X-rays
I reckon that my radiotherapy treatment was about the equivalent of 10,000 normal medical X-rays - I was "allowed" a dose of 2 Grays (~200 rad) per day over 7 5-day weeks. Since these were X-rays, that's also 200 Rem per day. Total dose, 70 Grays, or 7000 Rem.
I haven't grown a second head (yet) but I do have to go back for regular checkups to make sure that I neither have a recurrence of my previous tunour nor does anything new take off as a result of this radiation dose.
It also looks like I can't get a job in the nuclear industry for a few years. I've already exceeded my 5-year dose limit! (Maybe my lifetime limit?)