MA04.05 P53 Non-Disruptive Mutation is a Negative Predictive Factor for OS and PFS in EGFR M+ NSCLC Treated with TKI

P53 mutations are common in lung cancer, and have also been described in EGFR mutated patients The impact of p53 mutations in EGFR M+ patients is controversial, especially if classified as “disruptive” and “non-disruptive” according to their functional effect on the p53 protein as proposed by Poeta and colleagues. The aim of the study was therefore to systematically analyze EGFR and p53 mutations within a cohort of patients with lung cancer stage IV (UICC 7), to correlate alterations with clinical characteristics and to investigate a potential impact of p53 mutations on treatment outcome. 484 patients diagnosed with lung cancer stage IV were studied for the presence of EGFR as well as inactivating p53 mutations. Methods for the detection of EGFR mutations included Sanger Sequencing and hybridization based COBAS testing, hybrid cage next generation sequencing. P53 mutations were detected by Sanger Sequencing and either Miseq or hybrid cage NGS. Clinical characteristics including smoking status were available for more than 97%. 484 consecutive patients were studied. The overall EGFR M+ rate was 17.8% (86/484) in all patients, 84.9% (73/86) showing common mutations of exon 19 or 21. In 21/86 (24.4%) patients’ p53 analysis was not successful. P53 disruptive mutations were demonstrated in 24.6% (16/65) of successfully tested patients, and p53 non-disruptive mutation occurred in 27.7% (18/65) whereas p53 WT configuration was found in 47.7% (31/65). Median OS was 28 months in p53 disruptive mutation and 44 month in p53 WT compared to 23 months in p53 non-disruptive mutation (p<0.023). PFS on 1st line TKI therapy was 14 months in p53 disruptive mutation, 27 months in p53 WT and 10 months in p53 non-disruptive mutation (p<0.040). Similar results were shown in the EGFR common mutation subgroup. 11/16 (68.8%) patients with a disruptive p53 M+ and 25/29 (86.2%) patients with a p53 WT constellation achieved an objective response on the 1st line TKI therapy compared to 7/13 (53.8%) patients with a non-disruptive p53 status. The patients with an unknown p53 status achieved an objective response on the 1st line TKI therapy of 82.4.8% (14/17). Significant differences in PFS and OS in EGFR M+ patients were observed depending on p53 M+ status. P53 mutational status is predictive when disruptive and non-disruptive p53 M+ are differentiated. A p53 WT constellation has a positive effect on OS and PFS. P53 should be tested prospectively in EGFR M+ patients as management of patients on 1st line TKI may be different.