Hi, I choose two genes and perform survival analysis on these two genes. The equation here is coxph(Surv(time,censor) ~ exprs1+exprs2)”, where exprs1 and exprs2 are the TMM normalized expression value for gene1 and gene2. Time is survival time (for dead patients) or last follow up time (for alive patients), censor is dead or alive for each patient.
You can see this plot by clicking this url (https://pan.baidu.com/s/1BDrmHAuAmW6fiyfsSJcHyw).
You can see that the group with low expression of both gene1 and gene2 is the worst. And the group with high expression of both gene1 and gene2 is the best (using the median of expression value as cutoff). However, group with high expression of gene2 and low expression of gene1 is between the lines of the worst and the best (group with high expression of gene1 and low expression of gene2 is the same).
Here is my question. Can I say that there is an interaction between these two genes on survival analysis? If the answer is yes, I can change my equation to coxph(Surv(time,censor) ~ exprs1*exprs2) to see the interaction?