Tracking plasma KRAS mutations (mu) in lung adenocarcinoma (LUAC) patients (p) and branching evolution.

Abstract

9055 Background: KRAS m in LUAC p are recalcitrant to therapy. In mice models and p, STK11 m confer poor prognosis. Patients with KRAS, or KRAS with TP53 m, benefit from immunotherapy (IO). We used a cell free DNA (cfDNA) sequencing platform to sub-group 53 LUAC p with KRAS m from the Spanish Lung Liquid versus Invasive biopsy Program (SLLIP, NCT03248089), according to the coexistence of TP53 and STK11 m. We evaluated the treatment outcome in the KRAS subgroups and we explored the mutational evolution at 2 weeks (w), and at the end of the study (EOS). Methods: SLLIP was a multi-center observational study in patients with treatment-naïve metastatic LUAC. Genotyping, with a clinically validated cfDNA assay (Guardant360) was performed at 3 time points: before start of treatment, at 2 w, and upon progression or at 12 months (mo). Oncoprints were constructed based on mutation status and variant allele frequency (VAF). Results: 53 p with KRAS alterations were included. 36 male; median age 59; 46 current/ex-smokers; 64% received 1st line platinum-based chemotherapy (CT), 4% platinum-based CT+IO, 8% platinum-based CT plus bevacizumab, and 24% other or no therapy. 13 p had only KRAS m (K-only group), 25 p had KRAS + TP53 m (KP group), and 15 p had KRAS + STK11 with or without TP53 m (KS group). Median progression-free survival was 3.5 mo for all 53 p, 4.8 mo for the K-only group, 4.4 mo for the KP group, and only 2.6 mo for the KS group (p = 0.05 for KS versus K-only). The average VAF for K-only, KP, and KS groups at EOS were 6.4%, 9.7%, and 46%, respectively. When looking at p with cfDNA analysis at the three time points, the following were observed: In the K-only group, 25% lost KRAS m at 2 w and 50% at EOS. 50% and 75% gained TP53 m, at 2 w and EOS, respectively. None gained STK11 at the 2 time points. In the KP group, 40% lost KRAS m at 2 w but all had KRAS m at EOS. 20% and 10% lost TP53 m, at 2 w and EOS, respectively. 10% gained STK11 m at the 2 time points. In the KS group, 33% lost KRAS m at the 2 time points. All and 33% lost STK11 m at 2 w and EOS, respectively. 66% gained TP53 at the 2 time points. Conclusions: Subgroups of KRAS m traced in cfDNA confirm dismal prognosis to 1st line therapies. These findings prompt us to tailor IO for K-only or KP subgroups. For p with STK11 m, restoration of the STK11 function is warranted. Clinical trial information: NCT03248089.