Hey Ceazar- I had Erbitux along with my rads. It was my understanding that they like to do a loading dose before radiation starts and then weekly through the remainder of radiation - I'd be curious as to why they're thinking of adding it now after your dad's had a month or rads already.
Anyways - it specifically targets squamous cells so it's different than most other chemo's. The expected side effects are adolescent like acne and rashes to the chest and back. I had a particularly strong response to the drug - very painful and swollen chin, face, lips and it was so red it was almost purple. It was hard to go out in public - I was not being self-concious - it was very noticable. I remember thinking for a while during treatment that no one would know there was something really wrong with me if it weren't for that damned Erbitux rash! So- long story short - the side effects sucked but were not horrible. I would do it again. My face totally healed up with in 2 weeks of the end of treatment - now if my hair would just grow back(not Erbitux's fault - taxotere did that!)
Good luck to you and your Dad!