Is Lonsurf a "last option"

To make this short, my dad was diagnosed with metastatic rectal cancer that had spread to his liver with a few Mets on his right lung in July of 2019 at age 59.

Fast forward to the end of 2020 lung Mets gone, resection of cancer in rectem done and gone. Liver tumors almost non existence and blood work was at like "7" for whatever they look for, down from over 300.

April of 2021 numbers back over 300. All tumors in liver only. Dad was given 1 year at most. It is unoprabal because it will spread everywhere according to his Dr. ( we have willing blood match family doners)

Now end of July 2022 tumors in liver stopped responding to traditional chemo. He is supposed to start Lonsurf next week FIVE times a day ( from reading this seems like way more then normal) they called it "extreme chemo" and said it's it.... that's all there is.

My question is is that really all there is? I still don't understand why the recession was ok to do in the rectum but not the liver. I know there is no magic to be had but he wants to live he's only 62 years old. My mom passed away at age 44 and I am being selfish but I don't want to lose my dad too. I want to do everything I can to help him.

If he didn't want to fight I would support his decision but he does and I want to fight for him.