Improved survival in multiple Myeloma patients undergoing autologous stem cell transplantation is entirely in the standard cytogenetic risk groups.

INTRODUCTION: Novel drugs and drug combinations have improved outcomes for multiple myeloma patients. However, subgroups of patients still have a poor progression-free survival (PFS) and overall survival (OS). In an attempt to identify how the novel drugs affect the outcome in standard-risk and high-risk patients, respectively, we have investigated 715 multiple myeloma (MM) patients who have undergone high dose treatment followed by autologous stem cell transplantation at our center during 1995 - 2020. Outcomes during three time periods, 1995-1999 (period I), 2000-2009 (period II), and 2010-2020 (period III), were compared separately for standard-risk and high-risk patients. Risk stratification was based on chromosome analysis for periods II and III. RESULTS: The whole cohort of patients showed significantly improved OS with time during the three periods being at a median of 5.8, 7.0, and 10.0 years, respectively. There is also a weak tendency for improved PFS, that is, a median of 2.4, 2.6, and 2.9 years, respectively, during the same periods. However, the separate analysis of standard-risk and high-risk patients showed that the overall improvement with time was due to improved standard-risk patients (median OS 8.4 years for the period I and not reached for period II and III). In contrast, no significant improvement was seen in high-risk patients. For patients with del17p, PFS was even worse during period III as compared to period II (median 1.6 vs 3.2 years respectively). CONCLUSION: Our results show that the dramatic improvement in outcome for MM patients during the last 20 years only applies for standard-risk patients, while high-risk MM patients still are doing poorly, indicating that the novel drugs developed during this time are preferentially effective in standard-risk patients. New treatment modalities like CAR-T cells, CAR-NK cells, and/or bispecific antibodies should be tried in clinical studies early in the course of the disease, especially in patients with high-risk cytogenetics.