Watson, Alexander

Abstract Pulmonary large cell neuroendocrine carcinoma (LCNEC) is a rare, aggressive lung tumor marked by significant molecular heterogeneity. In a study of 590 patients across two independent cohorts, we observed comparable overall survival across treatment regimens (chemotherapy, chemoimmunotherapy, immunotherapy) without unexpected adverse events. Genomic analysis identified distinct NSCLC-like (KEAP1, KRAS, STK11 mutations) and SCLC-like (RB1, TP53 mutations) LCNEC subtypes, with 80% aligning with SCLC transcriptional profiles. Serial sampling revealed stable mutational but shifting transcriptomic landscapes over time. NSCLC-like LCNECs showed elevated FGL-1 (a LAG-3 ligand) and SPINK1 expression, while SCLC-like subtypes expressed higher levels of DLL3. Immunofluorescence confirmed FGL-1 in NSCLC-like LCNECs, and H&E slide analyses indicated fewer tumor-infiltrating lymphocytes in LCNECs versus other lung cancers. These findings highlight LCNEC’s distinct immunogenomic profile, supporting future investigations into LAG-3, SPINK1, and DLL3-targeted therapies.

8106 Background: Due to lack of prospective data, the optimal first line treatment approach for patients (pts) with pure LCNEC histology remains uncertain. Methods: Across 17 centers, we conducted a retrospective analysis of metastatic pure LCNEC (diagnosed at local institutions) who received 1st-line systemic therapy between 2015-2023. Pts were either treated with chemotherapy (chemo), immunotherapy (IO), or a combination (chemoIO). Clinical outcomes were progression-free survival (PFS), overall survival (OS), objective response rates (ORR), and treatment-related adverse events (trAE) as defined using CTCAE 5.0. Survival analysis by genomic alteration status ( TP53, RB1, STK11, KEAP1, KRAS) and PD-L1 status were performed. Results: We identified 161 pts with median age of 67 years (IQR: 58-83) at 1st line systemic therapy; 54% (n = 87) were males. Median follow-up was 55 months (mo), 62 mo, and 29 mo for the chemo, IO, and chemoIO groups, respectively. 79% (n = 127) were former or current smokers. 1st-line treatments were chemo (n = 94), IO (n = 11), or chemoIO (n = 56). Of 85 pts with PD-L1 status, 58 (68%) were 0% and 27 (32%) were ≥1%. The most common chemo regimen was platinum-etoposide (n = 72, 78%). ChemoIO regimens included carboplatin/etoposide/atezolizumab (n = 23, 43%) and carboplatin/pemetrexed/pembrolizumab (n = 17, 31%). In the IO group, 1 patient received dual IO. Lung (n = 74, 46%) and liver (n = 71, 41%) were the most common sites of metastasisThere was no significant difference in PFS across the groups (median PFS [mPFS] chemoIO: 5.7 mo, 95% CI: 5.0-6.3, chemo: 5.1 mo, 95% CI: 3.1-5.9; IO: 3.6 mo, 95% CI: 1.7-6.5) on multivariable analysis adjusting for ECOG and “M” stage (p = 0.2 and 0.24 for chemoIO-chemo and chemoIO-IO comparisons, respectively). There was no difference in OS (mOS chemo: 11 mo, 95% CI: 7.6-17.4; IO: 13.6 mo, 95% CI: 5.9-not reached; chemoIO: 12.2 mo, 95% CI: 7.4-20.6, p = 0.5 and 0.8 for chemoIO-chemo and chemoIO-IO comparisons, respectively). ORR was 35.2% (31/88) in chemo, 25% (2/8) in IO, and 35.7% (20/56) in chemoIO ( p= 0.46). There were no significant differences in PFS and OS outcomes by treatment group when divided by genetic profile (n = 79, methods), or by PD-L1 status (0% vs ≥1%). Any grade trAE occurred in 48 (51%), 5 (45%), and 28 (50%) pts treated with chemo, IO, and chemoIO, respectively. Grade ≥3 toxicity profiles are shown (table). Conclusions: For 1st-line treatment of LCNEC, similar PFS, OS, and ORR were seen for chemo, IO, and chemoIO. This questions the added benefit of chemoIO compared to chemo alone, and warrants future clinical trials to discern the optimal 1st line treatment. [Table: see text]

8602 Background: LCNECs are a rare subtype of lung cancer, with limited clinical trial data and an unclear consensus on first-line treatment. Even less is known about the optimal treatment approach for pts with mixed LCNECs, a pathologic subtype where tumors contain both LCNEC histology as well as features of adenocarcinoma, squamous cell, or small cell lung cancer. Methods: We conducted an international multi-institutional retrospective analysis (n=13 institutions) of pts with advanced or metastatic mixed LCNECs who received 1st-line systemic therapy with either chemotherapy alone (chemo) or chemo-immunotherapy (chemoIO) between 2010-2023. Clinical outcomes included progression-free survival (PFS), overall survival (OS), objective response rate (ORR), and treatment-related adverse events (trAEs). Survival comparisons were made via the log-rank test. Results: Seventy-three pts with mixed LCNECs received either chemo (n=42, 57.5%) or chemoIO (n=31, 42.5%). The most common chemo regimens were carboplatin/etoposide (n=27) and cisplatin/etoposide (n=8), while the most common chemoIO was carboplatin/etoposide/atezolizumab (n=19). Median age at 1st-line therapy initiation was 65 (IQR: 60-72). 64% of pts were male (n=47). The majority were former smokers (n=41, 56.2%), with 22 current smokers (30.1%), and 10 non-smokers (13.7%). Mixed histologies included LCNEC/NSCLC (n=45, 56.2%), LCNEC/SCLC (n=17), LCNEC/carcinoid (n=1), and unspecified mixed LCNEC (n=10). Median PFS for chemo was 5 months (95% CI 2.7-9.2) vs. 6 months (95% CI 4.4-8.3) for chemoIO ( p=0.86). Median OS for chemo was 14.2 months (95% CI 10.4-22.5) vs. 17.2 months (95% CI 9.4-27.2) for chemoIO ( p=0.66). The ORR did not differ between chemo (n=18, 45%) and chemoIO (n=15, 48.4%) ( p=0.81). In the chemo group, 60% (n=25) experienced trAEs of any grade, with 23.8% (n=10) experiencing grade 3+ events and four requiring hospitalizations. For chemoIO pts, 61% (n=19) experienced trAEs, with 25.8% (n=8) experiencing grade 3+ events and six requiring hospitalizations. Neutropenia was the most common grade 3+ trAE for both chemo (n=5) and chemoIO (n=4). Overall, there were no significant differences between chemo or chemoIO groups for ORR ( p=0.81), all-grade trAEs ( p=0.88), grade 3+ trAEs ( p=0.84), PFS ( p=0.86), or median OS ( p=0.66). There were no significant differences in median PFS ( p=0.46) or OS ( p=0.99) for pts with mixed LCNEC/NSCLC vs. LCNEC/SCLC. Conclusions: For mixed LCNECs, there was no significant difference in PFS or OS between first-line treatment with chemo vs. chemoIO, suggesting limited benefit from immunotherapy for these pts. Additionally, survival outcomes did not differ between mixed LCNEC/NSCLC and LCNEC/SCLC, suggesting a biology primarily driven by their neuroendocrine component.