14-3-3σ Methylation in Pretreatment Serum Circulating DNA of Cisplatin-Plus-Gemcitabine-Treated Advanced Non–Small-Cell Lung Cancer Patients Predicts Survival: The Spanish Lung Cancer Group

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Abstract
Purpose Survival in patients with advanced non–small-cell lung cancer (NSCLC) who are treated with platinum-based chemotherapy is rather variable. Methylation-dependent transcriptional silencing of 14-3-3σ, a major G2-M checkpoint control gene, could be a predictor of longer survival. Patients and Methods A sensitive methylation-specific polymerase chain reaction assay was used to evaluate 14-3-3σ methylation status in pretreatment serum DNA obtained from 115 cisplatin-plus-gemcitabine–treated advanced NSCLC patients. Results 14-3-3σ methylation was observed in all histologic types of 39 patients (34%). After a median follow-up of 9.8 months, median survival was significantly longer in the methylation-positive group (15.1 v 9.8 months; P = .004). Median time to progression was 8 months in the methylation-positive group and 6.3 months in the methylation-negative group (log-rank test, P = .027). A multivariate Cox regression model identified only 14-3-3σ methylation status and Eastern Cooperative Oncology Group performance status as independent prognostic factors for survival. In an exploratory analysis, median survival for 22 methylation-positive responders has not been reached, whereas survival was 11.3 months for 29 methylation-negative responders (P = .001). Conclusion Methylation of 14-3-3σ is a new independent prognostic factor for survival in NSCLC patients receiving platinum-based chemotherapy. It can be reliably and conveniently detected in the serum, thus obviating the need for tumor tissue analysis.