Hey Sheryn
It's a really shitty thing - but if the cancer is going to recur, it typically does right away - ie in the first year. Each year after treatment means less likelihood of recurrence.
I could never wrap my head around the math, at one point after treatment and a clear PET scan, a doctor said to me "your odds are about 95%+ that you've beaten the disease"
Then in the first year of review another doctor said "in the first year, with your staging, you have about a 30% chance of recurrence".
So it beats me. Ignoring probability, it does happen, and the later your staging, the more likely. I think my disease was more advanced than your dad's, but I just got lucky (touch wood)
Things I've heard about treatment options:
I was told that if I have recurrence, radiation was not a possible pathway.
I was told that surgery was the only option, but after radiation my H&N cancer will have shrunk to a size that surgery becomes viable.
I was told that the complications and impairment from a H&N surgery can be pretty devastating, they have to break, remove and rebuild your jaw, important nerves can be severed, all kinds of nasty stuff.
BUT, I've also heard of cases where people have had supplemental radiation when the cancer recurred in a nearby area.
I was told that for tonsil cancer, supplemental chemotherapy is useless, at treatment it only increased the success rate by 2% (for me), the main gun brought to the fight was the radiation. The radiation oncologist said that if you suffer a recurrence, more rads is unlikely, more chemo is useless, surgery is the only pathway, aside from new emerging immunotherapies.
On immunotherapy - I've also heard of some exciting successes -- my step father was in late stage metastasised cancer - lungs, pancreas, basically all over .. he was in palliative care with weeks to live. He began an immunotherapy trial and about 8 weeks later they were cautiously using words like 'remission'. He still ended up dying, but he got an extra couple of years. (Don't let anecdote colour your expectations though, just suggesting it's worth looking into and asking all doctors)
As a cancer sufferer, I've had to prepare for death, I've had to look that in the face, and in my experience, not shying away from it is the best approach. I hope your dad survives, and I wish you the best - but given the seriousness of the situation, make sure that you do and say anything that needs to be done & said, and enjoy what time remains available. (None of us know when we're due to shuffle off, so that applies equally to everybody, I guess)
I reckon a recurrence that early post treatment sounds pretty grim, and I'd suggest leaning heavily into it - interrogating all the doctors on every viable treatment pathway and it's chances of success or lengthening his life. (Then make an informed choice)
