- Summary Carfilzomib has been established in previous years as a treatment for patients with relapsed and/or refractory multiple myeloma (RR-MM). A retrospective multicentre study to evaluate the clinical use of carfilzomib for RR-MM outside of a clinical trial setting was conducted by our group. One hundred and thirty-five patients were included. All patients had been previously exposed to bortezomib and 93% had also been treated with lenalidomide. The vast majority of patients received carfilzomib as part of a two- or three-drug combination. The overall response rate was 47·2%. Multivariate analysis revealed bortezomib resistance, lenalidomide resistance and albumin <35 g/l to negatively impact the likelihood of achieving response. The median duration of response was 8·4 months, and was significantly higher in patients receiving three-drug combination and patients presenting without extramedullary disease. The median progression-free survival and overall survival for the entire cohort was 4·9 months (95% confidence interval [CI] 3·8–6·4) and 12·2 months (95% CI 9-not reached), respectively. Toxicity was manageable, although treatment-related death was seen in 5% of patients. In the setting of progressive multiple myeloma, carfilzomib in a combination regimens yields effective results with a manageable toxicity.