Please check on you tube for pretension by professor Zajicek on you tube and on his site (what is cancer). I attach one quote but you may want to see it yourself "There is a disease called pernicious anemia that illustrates how a tumor might be protective. It is triggered by a "carcinogen" preventing the entry of vitamin B12 into the body. During its pre-clinical phase, that lasts about two years, the patient is healthy. The clinical phase starts with anemia and "paraneoplasia", known as combined degeneration of the spinal cord and brain. The bone marrow displays "neoplastic" features, e.g., hyperplasia, maturation arrest, and ineffective erythropoiesis, that were regarded in the past as "pseudo-leukemia" (21). These are protective means by the bone marrow that keep the patient alive. With time deficiency deepens more and more until reaching the state of decompensation whereupon the patient dies."

There is a simple B12 deficiency anemia and true pernicious anemia. So you could have been suffering from either.