KRAS is the most common oncogenic driver in lung adenocarcinoma (LUAC). We previously reported that STK11/LKB1 (KL) or TP53 (KP) comutations define distinct subgroups of KRAS-mutant LUAC. Here, we examine the efficacy of PD-1 inhibitors in these subgroups. Objective response rates to PD-1 blockade differed significantly among KL (7.4%), KP (35.7%), and K-only (28.6%) subgroups (P < 0.001) in the Stand Up To Cancer (SU2C) cohort (174 patients) with KRAS-mutant LUAC and in patients treated with nivolumab in the CheckMate-057 phase III trial (0% vs. 57.1% vs. 18.2%; P = 0.047). In the SU2C cohort, KL LUAC exhibited shorter progression-free (P < 0.001) and overall (P = 0.0015) survival compared with KRAS^MUT;STK11/LKB1^WT LUAC. Among 924 LUACs, STK11/LKB1 alterations were the only marker significantly associated with PD-L1 negativity in TMB^{Intermediate/High} LUAC. The impact of STK11/LKB1 alterations on clinical outcomes with PD-1/PD-L1 inhibitors extended to PD-L1–positive non–small cell lung cancer. In Kras-mutant murine LUAC models, Stk11/Lkb1 loss promoted PD-1/PD-L1 inhibitor resistance, suggesting a causal role. Our results identify STK11/LKB1 alterations as a major driver of primary resistance to PD-1 blockade in KRAS-mutant LUAC. Significance: This work identifies STK11/LKB1 alterations as the most prevalent genomic driver of primary resistance to PD-1 axis inhibitors in KRAS-mutant lung adenocarcinoma. Genomic profiling may enhance the predictive utility of PD-L1 expression and tumor mutation burden and facilitate establishment of personalized combination immunotherapy approaches for genomically defined LUAC subsets. Cancer Discov; 8(7); 822–35. ©2018 AACR. See related commentary by Etxeberria et al., p. 794. This article is highlighted in the In This Issue feature, p. 781

Considering retreatment following recovery from an immune-related adverse event (irAE) is a common clinical scenario, but the safety and benefit of retreatment is unknown. We identified patients with advanced non–small cell lung cancer (NSCLC) treated with anti-PD-(L)1 who had treatment held due to irAEs and divided them into two groups: those retreated with anti-PD-(L)1 (retreatment cohort) or those who had treatment stopped (discontinuation cohort). Out of 482 NSCLC patients treated with anti-PD-(L)1, 68 (14%) developed a serious irAE requiring treatment interruption. Of these, 38 (56%) were retreated and 30 (44%) had treatment discontinued. In the retreatment cohort, 18 (48%) patients had no subsequent irAEs, 10 (26%) had recurrence of the initial irAE, and 10 (26%) had a new irAE. Most recurrent/new irAEs were mild (58% grade 1–2) and manageable (84% resolved or improved to grade 1). Two treatment-related deaths occurred. Recurrent/new irAEs were more likely if the initial irAE required hospitalization, but the initial grade and time to retreatment did not influence risk. Among those with no observed partial responses prior to the irAE, progression-free survival (PFS) and overall survival (OS) were longer in the retreatment cohort. Conversely, for those with objective responses prior to the irAE, PFS and OS were similar in the retreatment and discontinuation cohorts. Among patients with early objective responses prior to a serious irAE, outcomes were similar, whether or not they were retreated. Together, data suggest that benefit may occur with retreatment in patients with irAEs who had no treatment response prior to irAE onset. Cancer Immunol Res; 6(9); 1093–9. ©2018 AACR.

NRG1 rearrangements are oncogenic drivers that are enriched in invasive mucinous adenocarcinomas (IMA) of the lung. The oncoprotein binds ERBB3–ERBB2 heterodimers and activates downstream signaling, supporting a therapeutic paradigm of ERBB3/ERBB2 inhibition. As proof of concept, a durable response was achieved with anti-ERBB3 mAb therapy (GSK2849330) in an exceptional responder with an NRG1-rearranged IMA on a phase I trial (NCT01966445). In contrast, response was not achieved with anti-ERBB2 therapy (afatinib) in four patients with NRG1-rearranged IMA (including the index patient post-GSK2849330). Although in vitro data supported the use of either ERBB3 or ERBB2 inhibition, these clinical results were consistent with more profound antitumor activity and downstream signaling inhibition with anti-ERBB3 versus anti-ERBB2 therapy in an NRG1-rearranged patient-derived xenograft model. Analysis of 8,984 and 17,485 tumors in The Cancer Genome Atlas and MSK-IMPACT datasets, respectively, identified NRG1 rearrangements with novel fusion partners in multiple histologies, including breast, head and neck, renal, lung, ovarian, pancreatic, prostate, and uterine cancers. Significance: This series highlights the utility of ERBB3 inhibition as a novel treatment paradigm for NRG1-rearranged cancers. In addition, it provides preliminary evidence that ERBB3 inhibition may be more optimal than ERBB2 inhibition. The identification of NRG1 rearrangements across various solid tumors supports a basket trial approach to drug development. Cancer Discov; 8(6); 686–95. ©2018 AACR. See related commentary by Wilson and Politi, p. 676. This article is highlighted in the In This Issue feature, p. 663

Purpose: KRAS mutations are identified in approximately 30% of patients with non–small cell lung cancer (NSCLC). Novel direct inhibitors of KRAS G12C have shown activity in early-phase clinical trials. We hypothesized that patients with KRAS G12C mutations may have distinct clinical characteristics and responses to therapies. Experimental Design: Through routine next-generation sequencing, we identified patients with KRAS-mutant NSCLC treated at Memorial Sloan Kettering Cancer Center (New York, NY) from 2014 to 2018 and reviewed tumor characteristics, overall survival, and treatment outcomes. Results: We identified 1,194 patients with KRAS-mutant NSCLC, including 770 with recurrent or metastatic disease. KRAS G12C mutations were present in 46% and KRAS non-G12C mutations in 54%. Patients with KRAS G12C had a higher tumor mutation burden (median, 8.8 vs. 7 mut/Mb; P = 0.006) and higher median PD-L1 expression (5% vs. 1%). The comutation patterns of STK11 (28% vs. 29%) and KEAP1 (23% vs. 24%) were similar. The median overall survivals from diagnosis were similar for KRAS G12C (13.4 months) and KRAS non-G12C mutations (13.1 months; P = 0.96). In patients with PD-L1 ≥50%, there was not a significant difference in response rate with single-agent immune checkpoint inhibitor for patients with KRAS G12C mutations (40% vs. 58%; P = 0.07). Conclusions: We provide outcome data for a large series of patients with KRAS G12C–mutant NSCLC with available therapies, demonstrating that responses and duration of benefit with available therapies are similar to those seen in patients with KRAS non-G12C mutations. Strategies to incorporate new targeted therapies into the current treatment paradigm will need to consider outcomes specific to patients harboring KRAS G12C mutations.

Purpose: Treatment with PD-(L)1 blockade can produce remarkably durable responses in patients with non–small cell lung cancer (NSCLC). However, a significant fraction of long-term responders ultimately progress and predictors of late progression are unknown. We hypothesized that circulating tumor DNA (ctDNA) analysis of long-term responders to PD-(L)1 blockade may differentiate those who will achieve ongoing benefit from those at risk of eventual progression. Experimental Design: In patients with advanced NSCLC achieving long-term benefit from PD-(L)1 blockade (progression-free survival ≥ 12 months), plasma was collected at a surveillance timepoint late during/after treatment to interrogate ctDNA by Cancer Personalized Profiling by Deep Sequencing. Tumor tissue was available for 24 patients and was profiled by whole-exome sequencing (n = 18) or by targeted sequencing (n = 6). Results: Thirty-one patients with NSCLC with long-term benefit to PD-(L)1 blockade were identified, and ctDNA was analyzed in surveillance blood samples collected at a median of 26.7 months after initiation of therapy. Nine patients also had baseline plasma samples available, and all had detectable ctDNA prior to therapy initiation. At the surveillance timepoint, 27 patients had undetectable ctDNA and 25 (93%) have remained progression-free; in contrast, all 4 patients with detectable ctDNA eventually progressed [Fisher P < 0.0001; positive predictive value = 1, 95% confidence interval (CI), 0.51–1; negative predictive value = 0.93 (95% CI, 0.80–0.99)]. Conclusions: ctDNA analysis can noninvasively identify minimal residual disease in patients with long-term responses to PD-(L)1 blockade and predict the risk of eventual progression. If validated, ctDNA surveillance may facilitate personalization of the duration of immune checkpoint blockade and enable early intervention in patients at high risk for progression.