In situ hybridization for human papillomavirus as a method of predicting the evolution of cervical intraepithelial neoplasia

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.