Survival Analysis of Gene Expression

Cox proportional hazards regression analysis was made for each gene separately. In this, each possible cutoff value was examined between the lower and upper quartiles, and False-Discovery Rate using the Benjamini-Hochberg method was computed to correct for multiple hypothesis testing. The survival analysis was performed for relapse-free survival (RFS). Breast cancer specific survival was not used because almost all studies published OS and/or RFS only. In case of identical p values the strongest hazard rate was identified. The results for the best performing cutoff were exported for each gene in a separate database, and these were used to generate Kaplan-Meier plots to visualize correlation between gene expression and survival.