Survival differences in multiple myeloma in Latin America and Asia: a comparison involving 3664 patients from regional registries

In previous observational studies, we have separately characterized patients with multiple myeloma (MM) both from Latin America (LA) and from Asia. Here, we analyze these two datasets jointly, in order to assess the overall survival (OS) in these two world regions. Data were available from 3664 patients (1968 from LA and 1696 from Asia); all of whom diagnosed between 1998 and 2007. Approximately, 26% of patients in both world regions underwent transplantation. OS (from diagnosis of MM) was explored with Kaplan-Meier analyses and Cox proportional hazards models. Patients from LA were significantly younger and had hypercalcemia more often than Asian patients, who in turn had higher proportions of anemia and International Staging System (ISS) stage III disease. The median OS was 56months in LA, and 47months in Asia (hazard ratio [HR]=0.83; 95% confidence interval [CI], 0.76 to 0.91; P<0.001). In multivariable analysis, age, ISS stage III, anemia, hypercalcemia, and world region remained significantly associated with OS (P<0.001 for all covariates). These results were largely driven by patients not undergoing transplantation, as no difference in OS emerged between the two world regions in univariable or multivariable analysis for transplanted patients. Despite adverse prognostic features differentially favoring each region, and adjusting for such differences, we found an OS advantage for patients from LA, in comparison with contemporaneous patients from Asia. Whether this is due to different biological features, differences in access to novel agents (especially thalidomide in earlier periods of the study), unmeasured confounders, or the play of chance, remain unknown.