VELCADE as Maintenance Treatment in Patients With Multiple Myeloma Following Autologous Peripheral Blood Stem Cell Transplantation (PBSCT)

Inclusion Criteria:

* Patient having received tandem transplants with high-dose melphalan and autologous PBSCT within 3-6 months prior to inclusion into this protocol
* Patients with measurable minimal residual disease (very good partial remission \[VGPR\]) or patients in partial remission (PR) or patients with stable disease (SD) at the time of inclusion in the study
* Patient must agree to participate in the study.
* Patient agrees to use an appropriate method of contraception.
* Willingness and ability to comply with the study protocol for the duration of the study

Exclusion Criteria:

* Patient showing signs of disease progression
* Patient has a platelet count \< 100 x 10\^9/L within 14 days before enrollment.
* Patient has an absolute neutrophil count \< 1.0 x 10\^9/L within 14 days before enrollment.
* Patient has a calculated or measured creatinine clearance \< 30 mL/minute within 14 days before enrollment.
* Patient has \>= Grade 2 peripheral neuropathy within 14 days before enrollment.
* Patient has hypersensitivity to bortezomib, boron, or mannitol.
* Patient has received prior treatment with bortezomib
* Patient is pregnant or nursing
* Patient has received other investigational drugs within 14 days before enrollment
* Patient has progressive disease
* Patient has a Karnofsky performance status \< 60%
* Patient has a life expectancy of \< 3 months
* Patient has received disease modifying agents following autologous stem cell transplantation other than aminobisphosphonates such as interferon-alpha or glucocorticosteroids
* Patient currently enrolled in another clinical research study and/or receiving an investigational reagent for any reason.