Hematopoietic Stem Cell Transplantation; Multiple Myeloma/therapy; Adult; Age Factors; Antigens, CD34/therapeutic use; Antineoplastic Combined Chemotherapy Protocols/therapeutic use; Antineoplastic Combined Chemotherapy Protocols/toxicity; Blood Component Removal; Cyclophosphamide/administration & dosage; Cyclophosphamide/toxicity; Cytarabine/administration & dosage; Cytarabine/toxicity; Dexamethasone/administration & dosage; Dexamethasone/toxicity; Disease-Free Survival; Erythrocyte Transfusion; Evaluation Studies as Topic; Follow-Up Studies; Granulocyte Colony-Stimulating Factor/administration & dosage; Humans; Infections/etiology; Italy; Male; Middle Aged; Multiple Myeloma/complications; Myeloablative Agonists/therapeutic use; Myeloablative Agonists/toxicity; Neutrophils; Platelet Count; Prognosis; Retrospective Studies; Risk Factors; Stem Cells; Survival Rate; Transplantation, Autologous; Treatment Outcome; Vincristine/administration & dosage; Vincristine/toxicity