Abstract 2700: Negative selective pressure exerted by maintenance therapy promotes the extinction of sub-clones carrying high-risk lesions in multiple myeloma

BACKGROUND: Multiple Myeloma (MM) maintenance therapy is a low intensive, prolonged treatment, commonly administered to newly diagnosed patients (pts) at the end of front-line regimens. Lenalidomide (LEN) is considered the best available maintenance option for MM, the actual benefits or disadvantages of a LEN-based maintenance and its potential role as “selective pressure” on MM sublcones are still unclear. AIM: In this study we estimated the role of LEN maintenance therapy in eliciting genomic changes in a cohort of MM pts homogeneously up-front treated. PATIENTS-METHODS: Whole genome Copy Number Alterations (CNA) was obtained by SNPs array in 54 pts samples collected both at diagnosis(D) and at first relapse(R). Pts had an high-risk (HR) disease, defined by a median TTP of 29m. A custom gene-level CN calling algorithm was set up, to compute the evolution of every gene CN value and the genomic evolutive trajectories associated to changes of these values. High-risk genomic loci were defined using GISTIC to derive target genomic relevant for MM biology. After PIs induction therapy, 31/54 pts were treated with HD chemotherapy followed by either single or double ASCT; LEN maintenance therapy was then offered both to 20/31 auto-transplanted and to 6/23 not auto-transplanted pts. RESULTS: Three main evolutive trajectories (linear L, drift D, and branching B) were defined according to the CN changes9 direction, reflecting a putative positive, negative, or both positive and negative selective pressure, respectively. A fourth, stable (S) trajectory was also observed, characterized by the absence of CN changes. Overall, 29, 15 and 10 pts relapsed with B/D, L and S pattern, respectively; at R, all LEN-treated pts changed their sub-clonal architecture: a B/D evolutive pattern characterized 70% of pts. By contrast, genome remained mostly stable in 61% of not-treated pts. We then focused on CN changes of specific chromosomal regions and/or genomic loci identified as high-risk, whose prognostic role has been already established in MM (i.e. TP53, CDKN2C, CKS1B). When present at D, these CNA tended to persist throughout the disease course, regardless of whether pts received or not maintenance. The emersion of any of these CNAs at R was widely observed both in pts receiving or not maintenance, whereas a negative selective pressure over them was more likely to occur in pts receiving maintenance, as compared to the others (50% vs 11% of B/D trajectories in LEN-treated vs not-treated pts, respectively). Strikingly, in LEN-treated pts, the extension of both TTP and OS was favored by the extinction and/or negative selection (B/D patterns) of the HR CNAs, and shortened by their stability or positive selection (L/S patterns) (median TTP 46 vs 32m HR=3.6, p=0.01; median OS 111 vs 63m HR 5.7, p=0.04 in B/D vs L/S pts, respectively). On the contrary, the absence of maintenance selective pressure seemed to affect neither the evolution trajectory, nor the clinical course of not-treated pts. CONCLUSION: The extinction of sub-clones carrying HR lesions in pts receiving maintenance therapy is likely to be associated to the negative selection exerted by the therapy. This might explain the extended survival of these pts. On the contrary, the subclones of pts not receiving maintenance might randomly evolve, due to the absence of a specific selective pressure. Citation Format: Andrea Poletti, Vincenza Solli, Marina Martello, Enrica Borsi, Lucia Pantani, Agboyi Lakpo, Silvia Armuzzi, Luca Nunzio Cifarelli, Elena Zamagni, Paola Tacchetti, Serena Rocchi, Katia Mancuso, Ilaria Rizzello, Giulia Marzocchi, Nicoletta Testoni, Luca Dozza, Maria Teresa Petrucci, Anna Marina Liberati, Giuseppe Rossi, Mario Boccadoro, Michele Cavo, Carolina Terragna. Negative selective pressure exerted by maintenance therapy promotes the extinction of sub-clones carrying high-risk lesions in multiple myeloma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2700.