Abstract
8039 Background: Lung cancer is the leading cause of cancer-related deaths worldwide, and often presents at advanced stages, with > 50% of patients presenting as stage III or IV. Patients with recurrent stage III NSCLC (R/R) previously treated with definitive chemoradiation and immunotherapy consolidation may have a difference in overall survival compared to de novo stage IV (DN). In this study, we aim to compare the molecular and immune landscapes of these two patient populations to identify potential genomic patterns and biomarkers of resistance. Methods: 3728 NSCLC specimens underwent sequencing of DNA (592-gene panel or whole exome) or RNA (whole transcriptome) or immunohistochemistry at Caris Life Sciences (Phoenix, AZ). Patients were classified as R/R (n = 26) if they received Durvalumab and chemoradiation within 12 months (m) before tissue collection and treated with Pembrolizumab within 6 m after tissue collection. Patients treated with Pembrolizumab within 6 months after tissue collection and had no prior (or post) treatment with Durvalumab and chemoradiation at any point in time were classified as DN (n = 3702). Tumor microenvironment (TME) cell fractions were estimated from bulk RNA sequencing using QuanTIseq. Significance was determined using chi-square, Mann Whitney U and adjusted for multiple comparisons where applicable (q < 0.05). Results: TP53 (91 vs 68%) and KEAP1 (30 vs. 14%, both p < 0.05, q > 0.05) mutation prevalence was higher in R/R, whereas a decreased prevalence of KRAS mutations was noted in this group (13 vs. 33%) as compared to the DN group. Compared to DN patients, R/R patients were associated with an increased prevalence of mutations in BCL2 (4.3 vs. 0%, q < 0.05), BCL9 (4.3 vs. 0.2%, q < 0.05), HNF1A (4.3 vs. 0.2%), TNFAIP3 (4.3 vs. 0.2%), AKT1 (4.3 vs. 0.4%), MAP3K1 (4.3 vs. 0.5%), and SPEN (4.3 vs. 0.6%; all p < 0.05, q > 0.05). Further, copy number amplification of NUTM1 (4.5 vs. 0%), SMO (4.3 vs. 0.5%), CHIC2 (4.5 vs. 0.2%; all q < 0.05), PIK3CA (9 vs. 1.2%) and FLCN (4.5 vs. 0.3%; both p < 0.05, q > 0.05) was more common in R/R compared to DN. R/R TME was associated with decreased B cell (2.9 vs 4.4%, q < 0.05) and regulatory T cell fractions (1.3 vs. 2.6%, p < 0.05, q > 0.05). Conclusions: R/R patient tumors had distinct molecular alterations and immune landscapes, including an increased prevalence of biomarkers associated with immunotherapy resistance ( TP53 and KEAP1 mutations) and lower tumor B- and T reg- cell fractions, which may suggest decreased likelihood of response to immunotherapy compared to patients with DN NSCLC. The RR population had a lower-than-expected percentage of KRASmutations. These distinct molecular differences highlight the need for NGS testing in the recurrent setting, despite initial NGS testing at diagnosis. Molecularly targeted interventions may be options in the future for patients with R/R Stage III NSCLC.