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

Caregiver/advocate to Husband Kris age 59@ diagnosis
DX Dec '10 SCC BOT T4aN2bM0 HPV+ve.Cisplatin x3 35 IMRT.
PET 6/11 clear.
R) level 2-4 neck dissection 8/1/11 to remove residual node - necrotic with NED
Feb '12 Ca back.. 3/8/12 total glossectomy/laryngectomy/bilat neck dissection/partial pharyngectomy etc. clear margins. All nodes negative for disease. PEG in.
March 2017 - 5 years disease free. Woohoo!