Treatment Patterns and Outcomes of Patients with Double-Class Refractory or Triple-Class Refractory Multiple Myeloma: A Retrospective US Electronic Health Record Database Study

Introduction: Patients with relapsed/refractory multiple myeloma (RRMM) resistant to multiple drug classes remain a high unmet need population, despite advances in MM patient care. The objective of this study was to assess real-world treatment patterns and outcomes in patients with RRMM who had failed multiple prior lines of therapy (LOT) and were refractory to multiple drug classes to identify gaps in their treatment pathways.

Methods: This longitudinal retrospective cohort study utilized the COTA de-identified real-world database derived from US electronic health records of partnered healthcare providers from Q3 1988 through Q1 2020. Adults with active RRMM previously exposed to a proteasome inhibitor (PI) and an immunomodulatory drug and who received ≥3 prior LOTs were identified. Patients were further categorized as refractory to a PI and an immunomodulatory drug (double-class refractory [DCR]) or additionally to an anti-CD38 monoclonal antibody (i.e. daratumumab; triple-class refractory [TCR]). Determining refractory status was based on International Myeloma Working Group criteria.

Index LOT was a new LOT after evidence of DCR or TCR status following ≥3 (DCR) or ≥4 (TCR) prior LOTs. Patient characteristics described included Eastern Cooperative Oncology Group (ECOG) performance status, International Staging System (ISS) stage, cytogenetic risk, age, index date, sex, and follow up time. Treatment pattern assessments included treatments received before/during/after index LOT, reasons for discontinuation, refractory status, and retreatment characteristics. Patient outcomes (overall survival [OS], duration of treatment [DOT], and time to next therapy [TTNT]) were analyzed using Kaplan-Meier survival analysis methods.

Results: After excluding patients who were aged <18 years at start of index LOT with no evidence of clinical activity and who participated in a clinical trial during index LOT, 381 (DCR) and 173 (TCR) patients were available for analysis. Median follow-up from index LOT initiation through end of data availability/death was 14 (DCR) and 8 (TCR) months. Demographic characteristics were consistent between DCR and TCR patients. Approximately half were aged ≥65 years (49% DCR; 53% TCR), majority had high-risk cytogenetics (56% DCR; 66% TCR) or prior autologous stem cell transplantation (>62%), and 14-16% had ISS stage III. Patients had a median of 3 (DCR) and 6 (TCR) prior LOTs.

Prior to index LOT, bortezomib and lenalidomide were the most commonly received PI and immunomodulatory drug (received by >98% of DCR or TCR patients) and the most common PI and immunomodulatory drugs to which patients were refractory (71% and 84% DCR; 76% and 83% TCR, respectively).

At index LOT, PI/immunomodulatory drug-based and daratumumab-based therapies remained the most common therapies. Bortezomib and lenalidomide had the longest time to refractory status and highest retreatment rates among DCR or TCR patients. Approximately 40% of TCR patients were retreated with daratumumab-based therapies after becoming refractory (Table).

After index LOT, 70% of DCR and 58% of TCR patients continued to a subsequent LOT. Patients most frequently discontinued index LOT due to disease progression (59% DCR; 60% TCR), toxicity (23% DCR; 25% TCR), or doctor preference (14% DCR; 10% TCR). Median duration of gaps between LOTs generally were shorter than 1 month (Table).

Median OS was 22.3 (DCR) and 11.6 (TCR) months. Median DOT was 3.3 (DCR) and 2.8 (TCR) months, and median TTNT was 4.1 (DCR) and 3.2 (TCR) months. In multivariate statistical analyses, inferior baseline ECOG performance scores, and high-risk cytogenetic abnormalities were associated with worse prognosis (higher risk of death, shorter DOT, and shorter TTNT) in DCR and TCR patients. Age was not a significant factor after adjusting for other baseline factors.

Conclusions: Treatment options are limited for US patients with DCR and TCR RRMM. DCR and TCR patients were frequently retreated with a PI, an immunomodulatory drug, or daratumumab, despite refractoriness to these agents. Many DCR and TCR MM patients stopped active MM treatment after discontinuing index treatment. Patients with DCR and TCR MM have poor prognosis, especially among high cytogenetic risk and poor performance status patients. This study provides the benchmark for new therapies, like BCMA-targeted agents, to be tested in this population.

Funding: GSK (Study 217353).

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