P-223: Pomalidomide (P) in Relapsed/Refractory Multiple Myeloma (RRMM): Analysis of Real-World Data from an Ongoing, National, Multi-Center, Non-Interventional Study

Introduction: Treatment options in patients with RRMM refractory to bortezomib (V) and lenalidomide (R) are limited. Potential approved treatment options include pomalidomide/dexamethasone (Pd) after at least two prior lines of therapy (LoT) (including both V and R) and PVd after at least one prior LoT (including R). The aim of this ongoing, multi-center, non-interventional study is to prospectively collect real world data in patients with RRMM treated with Pd or PVd in Austrian clinical routine practice.

Methods: Safety (adverse events [AEs]) and efficacy data (objective response rate [ORR]; ≥partial response] were collected from adult patients with RRMM treated with Pd or PVd until progression or unacceptable toxicity; progression-free survival [PFS]) was calculated. Descriptive statistics were used; the study was not powered for direct comparison of cohorts.

Results: From 09/2014 to 12/2022, 127 patients were enrolled by 9 Austrian centers (126 eligible patients). At inclusion, the median age was 70 years (range 38-90); 33 patients (26%) were >75 years; 65 patients (51%) were male. The median number of prior lines of therapy was 3 (range 1-8). Prior treatments included an immunomodulatory drug (87%), a proteasome inhibitor (92%), an anti-CD38 antibody (18%) and autologous stem cell transplantation (ASCT) (52%).
The median number of P treatment cycles was 10 (range 1-90). At cycle 10, 74% of patients still received P at a dose of 4 mg, while only 14% received dexamethasone (dex) at the dose of 40 mg.
Safety information was available for 99 patients (78.6%). Out of 651 AEs, 249 (38.2%) were drug related. Most AEs were non-serious (77%); 13.7% required hospitalization, 0.5% were life-threatening and 0.5% were fatal (both not drug related). The most common AEs were neutropenia (21%) and infections (18%). The most common reason for treatment discontinuation was tumor progression (n=73, 58%); death occurred in 6 patients (unrelated to treatment with P (5%); six patients (5%) discontinued treatment due to toxicity. At data cutoff, 16 patients (13%) were still on treatment.
The median PFS (months) was 16.4 for all [n=126], 12.8 for Pd [n=50], 22.7 for PVd [n=15] and 32.4 for Pd+additional active substance [Pd+x; n=61].The ORR and CR (both in %) were 64/20 for all [n=114], 49/13 for Pd [n=45], 69/38 for PVd [n=13] and 75/21 for Pd+x [n=56].

Conclusions: This interim analysis demonstrates that Pd is an effective and well tolerated treatment in patients with RRMM in clinical practice. Dose reductions of P were less frequent compared to dex (26% vs. 45.6% with dex), suggesting its good tolerability. Presented response data for Pd (PFS: 12.8 months; ORR: 49%) are longer compared to data from earlier, randomized trials (MM-003, NCT01311687). Considering the limitations of noninterventional studies, these results may reflect clinicians' increasing practical experience with Pd and PVd. As indicated by the increase of median PFS, efficacy of Pd may be enhanced by addition of a third antimyeloma agent.