Background: Small cell lung cancer (SCLC) is a very aggressive disease, with poor survival rates despite standard treatment with combination chemotherapy with or without radiotherapy. Further insights into the molecular biology of this malignant tumour are needed to improve the therapeutic approaches and outcome. KIT protein is expressed in SCLC, and its kinase activity has been implicated in the pathophysiology of many tumours, including SCLC. The purpose of this study was to evaluate the prevalence of KIT expression in patients with SCLC and its prognostic value.
Methods: We performed an inmunohistochemical analysis of 204 SCLC samples to determine KIT protein expression. The relationship between KIT expression and clinicopathological parameters was evaluated. Univariate and multivariate analyses were performed to define its prognostic significance.
Results: KIT expression was observed in 149 of 204 tumour tissues (73%). KIT expression was associated with advanced disease and with decreased incidence of bone metastases. No significant differences were observed for time to disease progression (TTP) (9.1% versus 6.2% at 3 years, p=0.6) or overall survival (OS) (10.7% versus 6.9% at 3 years, p=0.37) among patients with KIT positive versus negative tumours, respectively. Multivariate analysis showed that sex, tumour stage, albumin levels and response to therapy were the only independent predictors for survival.
Conclusion: KIT protein is expressed in a high percentage of SCLC tumours. In our study population, however, the expression of KIT had no significant impact on survival.