Hello Shivani, I'm so sorry to hear this news of your Father.
My husbands base of tongue cancer was not cured by radiation and chemo.
He then had extensive surgery to remove the tumour and reconstruct his Oropharynx. That was 2 1/2 years ago. He is well.
As Paul says , if you give us more information on where his tumour is , those who have had a similar experience can tell you their story.
There is always hope.
Tammy