Anyone have knowledge of rare cancer fetal adenocarcinoma

My husband has been diagnosed with fetal adenocarcinoma, a rare form of lung cancer that has spread to his brain, spleen and pelvic bone. He's had brain surgery to remove the tumours and has now been advised he has about 6 months to live without treatment or 12 to 18 months with quite aggressive treatment which may cause some serious issues. We have to decide quality or quantity, as so many of us with cancer have to do.. thoughts please, would be so welcome 🙏