How can dr tell if cancer has returned after auto sct if blood work is off for 6-12 months after a transplant. What do they look for?

Depends. This depends on the type of cancer that required a stem cell transplant. Different cancers are tested for differently. For instance, leukemia can be looked for by blood testing, bone marrow testing. Lymphoma can be looked for by physical examination, ct scanning, pet scanning. Myeloma is evaluated by blood testing and/or marrow testing.