Factors associated with dose adjustment for the bortezomib, lenalidomide, dexamethasone regimen among patients with newly diagnosed multiple myeloma.

8039 Background: VRd (bortezomib/lenalidomide/dexamethasone) has become one of the established treatment regimens in the US for multiple myeloma (MM). Due to toxicities, dose adjustments are often required for VRd. This real-world study described the patient characteristics and factors associated with dose adjustment among MM patients treated with VRd as first line (1L) therapy. Methods: Adult MM patients treated with 1L VRd were selected from the Optum Clinformatics database (Nov 1, 2015-Sep 30, 2020). Patient characteristics were evaluated during a 6-month baseline period. Dose adjustments were defined based on lenalidomide (len) dose received during 1L. Receipt of > 15mg len was categorized as VRd regular, ≤15mg len as VRd lite, and initial len dose > 15mg reduced to ≤15 mg over treatment period as VRd reduced. Baseline factors associated with different VRd dose categories were studied using multinomial logistic regression. Results: Among the 1497 patients identified, the mean (SD) age was 69 (9.5) years (52% ≥70), 51% were male, 59% were White, 37% were frail, and 67% with Medicare. Baseline Charlson Comorbidity Index was 4.2, with hypertension (70%), hyperlipidemia (56%), renal impairment (26%), and CVD (25%) being the most prevalent comorbidities. Over half of the patients received an adjusted dose, VRd lite (33%) and VRd reduced (22%). Overall, for patients treated with 1L VRd, median follow-up was 16.2 months; median duration of 1L was 4.9 months (among those with confirmed end of therapy); and median TTNT was 14.5 months. Compared to VRd regular, use of VRd lite was over 6 times more likely to be associated with patients ≥75 years of age, about 2 times more likely to be associated with females, and about 40% less likely to be associated with commercial insurance vs. Medicare; VRd reduced was 1.3 times more likely to be associated with females, and 1.5 times more likely to be associated with frail patients (table). No differences were observed among different races. Conclusions: Over half of the MM patients treated with 1L VRd in the real-world were > 70 years of age and over one-third were frail. A large proportion of patients received a modified dose of VRd. Receipt of VRd lite dose was highly associated with older age (≥75 years), and receipt of VRd reduced dose was associated with frailty. These dose adjustments may potentially result in reduced efficacy of the VRd regimen in the real-world relative to controlled clinical trials, which needs to be assessed in future studies. [Table: see text]