Importance of Complete Remission on Predicting Overall Survival in Patients with Lower-Risk Myelodysplastic Syndromes (MDS)

Background

Lower-risk (LR) MDS (Low/Int-1 per International Prognostic Scoring System (IPSS)) are a heterogeneous group of disorders characterized mainly by refractory anemia and transfusion dependency. As survival of this patient (pt) population is measured in years. Goals of therapy focus on decreasing blood transfusions, improving quality of life, while minimizing treatment toxicities. While achieving complete remission (CR) in higher-risk MDS correlates with improved overall survival (OS), its relationship to OS in LR MDS is not well defined. We evaluated the impact of achieving CR on OS in LR MDS and defined the clinical characteristics that may predict for this response in this pt population.

Method

Included pts were diagnosed with MDS (per 2008 WHO criteria) and had LR disease with clinical and pathologic data collected from MDS Clinical Research Consortium institutions. Only pts with bone marrow blasts of 5-9% who would thus qualify both as having LR MDS and for being eligible to assess CR were included. Responses (including CR, PR, HI, stable disease and progressive disease) were defined per International Working Group 2006 criteria. OS was calculated from the time of achievement of best response to time of death or last follow-up. Cox proportional hazard analysis that included all clinical variables and treatment characteristics was used to identify independent prognostic factors.

Results

Of 1470 pts included in the database, 999 identified with LR disease, and 174 had bone marrow blasts of 5-9%. The median age was 60 years (range, 22-87), and 37% were female. Median neutrophil count was 1.25 X 10⁹\L (range, .10-51.0), hemoglobin was 9.8 g/dl, platelets were 109 k/ml (range, 18-562), and bone marrow blasts were 6% (range, 5-9%). Best responses to therapy included: 26 pts (15%) with CR, 10 pts (6%) with PR, and 13 pts (7%) with HI. Among pts who achieved CR/PR/HI, 27 received HMA (25 with azacidtine +/- combination and 2 with single agent decitabine), 16 intensive chemotherapy, 2 lenalidomide, and 4 received other therapies. With a median follow up from diagnosis of 31.2 months, the median time from diagnosis to best response was 11.9 months (range, .69-81.0) and was similar in pts who achieved CR compared to PR/HI (11.5 vs. 12.4 months, respectively, p = .74). The median OS from time of CR/PR/HI for the entire cohort was 21.3 months. The median OS for pts who achieved a CR was longer compared to pts with PR/HI (46.5 vs. 18.5 months, respectively, p = .03). In multivariate analyses that included clinical variables and treatment history, achieving CR remained an independent prognostic factor for longer OS (HR .32, p = .03) but no individual demographic, clinical or treatment variables were predictive of CR.

Conclusions

Similar to pts with higher-risk MDS, LR MDS pts who achieve CR to therapy have improved OS compared to those with PR or HI. CR is thus an important endpoint in LR MDS, though is difficult to predict. As OS is measured in years in LR MDS, CR may be used as a surrogate endpoint for OS in clinical trials in this pt population.