Hi Neelesh, it is quite difficult to advise as the treatment options available in the UK may not be the same in India or might be available but extremely expensive. As your grandad had his testicles removed in 2004 it seeems quite likely that they were already aware then that his cancer had spread outside the prostate so he has done brilliantly to still be here 12 years later.
Honvan is not used in the UK but it is an oestrogen that is given to men when other hormone treatments don't work any more.Those hormone treatments are no good for your grandad because he already has no testosterone. In the UK the next step would probably be chemotherapy to try to extend his life a bit.
I hope you can find some information about chemo in India?