germ cell tumor prognosis

My 5 year old son was diagnosed with stage IV germ cell tumor.  It has spread to his lungs. His main non-gonadal tumor is located in his pelvis between his bladded and his spine. The dr.s gave him about a 70% recovery chance, but on Harvard Medical School's website they said non-gonadal germ cell tumors have about a 70% chance, all except those located in the pelvis which I believe they said had a 28% chance, and after they have spread only 4%! I'm having trouble finding information specific to non-gonadal pelvically located germ cell tumors in young boys. His dr.s are still sure they are correct but have been unable to provide me with any specific written proof to back up their beliefs. I am very worried that they are mistaken and that my son has only a 4% chance of survival. Does anyone have any experience with this specific issue?

[Enoch Choi]

I'm not an oncologist, but searching for information about extragonadal pediatric germ cell tumors led me to this site which may have pertinent information:

http://www.cancer.gov/cancertopics/pdq/treatment/extracranial-germ-cell/HealthProfessional/page10

Enoch Choi, MD