Well, fatigue definitely sets in. I don't understand all the mechanisms for how the radiation causes fatigue but believe me it does.

Likely you won't notice much for the first couple of weeks. If they're radiating the mouth you will begin to notice soreness in the mouth which will become worse over the course of Tx. Most people having Rad to the mouth area will end up on pain meds for the pain and eating can become very difficult if not impossible. Many people, myself included, end up getting a PEG tube in their stomach to pump in liquid nutrition. My first and second round of treatment, that's how I ate through treatment - pumping Insure through my PEG tube once I could no longer eat by mouth.

You can also develop burns on the skin from the radiation. My first round I didn't experience this as badly as the second round. First round I just had what was like a sunburn on my neck. The second round, by the end of the 7 weeks of IMRT I had open, oozing burn wounds on a good portion of the right side of my neck. These continued for a good month after treatment ended.

What most will tell you is that the symptoms radiation causes will continue beyond when Radation ends. The average seems to be about 4-6 weeks after Tx until they start to subside - that's about how long it was for me. You get so excited that radiation is ending, and it catches a lot of people off guard that the symptoms don't immediately go away upon finishing. Many people say it's the "gift that keeps on giving".

It can really vary depending on where and how much radiation you're getting to each area of the mouth, neck, etc. You should be able to find plenty of info on this site about the kinds of symptoms you can expect beyond what I've explained.

-Steve