Maintenance Treatment of Multiple Myeloma (MM) After Autologous Peripheral Blood Transplant (PBSCT) Using Polyethylene Glycol alpha2B Interpheron (PEG-INTRON)

Inclusion Criteria: * Patients ≤ 65 years old diagnosed with multiple myeloma in stage II or III of Durie-Salmon staging. * Patients who have achieved a complete response, partial after a myelosuppressive chemotherapy treatment followed by infusion of peripheral blood progenitor cells as first-line treatment. The criteria used to define the complete or partial response are the EBMT, ABMTR IBMTR and set out in the criteria paper of Bladé J, Samson D, Reece D, et al 1998 * Subjects must have a Karnofsky performance status ≥ 60% at the time of joining the program. * Subjects must have adequate renal and hepatic function, defined as \<2 times the upper limit of normal laboratory. * Subjects must have adequate hematologic function, defined as: platelets\> 50,000/μl, ≥Hemoglobin 9.0 g/dl, total leukocyte account\> 2.000/μl * No history of any cancer within the past 5 years except squamous cell carcinoma or basal cell skin or cervical carcinoma in stage I or in situ. * No history of hypersensitivity to interferon alfa or any other part of the injection. * No severe clotting disorders, thrombophlebitis or pulmonary embolism, or decompensated liver disease. * Pregnant or lactating at the time of diagnosis can not participate in this therapeutic program. During the same, men and women participants should not conceive children. Also, women who become pregnant will be withdrawn from the protocol. * Obtaining informed consent. Exclusion Criteria: * Patients \> 65 years old. * Patients with multiple myeloma stage I of Durie-Salmon staging system. * Patients who have not achieved a complete or partial response after a myelosuppressive chemotherapy regimen followed by infusion of progenitor cells from peripheral blood autologous treatment of any kind is allowed intensification of chemotherapy and pretransplant conditioning regimen. The criteria used to define the complete or partial response are the EBMT, ABMTR IBMTR and set out in the criteria paper of Bladé J, Samson D, Reece D, et al 1998 * Treatment with any investigational drug within 30 days prior to the addition to this protocol. * Subjects with severe cardiovascular disease. * Subjects with a history of neuropsychiatric disorder that requires hospitalization. * Subjects with thyroid dysfunction or uncontrolled diabetes mellitus (refractory to treatment). * Subjects with active infection and / or uncontrolled. * Pregnant or lactating women or women of childbearing age not practicing effective contraception. * Patients with previous psychiatric disease, especially moderate or severe depression or a history of severe psychiatric disorder, including psychosis, suicidal thoughts or suicide attempts. In severe depression cover the following points: (a) hospitalization for depression (b) electroconvulsive therapy for depression or (c) depression leading to the prolonged absence at work or to alter significantly the daily functions. Can be consider the entrance into the study of subjects with mild depression, where it is demonstrated by pre-treatment assessment individual's emotional state is clinically stable and in which case a treatment program formulated for the patient who will become part of the patient's medical record.