Modeling post-treatment development of cervical carcinoma: exophytic or endophytic – does it matter?

In this study, we use a combination of smoothing nonparametric and parametric methods to estimate the hazard function for the disease-free interval from clinical data on patients with carcinoma of the cervix uteri. Three estimation procedures were used for estimating the hazard rate from the data: the life table estimator, a kernel counterpart of the Nelson–Aalen estimator, and a parametric estimator based on a mechanistic model of tumor recurrence. The parametric estimate appears to be in good agreement with its nonparametric counterparts suggesting a bimodal shape of the underlying hazard function. The observed two-component structure of the hazard function can be attributed to a certain heterogeneity of ‘malignant potential’ remaining in treated tumors. Exophytic and endophytic carcinomas of the cervix uteri show dissimilar patterns of this heterogeneity and its evolution with the time elapsed after treatment. The results of parametric inference suggest that exophytic and endophytic recurrent tumors differ as to quantitative characteristics of a slowly evolving subpopulation of clonogenic tumor cells.