Diana, to some extent,I had similar experience as your dad when I had finished 4 rounds of chemo plus 5 weeks of radiation (concurrent treatment). My WBC count was very low, high fever (over 102), weight loss, dehydration, mouth sore,... many more symptoms you can name. I was admitted to hospital on 10/12/01 for blood transfusion and antibiotic to combat pneumonia. I did not have my radiation suspended since my high fever usually disappeared early in the morning and when the nurse took my temperature, it was Ok for the radiation. So from 1/11/01 to 19/12/01, I had radiation every day except Saturday and Sunday and in the last two weeks, I had it twice a day. A very tough road for me but I managed to go through it. A delay of treatment may not be a bad thing for your dad to take a break but if the treatment is suspended for a long time, it may affect the effect but the team of doctors looking after your dad should know the best. By the way, I did not experience heart problem or short of breath mentioned in the latter half of your post and I don't think it is normal. Everyone is different and I only share my own view which is by no means professional.

Karen stage 4 tonsil cancer diagnosed in 9/01.