Plot: how to change the breaks?

I'm plotting a survival curve with the survival library, and I haven't found any way to change the breaks range.

For example:

library(survival)
temps <- c(5,15,25,30,18,16,38,40,40,40,40,40,40,40,40,40)
deces <- c(1,0,1,1,1,0,1,1,0,0,0,0,0,0,0,0)
plot(survfit(Surv(temps,deces)~1))    

Gives us this plot:

If I want, I can change the range of the whole axis with xlim=c(), the scale of abscissa numbers with xscale.

But the x breaks ranges will always stay at every 5 or 10 units (10,20,30,40). It's impossible to change them to 12 for example, as I want (12, 24,36,...) because they should represent months.

Is this possible to change them? Or do I have to use the survminer library?