Long Term Significance of Response in Multiple Myeloma After Stem Cell Transplantation.
Authors: Martínez-López Joaquin , Blade Joan , Gomez del Castillo M. Carmen , Mateos Maria Victoria , Alegre Adrian , Garcia-Laraña José , Sureda Anna , de la Rubia Javier , Conde Eulogio , Martínez Rafael , de Arriba Felipe , Zamudio Jose Luis Gomez , Besalduch Juan , Cabrera Rafael , Biguria M. Cruz , Moraleda Jose Maria , Miguel J.F San , Lahuerta Juan José 
Published: October 2019

Abstract
Abstract 1811
Poster Board I-837
The prognostic significance of achieving complete remission (CR) in Multiple Myeloma (MM) has finally been accepted. However, available studies have been based on series with a median follow-up around 5 years. This time period is insufficient according to the current life expectation of MM.

Aim
To establish the real effect of prognosis of the different response categories in a cohort of MM patients treated with autologous stem cell transplantation (ASCT) after long term follow up.

Patients and methods
Follow-up from diagnosis of 344 MM patients transplanted between 1989 and 1998 has been updated. These patients were previously included in a study aimed at establishing the post-ASCT response significance in MM and to validate the EBMT classification (Br J Haemat 2000;109:438-46). It was possible to update the follow up of 322 patients as at April 2009. At this date 99 patients were alive with a median follow-up form diagnosis of 12.5 years. Response categories and evaluated cases were: i) Complete Response (IF-) (CR), n= 84 ii) near Complete Response (EF-/IF+) (nCR), n= 66 iii) Very good partial response (VGPR) (<90% reduction of M component), n= 66 iv) Partial response PR (reduction of M component between 90-50%), n= 113 v) Stable Disease (SD), n= 12, y vi) Progression (PD), n=14 Survival analyses were performed by Kaplan-Meier curves (log-rank test). Cox logistic regression was employed to establish variables associated with a higher survival.

Results
Significant differences in overall survival (OS) and event free survival (EFS) were found between CR and nCR groups (p 0.01 and 0.0022, respectively); or between CR and VGPR (p 0.0001 and 0.0035); no differences were detected between nRC and VGPR groups (p 0.21 and 0.99) and between these groups and PR group (p 0.1 y p 0.8). OS and EFS of patients with ED o PD were lower than the rest of the groups. Overall survival at 12 years was 43% in CR patients, 21% in nCR, 20% in VGPR, 30% in PR, 8% in SD and 0% in PD groups. Median survival (OS, EFS respectively) of each group was 91 months and 36 m, 26 m and 21 m, 20 m and 15 m, 31 m and 12 m, 8 m and 5 m, and 6 and 1 month.
Land-mark study (10 years) found a plateau phase in OS and EFS after 11 years. Twenty two percent of patients are still alive with stable status between 11 and 15.54 years and only two cases had relapsed in the non CR group. In a regression study for OS, response was only one variable with statistical significance (CR P <0.0000, OR 0.044, IC-95%: 0.020-0.30).

Conclusions
In MM achieving CR after ASCT is the most important prognostic factor even after long-term follow-up. Relapse rate is very low in patients with >11 years of follow-up, this could mean a cure for patients in CR.

Disclosures
No relevant conflicts of interest to declare.