The phase I/II study of melphalan-prednisolone-bortezomib (MPB) therapy in Japanese patients with previously untreated multiple myeloma (MM) who are ineligible for hematopoietic stem cell transplantation (JPN-102 trial) (registered between July 2008 and March 2011) showed an overall response rate in the MPB arm equivalent to that of the VISTA trial. In this study, we followed up the clinical data of 92 of the 101 patients registered in the JPN-102 trial to clarify the long-term outcomes of MPB therapy. The median follow-up period was 50.8 (0.9-66.1) months. The median age of this cohort was 72 (48-84) years. The median progression-free survival was 25.7 (95%CI: 21.3-33.9) months and the overall survival rates at 1, 3 and 5 years were 98, 86 and 76%, respectively. There was no significant difference in either progression-free survival or overall survival when comparing a total bortezomib amount of 39 mg/m2 or more being administered versus less than 39 mg/m2. The outcomes of the JPN-102 cohort appeared, at a minimum, to not be inferior to those of the MPB cohort in the VISTA trial. A prospective trial is needed to establish the MPB regimen as being suitable for Japanese patients with multiple myeloma.