Bortezomib as First Salvage Therapy for Myeloma Patients Previously Exposed to Bortezomib as Initial Treatment.

Inclusion Criteria: Patients satisfying all of the following criteria will be enclosed in the study: * Age ≥ 18 years old * Patients with documented multiple myeloma that received bortezomib-based regimens as first line treatment (both in clinical practice or clinical trials) even if followed by ASCT (Autologous stem cell transplantation) and that after their first line treatment's clinical or biochemical relapse received again a bortezomib-based treatment according to current clinical practice and/or Italian Societies of Hematology (SIE), Experimental Hematology (SIES) and Transplantation (GITMO), International Myeloma Working group (IMWG) and/or National Cancer Comprehensive Cancer Network (NCCN) guidelines/treatment recommendations. * Signed Informed Consent form if feasible Exclusion Criteria: * Patients not treated with bortezomib as first line therapy and/or second line therapy * Patients with more than one relapse before bortezomib re-use * Patients unable to understand and sign Informed Consent form (see exceptions listed in section 8 "Informed consent") * Patients who received bortezomib at relapse in combination with any investigational drug not-approved.