Increasing size of lines in ggplot mean cumulative function plot

I am using the reReg package to create mean cumulative function plots. but I am unable to change the size of lines inside the plot.

is there anyway to increase the line width?

library(reReg)
data(readmission, package = "frailtypack")
readmission <- subset(readmission, !(id %in% c(60, 109, 280)))
mcf0 <- mcf(Recur(t.start %2% t.stop, id, event, death) ~ sex, data = readmission)
p<- plot(mcf0, conf.int = TRUE)

p + theme_bw(base_size = 20)

Thanks for reading

You could use ggplot_build to change the linewidth in each layer with lapply like this (I used big linewidth to show result):

library(reReg)
library(ggplot2)
library(frailtypack)
data(readmission, package = "frailtypack")
readmission <- subset(readmission, !(id %in% c(60, 109, 280)))
mcf0 <- mcf(Recur(t.start %2% t.stop, id, event, death) ~ sex, data = readmission)
p <- plot(mcf0, conf.int = TRUE) + theme_bw(base_size = 20) 

q <- ggplot_build(p)

q$data = lapply(q$data, \(x) {
  x$linewidth = 3
  x
})

q <- ggplot_gtable(q)
plot(q)

^{Created on 2023-04-06 with reprex v2.0.2}

Different linewidth:

library(reReg)
library(ggplot2)
library(frailtypack)

p <- plot(mcf0, conf.int = TRUE) + theme_bw(base_size = 20) 

q <- ggplot_build(p)

q$data = lapply(q$data, \(x) {
  x$linewidth = 1
  x
})

q <- ggplot_gtable(q)
plot(q)

^{Created on 2023-04-06 with reprex v2.0.2}