Center the plot title in ggsurvplot

Question

I'm struggling with getting my plot title to the center using ggsurvplot...

I've seen some posts mentioning something like xxxx$plot + theme(....) but this solution does not seem to work for me.

Here's my code, maybe you can see what I'm missing:

surv_object_CA19.9 <- Surv(time = data_OS$OS_Days / 30, event = data_OS$Status.Death)
CA19.9_surv_fit <- survfit(surv_object_CA19.9 ~ CA19.9.initial_status, data = data_OS)

CA19.9_OS <- ggsurvplot(CA19.9_surv_fit, data = data_OS, pval = TRUE, xlab = "Time [Months]", 
           ylab = "Overall survival", risk.table = TRUE, legend.title = "", 
           risk.table.col. = "strata", risk.table.y.text = FALSE, surv.scale = "percent", 
           break.x.by = 6, xlim = c(0, 60), legend.labs = c("Pathological", "Normal"), 
           title = "Overall survival for patients with initially pathological or normal CA19-9 values", 
           CA19.9_OS$plot + theme(plot.title = element_text(hjust = 0.5)))

Thank you for any help! I'm still new to R and not particularly a friend of it yet, so any tips are highly appreciated!

Answer 1

One relatively easy solution is to define your own custom theme based off of the theme that is used in ggsurvplot(). Looking at the documentation for the function shows us that it is applying via ggtheme= the theme theme_survminer(). We can create a custom function that uses %+replace% to overwrite one of the theme elements of interest from theme_survminer():

custom_theme <- function() {
  theme_survminer() %+replace%
    theme(
      plot.title=element_text(hjust=0.5)
    )
}

Then, you can use that theme by association with the ggtheme= argument of ggsurvplot():

library(ggplot2)
library(survminer)

require("survival")
fit<- survfit(Surv(time, status) ~ sex, data = lung)
ggsurvplot(fit, data = lung, title='Awesome Plot Title', ggtheme=custom_theme())