ERCC1 and topoisomerase I expression in small cell lung cancer: prognostic and predictive implications

Small cell lung cancer is the most aggressive lung cancer subtype. The standard treatment approach is based on cisplatin regimens. Although response rates to treatment are approximately 60-80%, the median survival is still very poor. Excision repair cross complementation group 1 (ERCC1) is an enzyme that removes cisplatin-induced DNA adducts and has been related with prognosis and cisplatin response. Topotecan is the standard treatment as second-line therapy and it is an inhibitor of topoisomerase I (TOP I). We selected 76 patients with small cell lung (SCLC) to analyze the ERCC1 and TOP I mRNA expression. ERCC1 was studied both by quantitative PCR and immunohistochemistry. A significant association was found between the inmunohistochemistry expression of ERCC1 and the lack of platinum response (p=0.001). Moreover, low levels of TOP I RNA were shown to be linked to cisplatin response (p=0.002). In the survival analysis, a significant correlation between a better PFS with a low TOP I RNA expression as well as a negative ERCC1 inmunostaining were found, in both cases with a significant p-value (p=0.02 and 0.009, respectively). In summary, our results suggest the use of ERCC1 immunohistochemistry and TOP I mRNA analysis to predict cisplatin response and prognosis in SCLC patients.