Intestinal Microbiota Composition Is Associated with Minimal Residual Disease Negativity in Patients with Multiple Myeloma

Background:

Multiple myeloma (MM) patients who achieve minimal residual disease (MRD) negative status after upfront treatment have prolonged progression-free and overall survival compared with those who remain MRD(+) (Landgren CO, Devlin SM et al. Bone Marrow Transplant. 2016;51(12):1565-8). Commensal intestinal microbial composition has been associated with treatment outcomes in cancer patients. We sought to evaluate whether the composition of the intestinal microbiota is associated with MRD status in patients with MM.

Methods:

Stool samples were collected prospectively from 34 patients after completion of upfront therapy for MM at the time of MRD testing. MRD was assessed with next-generation flow cytometry of bone marrow aspirates (sensitivity 10^-5). Microbial analysis was performed via sequencing of 16S rRNA V4-V5 regions using the Illumina MiSeq platform and sequence data was analyzed using UPARSE (Edgar RC, Nature Methods 2013;10(10):996-8). The linear discriminant effect size method (LEfSe) (Segata N et al. Genome Biol. 2011;12(6):R60.) was used to compare detected clades among all groups and evaluate for associations with outcomes, using MRD as class and autologous stem cell transplant (ASCT) as subclass. Alpha diversity was calculated by the Inverse Simpson index and differential relative abundance were calculated using the phyloseq package and compared using the Wilcoxon rank sum test on the R statistical computing platform.

Results:

Among 34 patients evaluable for microbiota composition and MRD status, the median age was 62.5 years and 16 (47.1%) were MRD(-) at time of stool collection. 24 (70.6%) were treated with carfilzomib, lenalidomide, and dexamethasone as induction therapy (MRD(-): 14 (87.5%), MRD(+):10 (55.5%). 4 (28.5%) MRD(-) patients had autologous stem cell transplant(ASCT), compared with 10 (55.5%) who were MRD(+). In the cohort's samples, we observed 19 phyla, 315 genera, 654 species, and 1549 operational taxonomic units (OTUs). There was no significant difference in alpha diversity between MRD(-) (median 12.24, IQR = 8.76-13.98) and MRD(+) patients (median 12.44, IQR = 8.36 -16.23), p=0.6 by Wilcoxon rank sum test. A positive association with MRD negativity was noted with two butyrate-producing organisms, Eubacterium hallii (p=0.001) and Faecalibacterium prausnitzii (p= 0.006). To further evaluate these relationships, we performed a differential abundance analysis of these selected taxa in MRD(+) and MRD(-) patients at the genus and species level. The relative abundance of the genera Eubacterium and Faecalibacterium were higher in fecal samples from MRD(-) patients than MRD(+) patients (Eubacterium MRD(-): median 4.51% (IQR = 2.83 - 7.32%) vs. MRD(+): median 3.07% (IQR = 1.35 - 3.87%), p=0.0326; Faecalibacterium MRD(-): median 1.68% (IQR = 0.69 - 7.48%) vs. MRD(+): median 0.003% (IQR = 0 - 3.19%), p=0.022. The relative abundance of both species of interest were higher in MRD(-) patients than in MRD(+) patients: E. hallii MRD(-): median 2.67% (IQR = 2.11 - 3.98%) vs. MRD(+): median 1.01% (IQR = 0 - 2.16%), p=0.001; F. prausnitzii MRD(-): median 1.43% (IQR = 0.53 - 7.28%) vs. MRD(+): median 0.3%, (IQR = 0 - 2.54%), p=0.022. Other species of Eubacterium and Faecalibacterium were not significantly differentially abundant between the two groups.

Conclusions:

Intestinal microbiota containing several butyrate-producing anaerobes appear to be associated with MRD-negativity in patients with myeloma, with higher relative abundance of Eubacterium hallii and Faecalibacterium prausnitzii in MRD(-) patients compared with MRD(+) patients. Butyrate and other short-chain fatty acids are biologically active metabolites formed during microbial fermentation of dietary or host-derived carbohydrates, which supply the host with energy and also modulate immunity, including exerting anti-inflammatory functions. Microbes of the genus Eubacterium have been associated with reduced risk of relapse in several hematologic cancers after allogeneic hematopoietic cell transplantation, including MM (Peled JU, Devlin SM et al. J Clin Oncol 2017;35(15):1650-9). This is first study to our knowledge to suggest an association between gut microbiota and MRD status in patients with myeloma and supports further investigation of a potential role for intestinal microbiota in the natural history and treatment of myeloma.