Examining TP53-mutated plasma cell disorders across the disease spectrum using broad next generation sequencing

Abstract TP53 is the most frequently mutated gene in human cancer. Loss-of-function mutations or deletions of chromosome 17p are strongly associated with aggressive disease, resistance to therapy, and poor clinical outcomes across multiple cancers, including plasma cell disorders (PCDs). In multiple myeloma (MM), TP53 mutations are present in 5–10% of cases, with higher prevalence in advanced or relapsed disease, and predict for inferior survival. Recent large-scale genomic studies have highlighted the extensive genetic heterogeneity of MM where comprehensive sequencing efforts have underscored the need for detailed genomic profiling to inform risk stratification and guide personalized therapy. The clinical utility of TP53 testing in other PCDs is less established. In smoldering multiple myeloma (SMM), TP53 alterations are under investigation as markers for progression risk and early intervention strategies. In Waldenström macroglobulinemia (WM), light-chain amyloidosis (AL), and POEMS syndrome, TP53 mutations are rare and currently lack a defined clinical role. Next-generation sequencing (NGS) is used to detect TP53 mutations, assess variant allele frequency (VAF), and identify co-occurring driver mutations and variants of unknown significance (VUS). NGS is increasingly applied to guide prognosis and therapeutic decision-making in PCDs. This study aims to determine whether TP53-mutated samples in a PCD cohort exhibit a higher number of subclonal mutations (VAF<10%) and VUS identified by NGS, and to characterize the identified TP53 mutations. There were 252 DNA samples collected; 228 from bone marrow, 5 from tissue, and 19 from peripheral blood, including 84 MGUS, 23 SMM, 102 MM, 14 AL, and 29 other types (solitary plasmacytoma, POEMS, and WM). Diagnosis was verified by chart review. Samples were sequenced using the Tempus xT® 648-gene panel and included PCD cases from January 2020 through May 2025. Programs used in analysis included Python 3 (Jupyter v7.3.2) and Excel (v16.96.1). COSMIC (v102) and The TP53 Database (vR21) web platforms were used to assess cancer association and mutation characteristics. By disease, 5 MGUS, 2 SMM, 13 MM, and 1 WM sample harbored TP53 mutations, comprising 8.3% of all samples. There were 4 concurrent 17p deletions and 4 more cases with deletions alone identified by karyotype and/or FISH, all of which were MM. Three samples lacked karyotype or FISH data. All but one mutation were classified as either potentially actionable (2) or biologically relevant (20); the single VUS identified (c.871A>G) from MM remission marrow has been previously reported in non-PCD malignancies based on cross-referencing with COSMIC. Recurrent mutations included c.742C>T and c.814G>A, in two samples each, from different patients and diseases; and c.991C>T, which was present in 4 samples from a single patient with MM progressed to plasma cell leukemia. Compared to wild type, TP53-mutated samples demonstrated a significantly higher total number of mutations, inclusive of oncogenic and VUS (mean=4.97 vs 10.43, respectively; p=0.0073, Welch's one-way t-test), and VUS alone (mean=4.11 vs 7.67; p=0.0345). There was not a significant difference in the number of subclonal gene mutations (mean=1.84 vs 3.48; p=0.0808). Of 23 TP53 mutations, 18 of which were unique, 15 were located in the DNA binding domain of TP53 within exons 4 (n=1), 5 (n=7), 6 (n=1), 7 (n=3) and 8 (n=3). 15 were located in known cancer hotspots, and 14 were missense mutations. Eleven were transactivation non-functional and known to be damaging by SIFT. The only identified VUS was both functional and tolerated. TP53-mutated samples had a significantly greater number of genetic changes including total mutations and VUS alone, and our findings support the hypothesis that TP53 mutation status is associated with increased genomic complexity. Although our findings did not support association with subclonal diversification, data was limited by sample size and trended towards a greater number of subclonal mutations in the TP53-mutated cohort. The majority of TP53 mutations were missense mutations localized in the DNA binding domain, a finding reflected in current literature. The prognostic value of TP53 mutation is well studied, however further studies are required to better characterize co-occurring mutations. Our data suggests utility in co-assessment with NGS and highlights the need for continued refinement of NGS-based risk stratification tools in PCDs.