Immunohistochemical detection of mutant p53 protein in small-cell lung cancer: relationship to treatment outcome

We investigated the expression of mutant p53 proteins in small-cell lung cancer (SCLC) immunohistochemically, by identification of stabilized mutant p53 proteins with a much longer half-life than the wild-type protein. Of 103 tumor specimens obtained by transbronchial tumor biopsy for histologic diagnosis, 52 (50%) showed positive staining for p53 protein with a p53 monoclonal antibody, DO-1. Positive staining for p53 protein was not correlated with age, sex, performance status, lifetime cigarette consumption, serum concentration of neuron-specific enolase and extent of disease. Complete response rates in patients with a mutant p53 protein-positive tumor were significantly lower than those in p53-negative patients (25% versus 59%; P = 0.0005. by chi-square rest). Similarly. survival periods in patients with a mutant p53 protein-positive turner were significantly shorter than those in mutant p53-protein-negative patients (10.8 months versus 20.6 months: P = 0.0001, by generalized Wilcoxon test). Multivariate analysis using Cox's proportional hazards model revealed that the presence of mutant p53 protein is an independent factor associated with differences in overall survival (hazards ratio = 2.72. 95% confidence interval, 1.71-4.34; P = 0.0001). These observations suggest that the expression of mutant p53 proteins in SCLC may be an important factor predicting pool prognosis. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.