Association between TP53 gain of function and loss of function mutational subgroups and survival in pancreatic adenocarcinoma.

Abstract

694 Background: TP53 is a commonly mutated tumor suppressor in pancreatic adenocarcinoma (PDAC) but the clinical implications for different classes of TP53 variants remain unclear. In contrast to loss of function (LOF) mutations, TP53 gain of function (GOF) mutations alter DNA conformational binding (e.g. R175H, G245S, R249S, R282H) or modify DNA contact hotspots (e.g. R248Q, R248W, R273H) and are associated with aggressive phenotypes. Here, we analyze progression-free survival (PFS) on standard therapies and overall survival (OS) of PDAC patients (pts) within TP53 mutational subgroups: GOF, LOF, and wild type (WT). Methods: We analyzed longitudinal outcomes across 775 pts with next generation DNA sequencing (NGS) results from Perthera’s Real-World Evidence database who received at least 1 line of therapy in the advanced setting for PDAC. PFS was evaluated from initiation of 1st line for advanced disease until discontinuation. Hazard ratios and p-values were computed via Cox regression when comparing OS relative to date of advanced diagnosis and PFS on subsets who received 1st line FOLFIRINOX (FFX) or 1st line gemcitabine/nab-paclitaxel (GA). Differences in frequencies of genomic alterations between TP53 mutational subgroups were analyzed by Fisher’s exact test. Results: In the TP53 LOF subgroup, median PFS on 1st line GA was significantly worse than 1st line FFX (Table) but this difference was not observed in TP53 GOF or WT subgroups. Irrespective of 1st line therapy choice, median OS in the WT subgroup (2.1y [1.8-2.4]) was significantly longer (p<0.05) than pts with TP53 GOF (1.5y [1.3-2.1]) or TP53 LOF (1.4y [1.3-1.5]). KRAS mutations were enriched (unadjusted p<0.05) for co-occurrence with TP53 in GOF (93.7%) and LOF (93.3%) subgroups relative to WT (74.5%). Mutations in BRCA1/2 were less common in the TP53 GOF subgroup (2.5%) relative to LOF (5.1%) and WT (11.6%). ATM mutations as well as an expanded set of genomic alterations within the DDR pathway were also enriched with similar trends (GOF<LOF<WT). Other potentially confounding factors will be discussed in the context of multivariate OS/PFS analyses. Conclusions: TP53 mutations correlated with worse prognosis in advanced PDAC. Potential predictive associations favoring FFX over GA in the TP53 LOF subgroup (but not in GOF or WT subgroups) warrant further exploration. [Table: see text]