P-351: SINGLE VS TANDEM TRANSPLANT IN HIGH-RISK MULTIPLE MYELOMA PATIENTS: A REAL-LIFE SINGLE-CENTRE ANALYSIS

Introduction: Autologous stem cell transplant (ASCT) remains the recommended treatment in eligible Multiple Myeloma (MM) patients. Some studies (EMN02, STAMINA) have proven an advantage in terms of PFS and OS in high-risk (HR) MM that received tandem (T) ASCT, leading it to be the standard of care in many European countries, despite data being based on post-hoc analyses including a very small number of patients. Furthermore, no modern study has been designed with T ASCT and the validity of these results are yet to be confirmed with newer drug combinations.

Methods: We retrospectively analyzed data from newly diagnosed MM patients who underwent ASCT in a single tertiary care center in order to evaluate outcomes of single (S) vs tandem (T) ASCT in HR patients according to cytogenetics [t(4;14, t(14;16), del17p, chromosome 1q and 1p abnormalities] and R2-ISS stage 3-4. PFS and OS were analysed by Kaplan-Meier methods and compared by log-rank test. Factors affecting PFS were searched by Cox regression analysis.

Results: a total of 157 patients were included in the study, 105 who received S (67%) and 52 (33%) T ASCT. The two groups of patients were similar regarding age (60 years in both populations), ISS stage 3 (23% in the S subgroup vs 17% in the T), HR cytogenetics (31.5% vs 27%), R-ISS stage IR-HR (67% vs 65.4%), R2-ISS 3-4 (39% vs 33%), renal failure (13.3% vs 17.3%), as well as the proportion of patients receiving 3 drugs induction treatment (66.3% vs 67.5%), undergoing consolidation (33.3% vs 23%) and receiving maintenance post ASCT (49.5% vs 42.3%). Post-transplantation, CR or better was achieved by 53.3% and 50% of S and T ASCT (p=0.411), respectively. After a median follow-up of 84 months (range 36-160), PFS of patients receiving S or T ASCT were not significantly different neither according to cytogenetic HR (31.3 vs 36.5 months; p=0.292), nor by R2-ISS stage 3-4 (44.7 vs 42.7 months; p=0.691). Overall survival was also similar between HR patients according to cytogenetics or R2-ISS 3-4 receiving either S or T ASCT (78.4 vs 65.5 months, p=0.855; 82.3 vs 85.1 months; p=0.983, respectively). Univariate Cox regression analysis selected HR cytogenetics, R2-ISS 3-4, no consolidation, no maintenance and response < CR as factors negatively affecting PFS while number of ASCT was not statistically significant. HR cytogenetics (HR=2.9; CI 95%: 1.5-5.8; p< 0.001), no maintenance (HR=1.8; CI 95%: 1.2-2.8; p=0.008) and suboptimal response (HR=2.1; CI 95%: 1.4-3.2; p=0.001) remained significant in multivariate analysis.

Conclusions: our study showed that, in the era before anti-CD38 antibodies, single transplant seems to have had the same effectiveness as tandem transplant in terms of both PFS and OS in HR MM patients defined by cytogenetics or by R2-ISS stage.