My dad has diffuse large b-cell lymphoma stage 4 and he had a clean pet scan in November 2011. Now only two months later after his last treatment and petscan the cancer is there and spread across his throat and chest. I am so sad and terrified. He has to go to a different hospital to start a different intense chemo treatment that lasts 4 days in the hospital(I don't know what the treatment is called yet. I just don't understand how doctors could say it was gone and now its back. Has anyone had this happen where rchop didn't work and another type of chemo responded.Please pray for my dad! P.s. him throwing up the other day was the stomach flu. My kids just got over it too. Lasts a day or two.