Yes the 400 character limit still applies. Some members have longer signatures before the limit was put in place will have to make em shorter the next time they try to edit theirs.
Your signature has a lot of unneeded stuff.
Since you finished radiation there's no need to mention: Started radiation treatment on 5th Dec, to continue until 24 Jan. 08.
Also no need to mention "next PSA on 30th April" since you've already done that too.