Hi, Debo -
"Maria, you mention 'staging' - what is this, and why be specifically careful about asking about it?"
Cheryl answered about staging for me above. If is stage four, people tend to flip out a bit (I know I did) and it is hard to say. Many of us caregivers and survivors use the T (tumor) N (nodes) M (distant mets) staging description - but there are a lot of stage fours that are doing really well.
" Also, is there a general rule of thumb of when people in chemo/radio treatment feel most awful?"
If treatment will be the 3 big bag cisplatin, the days of the chemo and the days following it will be pretty sucky. Other schedules and chemo have there on special miseries - but the doctors have come a long way in their ability to control the side effects.
The radiation is cumulative, as Cheryl noted.
"Is there any rule of thumb about being present or staying away?"
This will depend on the specific chemo as to how careful you have to be; some impact the immune system more than others. Common sense is in effect! You don't want you Dad getting sick and having the treatment delayed!
Maria