembled focus point analysis and sharpness classification into a fully automatic, iterative workflow, free of user intervention, which performs repetitive slide scanning as necessary. On 400 LBC slides we achieved a scanning-time of 13.9±10.1 min with 29.1±15.5 focus points. In summary, the integration of semantic focus information into whole-slide imaging allows automatic high-quality imaging of LBC slides and subsequent biomarker analysis.

Human papillomavirus testing versus repeat cytology for triage of minor cytological cervical lesions

BACKGROUND

Atypical squamous cells of undetermined significance (ASCUS) and low-grade squamous intra-epithelial lesions (LSIL) are minor lesions of the cervical epithelium, detectable by cytological examination of cells collected from the surface of the cervix of a woman.Usually, women with ASCUS and LSIL do not have cervical (pre-) cancer, however a substantial proportion of them do have underlying high-grade cervical intra-epithelial neoplasia (CIN, grade 2 or 3) and so are at increased risk for developing cervical cancer. Therefore, accurate triage of women with ASCUS or LSIL is required to identify those who need further management.This review evaluates two ways to triage women with ASCUS or LSIL: repeating the cytological test, and DNA testing for high-risk types of the human papillomavirus (hrHPV) - the main causal factor of cervical cancer.

OBJECTIVES

Main objective To compare the accuracy of hrHPV testing with the Hybrid Capture 2 (HC2) assay against that of repeat cytology for detection of underlying cervical intraepithelial neoplasia of grade 2 or worse (CIN2+) or grade 3 or worse (CIN3+) in women with ASCUS or LSIL. For the HC2 assay, a positive result was defined as proposed by the manufacturer. For repeat cytology, different cut-offs were used to define positivity: Atypical squamous cells of undetermined significance or worse (ASCUS+), low-grade squamous intra-epithelial lesions or worse (LSIL+) or high-grade squamous intra-epithelial lesions or worse (HSIL+).Secondary objective To assess the accuracy of the HC2 assay to detect CIN2+ or CIN3+ in women with ASCUS or LSIL in a larger group of reports of studies that applied hrHPV testing and the reference standard (coloscopy and biopsy), irrespective whether or not repeat cytology was done.

SEARCH METHODS

We made a comprehensive literature search that included the Cochrane Register of Diagnostic Test Accuracy Studies; the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library), MEDLINE (through PubMed), and EMBASE (last search 6 January 2011). Selected journals likely to contain relevant papers were handsearched from 1992 to 2010 (December). We also searched CERVIX, the bibliographic database of the Unit of Cancer Epidemiology at the Scientific Institute of Public Health (Brussels, Belgium) which contains more than 20,000 references on cervical cancer.More recent searches, up to December 2012, targeted reports on the accuracy of triage of ASCUS or LSIL with other HPV DNA assays, or HPV RNA assays and other molecular markers. These searches will be used for new Cochrane reviews as well as for updates of the current review.

SELECTION CRITERIA

Studies eligible for inclusion in the review had to include: women presenting with a cervical cytology result of ASCUS or LSIL, who had undergone both HC2 testing and repeat cytology, or HC2 testing alone, and were subsequently subjected to reference standard verification with colposcopy and colposcopy-directed biopsies for histologic verification.

DATA COLLECTION AND ANALYSIS

The review authors independently extracted data from the selected studies, and obtained additional data from report authors.Two groups of meta-analyses were performed: group I concerned triage of women with ASCUS, group II concerned women with LSIL. The bivariate model (METADAS-macro in SAS) was used to assess the absolute accuracy of the triage tests in both groups as well as the differences in accuracy between the triage tests.

MAIN RESULTS

The pooled sensitivity of HC2 was significantly higher than that of repeat cytology at cut-off ASCUS+ to detect CIN2+ in both triage of ASCUS and LSIL (relative sensitivity of 1.27 (95% CI 1.16 to 1.39; P value < 0.0001) and 1.23 (95% CI 1.06 to 1.4; P value 0.007), respectively. In ASCUS triage, the pooled specificity of the triage methods did not differ significantly from each other (relative specificity: 0.99 (95% CI 0.97 to 1.03; P value 0.98)). However, the specificity of HC2 was substantially, and significantly, lower than that of repeat cytology in the triage of LSIL (relative specificity: 0.66 (95% CI 0.58 to 0.75) P value < 0.0001).

AUTHORS' CONCLUSIONS

HPV-triage with HC2 can be recommended to triage women with ASCUS because it has higher accuracy (significantly higher sensitivity, and similar specificity) than repeat cytology. When triaging women with LSIL, an HC2 test yields a significantly higher sensitivity, but a significantly lower specificity, compared to a repeat cytology. Therefore, practice recommendations for management of women with LSIL should be balanced, taking local circumstances into account.

[Are vaginal pap smear necessary after total hysterectomy for CIN3?]

The practice of vaginal smears after total hysterectomy should be discussed according to the indication for hysterectomy. We have thus performed a literature review using PubMed medical database with selection of articles presenting a practical interest for clinicians. The practice of vaginal smears after endometrial cancer can be abandoned, but in case of cervical cancer it improves the performance of clinical examination in the early follow-up (in the first 5 years of follow-up) especially in early diagnosis of subclinical recurrence. After this period, the interest of vaginal smears drop drastically and the follow-up is mainly clinical. When hysterectomy is proposed as part of cervical intraepithelial neoplasia (particularly when associated uterine lesions and cervical conization not accessible), the risk of vaginal recurrence of HPV-induced pathology fully justifies an annual monitoring (recurrences or virus-induced lesions are seen up to 25 years after surgery). Finally, after hysterectomy for benign uterine non-HPV-induced, there is no need to propose a systematic follow-up cytology.

Risk of high-grade cervical intraepithelial neoplasia during follow-up in HPV-positive women according to baseline p16-INK4A results: a prospective analysis of a nested substudy of the NTCC randomised controlled trial

BACKGROUND

Immunostaining for p16-INK4A (henceforth p16) is a sensitive and specific method for detection of high-grade cervical intraepithelial neoplasia (CIN) in women infected with human papillomavirus (HPV), but longitudinal data have not been obtained. We investigated the relation between p16 status and risk of CIN during 3 years of follow-up.

METHODS

Women aged 25-60 years were enrolled between June 10, 2003, and Dec 31, 2004, in a multicentre randomised trial comparing HPV testing with cytology. HPV-positive women were referred for colposcopy and, in seven of nine centres, were tested for p16 overexpression by immunostaining. If no CIN was detected, these women were followed up at yearly intervals until clearance of HPV infection. The primary endpoint was histologically confirmed CIN of grade 2 or worse (CIN of grade 2 [CIN2], CIN of grade 3 [CIN3], or invasive cervical cancer) at recruitment or during follow-up. We calculated the absolute and relative risks by p16 status at recruitment. We also calculated the longitudinal sensitivity of p16 testing. Additionally, we assessed the relative sensitivity of an alternative strategy (referral to colposcopy and follow-up of only HPV-positive, p16-positive women) versus conventional cytology in two age groups. Percentages were weighted by the inverse of the tested fraction. The trial in which this study is nested is registered, number ISRCTN81678807.

FINDINGS

Of 1042 HPV-positive women who were tested for p16 with no CIN detected during the first round of screening, 944 (91%) had further HPV tests. 793 (84%) of these 944 were followed up until detection of CIN2 or worse, HPV infection clearance, or for at least 3 years. CIN2 or worse was detected during follow-up in more p16-positive women (31 of 365, 8·8% [95% CI 5·8-11·8]) than in p16-negative women (17 of 579, 3·7% [1·9-5·4]; relative risk [RR] 2·61 [95% CI 1·49-4·59]). RR was higher in women aged 35-60 years at recruitment (3·37 [1·39-8·15]) than in those aged 25-34 years (2·15 [1·00-4·61]), but age was not a significant modifier. CIN3 or worse was detected during follow-up in more p16-positive women (16 of 365, 4·4% [2·3-6·6]) than in p16-negative women (six of 579, 1·3% [0·2-2·3]; RR 3·90 [95% CI 1·57-9·68]). Longitudinal sensitivity of p16 testing for detection of CIN3 or worse during follow-up at all ages was 77·8% (95% CI 63·9-91·6). The relative sensitivity of the alternative strategy compared with conventional cytology was 2·08 (1·13-3·56) in women aged 35-60 years and 2·86 (1·28-5·36) in those aged 25-34 years. HPV-positive, p16-negative women aged 35-60 years had a higher cumulative risk of CIN3 or worse during recruitment or follow-up (2·0%, 95% CI 0·3-3·7) than did HPV-negative women (0·01%, 0-0·04) or those who were cytologically normal (0·04%, 0·02-0·09) at recruitment.

INTERPRETATION

p16 overexpression is a marker for CIN2 or worse or for development of CIN2 or worse within 3 years in HPV-positive women, especially those aged 35-60 years. HPV-positive, p16-positive women need immediate colposcopy and, if the assessment is negative, annual follow-up. Immediate colposcopy can be avoided in HPV-positive, p16-negative women, who can be safely managed with repeat screening after 2-3 year intervals.

FUNDING

European Union; Italian Ministry of Health; Regional Health Administrations of Piemonte, Tuscany, Veneto and Emilia Romagna; and Public Health Agency of Lazio Region.

The role of co-factors in the progression from human papillomavirus infection to cervical cancer

OBJECTIVE

Co-factors for cervical cancer, including oral contraceptive (OC) use, smoking and multiparity have been identified; however, the stage at which they act in cervical carcinogenesis is not clear. We compared established risk factors among women with CIN2 and CIN3 to evaluate the heterogeneity of these factors in precancer and also assessed their role during cervical carcinogenesis.

METHODS

The current analysis included 2783 women with various stages of cervical disease who were enrolled in the Study to Understand Cervical Cancer Early Endpoints and Determinants (SUCCEED) and the Biopsy Study. Associations of co-factors within cervical precancer and at different stages of cervical carcinogenesis were estimated using logistic regression.

RESULTS

Long-term OC use (10+years vs. never: OR=2.42, 95% CI: [1.13-5.15]), multiparity (3+ births vs. nulliparous: OR=1.54 [1.04-2.28]), smoking (ever vs. never: OR=1.95 [1.48-2.58]), and no Pap test in the previous five years (2.05 [1.32-3.17]) were positively associated with CIN3 compared to CIN2. We observed that long-term OC use, parity and smoking were associated with an increased risk of CIN3 compared to <CIN2 (1.97 [1.12-3.46]; 2.23 [1.59-3.11]; 2.60 [2.04-3.30], respectively), whereas associations were not significantly different (OC use, parity) or showed decreased risk (smoking) when comparing cancer to CIN3.

CONCLUSIONS

Differences in established risk factors suggest that CIN3 is a more specific definition of precancer than CIN2. Hormonally-related factors and smoking play a role in the transition from human papillomavirus infection to precancer.