Real World Assessment of Treatment Patterns and Outcomes Among Multiple Myeloma Patients across Different Risk Stratification Criteria in the United States: A Retrospective Cohort Study
Authors: Rahman Motiur , Kim Christopher , Mateus Jazmine , Keegan Alissa 
Published: November 2021

Abstract
Background: Despite the development of highly active novel agents, high risk (HR) multiple myeloma (MM) patients continue to demonstrate relatively poor prognosis. Limited data is published on how treatment patterns with risk stratification systems have changed over time. Moreover, real world studies using electronic health records (EHRs) have not evaluated the performance of risk stratification systems with real world outcomes. This study aims to evaluate the ability to implement three different risk stratification systems - international staging system (ISS), revised ISS (R-ISS), and high-risk chromosomal abnormalities (HRCA, defined as presence of del(17)p, t(4;14) and/or t(4;16)) [Palumbo et al. 2015] - to characterize treatment patterns and associated outcomes [real world overall survival (rwOS) and real world progression free survival (rwPFS)] among newly diagnosed MM (NDMM) patients in the US community practice.
Methods: This study used Flatiron Enhanced MM EHR de-identified database (New York, NY). Newly diagnosed MM patients (≥ 18 years) were diagnosed from January 2015 through June 2020 (cohort 1 - for studying treatment distribution) with follow-up through December 2020, and from January 2015 through December 2018 (cohort 2 - for rwOS and rwPFS), with follow-up through December 2020. Patients with malignancies other than MM were excluded. Proportion of rwOS was measured from treatment initiation until death, and median rwPFS was measured from treatment initiation until death, progression, or start of new line of therapy using Kaplan-Meier method.
Results: A total of 1,979 and 1,382 patients were eligible in cohorts 1 and 2, respectively. In both the cohorts, approximately 18% (cohort 1: N=367, cohort 2: N=248), 41% (cohort 1: N=805, cohort 2: N=566), and 37% (cohort 1: N=738, cohort 2: N=508) were HR patients according to the R-ISS, ISS, and HRCA criteria, respectively. Approximately half of the HR patients were ≥70 years old (52% for R-ISS III and ISS III, and 47% for HRCA), with chronic kidney disease stage ≥3 by eGFR for 54% R-ISS III and ISS III, and 34% high risk CA, and ECOG score ≥2 for 18% R-ISS III, 19% ISS III, and 14% HRCA patients.
Triplets were the most frequent treatment regimens (62% for R-ISS III and II, and 66% for R-ISS I; 59% for ISS III, and 65% for ISS II and I; 65% for HRCA and 61% for standard risk CA(SRCA) with proteasome inhibitors (PIs) / immunomodulatory agents (IMiDs) / dexamethasone being most common regimen across all the risk stratification criteria. Quadruplet agent use was higher in R-ISS III and ISS III categories (6.8% vs. 3.3% for R-ISS III vs. I; 6.3% vs. 2.8% for ISS III vs. I).
The median rwPFS in HR patients were shorter than the lower risk subgroups (R-ISS III: 8.8 months [95% CI 7.1 - 11.0], R-ISS II: 12.1 months [95% CI 10.7 - 13.6], R-ISS I: 23.5 months [95% CI 13.8 - .]; ISS III: 10.4 months [95% CI 8.5 - 11.5], ISS II: 12.7 months [95% CI 10.7 - 14.3], ISS I: 16 months [95% CI 12.2 - 19.5]; HRCA: 10.1 months [95% CI 8.8 - 12.1], SRCA: 13.1 months [95% CI 11.3 - 14.8]).
The 2-year rwOS was lower in the HR subgroups (R-ISS III: 0.65 [95% CI 0.59 - 0.70], R-ISS II: 0.79 [95% CI 0.76 - 0.81], R-ISS I: 0.91 [95% CI 0.85 - 0.95]; ISS III: 0.68 [95% CI 0.64 - 0.72], ISS II: 0.81 [95% CI 0.77 - 0.84], ISS I: 0.89 [95% CI 0.85 - 0.92]; HRCA: 0.75 [95% CI 0.71 - 0.79], SRCA: 0.79 [95% CI 0.76 - 0.81]).
Discussion: This study found that median rwPFS and 2-year rwOS proportions were consistently lower among HR patients compared to the standard risk individuals. The majority of the HR patients were older, with decreased levels of physical functioning and worse indicators of end-organ damage including renal function, anemia, and hypercalcemia. Most patients received triplets with frequent use of PIs likely for aggressive disease control among HR patients. Some HR patients received more quads than lower risk patients suggesting treatment intensification, but HR patients also received stem cell transplants at a lower rate. Although a smaller proportion of patients have all the data collected needed for R-ISS classification, the consistent findings across treatment outcomes suggest that R-ISS is implementable in real world studies and has a greater discriminatory ability than ISS or HRCA alone. Overall, this study suggests that HR patients have relatively poor outcomes which calls for the study of risk-adapted implementation of novel therapies among this patient population in the US community practice settings.
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Disclosures
Rahman: Amgen Inc.: Current Employment, Current holder of stock options in a privately-held company. Kim: Amgen: Current Employment, Current equity holder in publicly-traded company. Mateus: Amgen Inc.: Current Employment, Other: Work at Amgen as a contract employee through DOCS. Keegan: Amgen Inc.: Current Employment, Current holder of stock options in a privately-held company.