The frequency and clinical outcome of mono-hit and multi-hit TP53 aberrations in newly diagnosed multiple myeloma

We investigated the frequency and outcome of mono-hit and multi-hit TP53 aberrations [biallelic or ≥1 TP53 mutations (TP53mut) or TP53mut with variant allele frequency (VAF) ≥55%] in an Indian cohort of newly diagnosed multiple myeloma (NDMM) patients. We employed fluorescence insitu hybridisation (FISH; n=457) and targeted next-generation sequencing (NGS; n=244) on plasma cell-enriched samples. We also studied the impact of TP53mut in cases with and without TP53 deletions (TP53del). In our cohort with a median age of 60 years, TP53del and TP53mut were seen in 12.9% (n=59/457; 14-95% cells) and 10.2% (n=25/244; 30 variants; VAF 3.4-98.2%; median 38.2%) respectively. Mono-hit and multi-hit-TP53 aberrations were observed in 10.2% and 7.8%, respectively. Compared to TP53-wild-type (TP53wt), mono-hit and multi-hit TP53 aberrations were associated with significantly poorer progression-free survival (PFS) (22.6 vs 12.1 vs 9.5 months; p=0.004) and overall survival (OS) [not reached (NR) vs 13.1 vs 15.6 months respectively; p=0.024]. However, multi-hit TP53 did not significantly differ in OS/PFS compared to mono-hit cases. Compared to TP53wt, PFS and OS were significantly poorer in patients with TP53mut only (9.5 vs 22.6 months and 12.1 months vs NR, respectively; p=0.020/0.004). TP53mut retained its significance even in the presence of any Revised International Staging System (HR 2.1; 95% CI 1.1-3.8; p=0.015) for OS. The detection of additional cases with TP53 aberrations, as well as poor survival associated with the presence of mutation alone, supports TP53mut testing in NDMM at least in patients without TP53del and other high-risk cytogenetic abnormalities.