Estimation of tumor stage and lymph node status in patients with colorectal adenocarcinoma using probabilistic neural networks and logistic regression

Staging colorectal adenocarcinoma on the basis of biopsy specimens could id entify patients who might benefit from neoadjuvant therapy without undergoi ng resection first. In this study, we evaluated the ability of artificial n eural networks with genetic algorithms and multivariate logistic regression to predict the stage of 99 patients with primary colorectal adenocarcinoma by analyzing age, tumor grade, and immunoreactivity to p53 and bcl-2 with use of endoscopically obtained biopsy specimens. We correlated results with regional lymph node status and tumor stage, identified in subsequent colec tomy specimens. bcl-2 and p53 protein expression were demonstrated by immun ohistochemical methods, using formalin-fixed, paraffin-embedded biopsy tiss ues. Tumor grade was evaluated in hematoxylin- and eosin-stained sections. Patients were divided into training (n = 75) and testing cases (n = 24). Se veral probabilistic neural networks with genetic algorithm models were trai ned, using the four prognostic features as input neurons and regional lymph node status or stage as output neurons. Data were analyzed with univariate statistics and multivariate logistic regression. The cases were divided in to training (n = 40) and testing (n = 59). The best two models classified c orrectly the lymph node status of 20 of 24 test patients (specificity, 80%; sensitivity, 85%; positive predictive value, 86%) and the tumor stage of 2 1 of 24 test patients (specificity, 82%; sensitivity, 92%; positive predict ive value, 85%), respectively. Tumor grade and p53 protein were statistical ly significant (P <.05) by analysis of variance for lymph node status and t umor stage. Logistic regression models with these two independent variables correctly estimated the probability of lymph node metastases in 44 of 59 t est cases and the tumor stage of 43 of 59 test cases, respectively. Results indicated the usefulness of probabilistic neural networks in the populatio n studied, but the findings should be validated with large groups of patien ts.