Appropriate Dose Adjustment of Dexamethasone Does Not Compromise Outcomes in Relapsed Refractory Multiple Myeloma

Abstract Background: Dexamethasone (dex) is an integral part of various anti-myeloma regimens both in the frontline and relapsed/refractory (RR) setting. Several clinical trials have shown that dex adds to the efficacy of novel therapeutic agents for multiple myeloma (MM). Yet, a substantial number of patients are intolerant to even the standard of care low-dose dex (40 mg weekly), especially in heavily pre-treated RRMM, possibly due to cumulative steroid toxicities and thus, require dex dose adjustments. There is a concern of compromising the efficacy of anti-MM regimens by adjusting the dex dose lower. We describe the frequency of dex dose adjustment, characteristics of patients who required it and its effect on patient outcomes in a large prospective clinical trial of pomalidomide (pom) and dex in RRMM (MC0789). Methods: We utilized data from the Pom-dex trial (MC0789), which treated RRMM patients in different cohorts of pom (2 vs. 4 mg; 21 vs 28 days cycle) with fixed dose dex (40 mg orally weekly). Patients were divided into 2 subgroups, with any dose adjustment/elimination of dex vs. not. Continuous and categorical variables were compared between the two groups using two-sample t-test/Wilcoxon rank sum test or Chi-squared test, respectively. Logistic regression and Cox regression models were used to find the univariate and stepwise multivariate predictors of response to treatment and overall mortality, respectively. Kaplan-Meier method was used to estimate overall survival (OS) at 1, 3, and 5 years. All statistical tests were two-sided with the alpha level set at 0.05 for statistical significance. Results: Results from the MC0789 clinical trial have been reported previously. Almost half of all treated patients in this trial had dex dose adjusted (n=175/343; 51%). The median number of cycles for the first dose adjustment in this group was 3 (range 1-62), with 46.5% of patients (n=82) having multiple dose adjustments and majority (58.3%, n=102) within the first 3 cycles of treatment. Patients in the dose adjustment group were significantly older (mean 65 vs 60 years; p=0.0001). Males, Whites and patients diagnosed before 2006 or with normal cytogenetics also had a higher incidence of dex dose adjustment, though this was not statistically significant. Patients with dex dose adjustment had a longer duration of treatment (mean 339 days) as compared to the non-adjusted cohort (mean 123.65 days) (95% CI 160.13, 270.58; p Conclusion: Our analysis established that in these heavily pre-treated RRMM patients, appropriate dose adjustment of dex did not compromise their response rates; patients remained on treatment significantly longer and had an improved survival. Majority of patients (58.3%) requiring dex dose adjustment had it instituted early during treatment ( Download : Download high-res image (70KB) Download : Download full-size image Disclosures Kumar: Skyline, Noxxon: Honoraria; Celgene, Millennium, Onyx, Janssen, Noxxon, Sanofi, BMS, Skyline: Consultancy; Celgene, Millennium, Onyx, Novartis, Janssen, Sanofi: Research Funding.