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C.T. Chu
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MA04 - HER2, P53, KRAS and Other Targets in Advanced NSCLC (ID 380)
- Event: WCLC 2016
- Type: Mini Oral Session
- Track: Advanced NSCLC
- Presentations: 1
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MA04.07 - Impact of Major Co-Mutations on the Immune Contexture and Response of KRAS-Mutant Lung Adenocarcinoma to Immunotherapy (ID 6343)
16:42 - 16:48 | Author(s): C.T. Chu
- Abstract
- Presentation
Background:
Activating mutations in the KRAS proto-oncogene define a prevalent and clinically heterogeneous molecular subset of lung adenocarcinoma (LUAC). We previously identified three major subgroups of KRAS-mutant LUAC on the basis of co-occurring genetic events in TP53 (KP), STK11/LKB1 (KL) and CDKN2A/B (KC) and reported that LKB1-deficient tumors exhibit a “cold” tumor immune microenvironment, with reduced expression of several immune checkpoint effector/mediator molecules, including PD-L1 (CD274). Here, we extend these findings and examine the clinical outcome of co-mutation defined KRAS subgroups to therapy with immune checkpoint inhibitors.
Methods:
We conducted a single-institution analysis of clinical and molecular data (PCR-based next generation sequencing of panels of 50, 134 or 409 genes) prospectively collected from patients enrolled into the MD Anderson Lung Cancer Moon Shot GEMINI database. KRAS-mutant LUAC were separated into KP, KL and K (wild-type for TP53 and STK11) groups. The log- rank test and Fisher’s exact test were used for comparison of progression-free survival (PFS) and objective response rate (ORR) respectively between the groups. In addition, automated IF-based enumeration of lymphocyte subsets was performed in 40 surgically resected LUAC (PROSPECT cohort) with available whole exome sequencing data.
Results:
Among 229 patients with KRAS-mutant LUAC who consented to the protocol we identified 35 patients with metastatic disease (17 KP, 6 KL, 12 K) that received immunotherapy with nivolumab (N=29), pembrolizumab (N=3), nivolumab/urelumab (N=1) and durvalumab/tremelimumab (N=2) and had robust clinical outcome data. There was no impact of different KRAS alleles (G12C/G12V/G12D) on PFS (P=0.6149, log-rank test) or ORR to immune checkpoint inhibitors (P=0.88, Fisher’s exact test, 2x3 contingency table). In contrast, co-mutation defined KRAS subgroups exhibited significantly different median PFS to immunotherapy (KP: 18 weeks, KL: 6 weeks, K: 16 weeks, P=0.0014, log-rank test). Objective responses were observed in 9/17 (52.9%) KP and 3/12 (25%) K tumors compared to 0/6 (0%) KL tumors (P=0.049, Fisher’s exact test, 2x3 contingency table). In the PROSPECT cohort of surgically resected LUACs with available whole exome sequencing data, somatic mutation in STK11 was associated with reduced intra-tumoral densities of CD3+ (P=0.0016), CD8+ (P=0.0125) and CD4+ (P=0.0036) lymphocytes.
Conclusion:
Mutations in STK11/LKB1 are associated with an inert tumor immune microenvironment and poor clinical response of KRAS-mutant LUAC to immune checkpoint blockade. The mechanism that underlies this phenotype and strategies to overcome it are under investigation. The impact of additional co-mutations on the immune profile and response of KRAS-mutant LUAC to immunotherapy is also being explored.
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