Abstract
Background: Proteasome inhibitors (PIs) represent one of the most effective classes of therapy for patients with multiple myeloma (MM) and are incorporated in many of the current treatment regimens. The first-generation PI, bortezomib, has shown impressive results in patients with either newly diagnosed or relapsed/refractory MM, but once patients become resistant, treatment is increasingly challenging. Although the existing data show that the second-generation PI, carfilzomib, is highly efficient, there is still limited knowledge regarding the response to carfilzomib-based therapy in bortezomib-resistant patients. The aim of this study was to evaluate carfilzomib treatment performance in bortezomib-sensitive versus -refractory patients, in a real-life eastern European country setting. Methods: We retrospectively evaluated 127 adult patients exposed to bortezomib with relapsed or refractory MM, that subsequently received a carfilzomib-based therapy. We investigated the differences in the overall response rate (ORR), progression-free survival (PFS), and overall survival (OS) after carfilzomib-based therapy between the two patient groups. Results: The ORR in the bortezomib-sensitive group was significantly higher than that in the refractory group, leading to a superior PFS in this category of patients. For patients presenting with a high cytogenetic risk, we observed a significant difference in PFS between the bortezomib-sensitive and -refractory group, while standard cytogenetic risk patients presented a similar PFS regardless of the bortezomib sensitivity status. In addition, in patients with ISS (International Staging System) stage I or II, the previous sensitivity to bortezomib correlated with an improved PFS, while for patients with ISS stage III, both groups had a comparable PFS. No significant differences in OS were observed between the two groups. Conclusions: In countries where novel or experimental therapies are not readily available, carfilzomib-based therapy can still be a viable therapy option for patients presenting with bortezomib-refractory status, an ISS stage III, and standard cytogenetic risk.