Clonal Hematopoiesis: Exploiting Molecular Landscape of Multiple Myeloma Patients for Choosing the Most Appropriate Therapeutic Strategy

Background. Recent studies have identified in the blood of ageing people, the presence of somatic mutations in hematopoietic cells, a condition referred as clonal hematopoiesis of unknown significance (CHIP). CHIP is associated with a 0.5-1% risk of progression to a non-plasma-cell hematologic neoplasm, in particular myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). In cancers, the prevalence of CHIP is higher compared to healthy population, especially for those who have been exposed to cytotoxic chemotherapy or radiation. The presence of CHIP clones has been documented also in Multiple Myeloma (MM) with a poorer outcome in patients receiving ASCT. Moreover, clonal hematopoiesis represents an age-related risk factor for cardiovascular disease-related morbidity and mortality as well. Here we have evaluated the presence of CHIP at time of diagnosis and after 12-24 months of treatment, by focusing on its relationship with prognosis and therapy-related cardiovascular events (CVs), to comprehensively evaluate risk-assessment of MM patients. A special analysis on tumor and non-tumor cells has been also done.

Methods. High-depth targeted sequencing of peripheral blood (PB) from 65 NDMM patients was analyzed by NGS sequencing using a panel of 36 CHIP-related genes. Discovered variants with a VAF >40%, frequency in general population >1% and with neutral/uncertain impact on protein function were filtered out. The selected somatic mutations and their VAFs were correlated with demographic and clinical parameters, including age, sex, R-ISS stage, outcomes, and occurrence of adverse events with a focus on cardiovascular events (CVs). Subsequent analyses at 12-24 months after therapy were also run and for those patients with available bone marrow (BM) samples, the non-tumoral fraction (CD138^neg cells) was analyzed too.

Results. Somatic mutations were detected in ~45% of our cohort with a VAF between ~1% and 34%. The most frequently mutated gene was TET2 followed by DNMT3A. Higher β2-microglobulin and lower hemoglobin levels were observed in CHIP carriers; high-risk (R-ISS 3) patients showed greater occurrence of CHIP and higher VAFs respect to lower disease stage (R-ISS1), regardless of age. Indeed, no correlation between CHIP and age was observed. Analyses on CD138^neg cells from BM samples, confirmed data observed on PB, with high correlation (Pearson R=0.97, p<0.0001) of CHIP between two sources. A slightly increment of VAFs mutation (p=0.058) was observed during follow -up, mainly in DNMT3A, TET2, ASXL1 and TP53 (p=0.0123) genes whilst a stable frequency affected all other genes, thus suggesting coexistence of small clones with different clonal evolution. Regarding CVs, higher prevalence of CHIP was observed in patients with high blood pressure and in those with prior atherosclerotic cardiovascular conditions. Preliminary data on progression-free and event-free survivals hint at worse outcome for CHIP carriers, but longer follow-up is needed to fully support these data.

Conclusions. Micro-clones in the hematopoietic compartments of MM patients were found to slightly increase in size and remain quite stable in terms of type of mutated genes during disease evolution thus suggesting that biological landscape is not affected by a specific therapy. On the other side, the presence of this clones, as indicated by our data, correlates with a more aggressive disease and, worse outcome. Based on our data we speculate that BM limited-growing clones, facilitates a pro-inflammatory environment, as already reported for DNMT3A and TET2 in PB. Such a scenario may account for tumor growth support of BM microenvironment and for the increased toxicity, mainly CVs, in response to therapy. Overall, we propose a specific management of CHIP-carrying MM patients, especially for what concern therapy-related toxicity.

Conticello:Janssen: Honoraria; Takeda: Honoraria; Amgen: Honoraria; GlaxoSmithKline: Honoraria; Bristol Myers Squibb: Honoraria; Sanofi: Honoraria. Lemoli:AbbVie: Consultancy; Stemline Therapeutics: Consultancy; Janssen: Consultancy; Jazz: Consultancy; Daiichi Sankyo: Consultancy; Servier: Consultancy; Novartis: Consultancy; Celgene: Research Funding.