I had 37 sessions of pelvic radiotherapy (for prostate cancer) spread over 7½ weeks at 5 days per week. I was already feeling tired from 10 sessions of maximum-dose chemotherapy, so the radiotherapy certainly didn't help when it came to tiredness. However, apart from that, I felt as fit as a fiddle throughout and certainly perfectly fit to drive.
As it's pelvic radiotherapy that's being referred to here, it might be relevant to mention that the only slight inconveniences for me (apart from having to drive to and from the hospital 37 times) related to the need to turn up to the hospital with a full bladder but with an empty bowel. I had to use a (very fast acting!) enema about an hour before the treatment and then drink half a litre of water
As a result of that, I was busting for a pee while waiting for, and during, the treatment. (I later managed to get that changed to about 420ml of water, 50 minutes before the radiotherapy session, and things were then a lot easier for me in that respect).
The actual sessions were an absolute doddle. All I had to do was to partially slip my trousers down and hop onto the couch. A paper towel (or something very similar to one anyway) was then used to protect my modesty when I slipped my underpants down. Each treatment only lasted a couple of minutes and then, after dressing, I was free to go home (or, more accurately, to dash to the loo for a pee!)