[Retrospective study comparing low-dose versus standard dose of bortezomib in patients with multiple myeloma]

Bortezomib is a selective inhibitor of the proteosoma that is used in multiple myeloma. In combination with other antineoplastic drugs, it has a well-documented impact in progression-free survival rates and overall survival rates with standard doses (1.3-1.5 mg/m(2)). However, up to 88% of patients on standard doses have unwanted side effects (neutropenia, neuropathy or anemia. Standard dose (1.3 mg/m(2)) is used in almost all patients and low dose (0.7-0.8 mg/m(2)) is reserved for patients with kidney disease and neuropathy.

We aim to describe clinical, cytological, and cytometric outcomes, as well as overall survival and side effects of low dose versus standard dose of bortezomib in our institution.

Retrospective, descriptive study based on data recovered from clinical charts of 48 multiple myeloma patients treated in our hospital between 2011 and 2013. We included data on age, gender, type of multiple myeloma, serum albumin, serum creatinine, beta 2 microglobulin, calcemia, imaging studies, disease stage, pre-and post-therapy bone marrow studies, adverse events and rate of progression. We also recorded events like date of death or of the last medical appointment.

Forty-eight multiple myeloma patients were treated with bortezomib-cyclophosphamide-dexamethasone. Twenty-one patients received low dose and 27 patients were treated with the standard dose. No statistical differences between the two groups were found for clinical response (p=0.6), cytological response (p=0.28), flow cytometric response (p= 0.3), rate of adverse effects and overall survival rates.

This retrospective analysis suggests that lower doses of bortezomib have similar effects in disease control measured by flow cytometry and cytology compared to standard doses in multiple myeloma patients.