Natural History of Cervical Dysplasia

Spontaneous evolution of intraepithelial lesions according to the grade and type of the implicated human papillomavirus (HPV)

Because of the fact that any meaningful classification should bear a close relationship to the biological behavior of the lesions, the usefulness of all new classifications of cervical precancer lesions can only be established by well controlled prospective follow-up studies. However, several methodological and conceptual problems are encountered in the natural history studies conducted during the past several decades. While reviewing the available prospective follow-up studies on cervical intraepithelial neoplasia (CIN), Ostör (1993) found 3529 cases of CIN 1, of which 57% showed regression, persistence was found in 32%, progression to CIN III in 11%, and progression to invasive cancer in 1% of cases. The corresponding figures for CIN II were 43%, 35%, 22%, and 5%, respectively. The recognition of the association between human papillomavirus (HPV) and CIN has further complicated the assessment of the natural history of cervical precancer lesions. Results from the early prospective follow-up studies are remarkably consistent, however. Progression from HPV-NCIN (i.e., koilocytosis without CIN) to CIN I or greater was reported for 18 (8%) of 232 women followed by Syrjänen et al. for an average of 25 months, for 26 (8%) of 314 women followed by de Brux et al. (1981) for 15 to 18 months, and for 113 (13%) of 846 women followed for up to six years by Mitchell et al. During a 42-month follow-up period, 10% progression rate was found in 1269 women with HPV-CIN I, and in 17% of 762 women with HPV-CIN II by de Brux et al. (1983). The spontaneous regression rates were 53% and 39% in these cohorts, respectively. This is fully consonant with our experience from an almost 14-year follow-up of 530 women in Kuopio, where the spontaneous regression rate seems to increase in parallel with the extent of the follow-up time, currently being 66.7% for HPV-NCIN and 55.7% for HPV-CIN I. The figures for progression are 6.3% and 14.2%, respectively. It is obvious that the probability of a cervical precancer lesion to progress into an invasive disease increases with the severity of the atypia. Another distinct prognostic factor is HPV type, HPV 16 lesions possessing a significantly higher risk for progression than infections by other HPV types. The follow-up data also indicate, however, that even the high grade lesions may spontaneously regress, which should have important implications in therapy. The continuous problem still remains; these natural history observations only apply to a large series of women but are of little help in predicting the disease outcome in individual women.

Surrogate endpoint biomarkers for cervical cancer chemopreventive trials

Cervical intraepithelial neoplasia (CIN) represents a spectrum of epithelial changes that provide an excellent model for developing chemopreventive interventions for cervical cancer. Possible drug effect surrogate endpoint biomarkers are dependent on the agent under investigation. Published and preliminary clinical reports suggest retinoids and carotenoids are effective chemopreventive agents for CIN. Determination of plasma and tissue pharmacology of these agents and their metabolites could serve as drug effect intermediate endpoints. In addition, retinoic acid receptors could serve a both drug and biological effect intermediate endpoints. Possible biological effect surrogate endpoint biomarkers include cytomorphological parameters, proliferation markers, genomic markers, regulatory markers, and differentiation. Given the demonstrated causality of human papillomavirus (HPV) for cervical cancer, establishing the relationship to HPV will be an essential component of any biological intermediate endpoint biomarker. The pathologic effect surrogate endpoint biomarker for cervical cancer is CIN, used clinically for years. The desired effect for chemopreventive trials is complete regression or prevention progression. In planning chemoprevention trials, investigators need to consider spontaneous regression rates, the subjective nature of detecting CIN, and the impact of biopsy on regression. If intermediate endpoint biomarkers that met the above criteria were available for cervical cancer, then new chemopreventive agents could be rapidly explored. The efficacy of these new agents could be determined with a moderate number of subjects exposed to minimal risk over an acceptable amount of time. The impacts on health care for women would be significant.

Progressive potential of mild cervical atypia: prospective cytological, colposcopic, and virological study

A prospective study of 100 women with cytological and colposcopic evidence of mild cervical atypia consistent with cervical intraepithelial neoplasia (CIN) grade I was started in October, 1983. 26% of early preinvasive cervical lesions progressed to histologically proven CIN III. Spontaneous regression of mild cervical atypia occurred in only 11 cases, and in 4 of these CIN recurred. The overall prevalence of human papillomavirus type 16 (HPV 16) in the study group, detected by filter DNA-DNA hybridisation of a cervical cytological specimen, was 39%. However, 22 of the 26 (85%) cases of progressive disease were positive for HPV 16. Detection of HPV 16 may be a non-invasive way of identifying women at high risk of rapid progression of mild cervical atypia to CIN III.

Papillomavirus infection and squamous neoplasia of the cervix

In the past, the lack of a tissue culture system or an animal model suitable for inducing HPV lesions precluded the study of the role of PV in human disease. The development of a genus-specific cross reacting PV antiserum and molecular hybridization techniques now enables pathologists and molecular virologists to assay tissues for the presence of PV structural antigens and DNA sequences using highly specific and sensitive PV probes. The data that has been generated with these new research tools has far reaching implications. For example, the multifocality of squamous carcinoma of the vulva, vagina and cervix together with their similar histology, epidemiology and relationship to precursor lesions suggests that all of these neoplasms as well as related tumors in males may be caused by HPV. Since the immunoperoxidase technique using the PV antiserum can be performed on formalin-fixed paraffin-embedded tissue, systematic evaluation of these lesions can be done retrospectively. After identifying PV-associated lesions by the immunocytochemical method, prospective studies can be undertaken utilizing molecular hybridization in an effort to detect PV-DNA sequences and thereby to more clearly define the role of HPV in squamous neoplasia of the female genital tract.

Cervical wart virus infection, intraepithelial neoplasia and carcinoma; an immunohistological study using a panel of monoclonal antibodies

The pattern of epithelial antigen expression has been examined in normal and disordered cervical squamous epithelium using immunohistological methods and a range of monoclonal antibodies. It was demonstrated that wart virus infection (WVI) is associated with disordered staining for a keratin-associated component and for HLA-DR antigen. Furthermore, wart-infected epithelium shows strong labelling for carcinoembryonic antigen (CEA) and for human milk fat globule antigens 1 and 2 (HMFG1 and 2). In addition these antigens (CEA, HMFG1 and 2) are also expressed in mixed WVI and cervical intraepithelial neoplasia (CIN), CIN III and in carcinoma. While these findings do not allow immunohistological discrimination between non-neoplastic and neoplastic cervical epithelia, they do provide support for the view that cellular proliferation of the type induced by papilloma virus may represent an initiator stage in the process of neoplastic transformation.

On the nature of the deep cellular disturbances in human-papilloma-virus infection of the squamous cervical epithelium

In the squamous epithelium of the cervix, disturbed deep cells, usually regarded as dysplastic, often underlie superficial koilocytes. Recognition of koilocytosis as a cytopathic effect of human papilloma virus (HPV) prompts reconsideration of the state of the deep cells, which could be non-dysplastic or dysplastic. In the dysplastic states HPV could be non-causative or causative. For dysplastic causation by HPV, a cell-differentiation hypothesis reconciles the coexistence in the epithelium of a permissive HPV infection of the superficial layers (koilocytosis) and a non-permissive cellular infection of the deep layers, which may undergo transformation to dysplasia.