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e23419 Background: Current risk assessment for cancer-associated thrombosis remain suboptimal in NSCLC, likely due to unaccounted tumor-specific biology. Although ALK and ROS1-positive NSCLC share closely related structure and elevated thrombotic risk, real-world data on thromboembolic outcomes remain limited. Methods: This multicenter retrospective study was conducted using TriNetX, a global federated health research network;14 of 113 healthcare organizations contributed to analysis. Adults (≥18 years) with NSCLC ROS1 or ALK from 2012-2025 were included. Index event was defined as the first documented NSCLC diagnosis. Outcomes included cumulative incidence, Kaplan–Meier survival analysis (KMS), and event recurrence for arterial thromboembolism (ATE), deep vein thrombosis (DVT), and pulmonary embolism (PE). Analyses were conducted pre and post-propensity score matching (PSM) adjusted for age and sex. Subgroup analyses evaluated outcomes at 1, 3, 6, and ≥12 months. Results: 3,310 NSCLC patients were identified (ALK n=3,155; ROS1 n=155). Mean age was 73 years, with 52.8% female and 46.2% male; 72.5% White, 12.7% Black, 9.5% Asian; South (49%), Northeast (29%). ALK NSCLC were older than those with ROS1 (mean 68.9 vs 64.6 years, p<0.0001), with similar sex distribution. ROS1 had higher proportion of White (85% vs 72%), while ALK included more Asian and Black. Median follow-up prior to matching was 482 days for ROS1 (post-PSM:482) and 546 days for ALK (post-PSM:601) Incidence proportions in ROS1 NSCLC were 12.3% for ATE, 9.7% for DVT, and 12.9% for PE (vs. ALK: 22.6% for ATE, 12.5% for DVT, 11.8% for PE) For ATE, prior to PSM, ROS1 NSCLC demonstrated a significantly lower risk compared with ALK (16.6% vs 25.0%), with an absolute risk difference of −8.4% (95% CI −14.7 to −2.2; p=0.02) and relative risk of 0.66 (95% CI 0.46–0.96). KMS showed longer ATE-free survival in ROS1 compared to ALK (48.2% vs 44.5%, p=0.01; HR 0.60, 95% CI 0.40–0.91, p=0.04). After PSM, overall ATE risk difference did not reach statistical significance, although ROS1 continued to demonstrate lower risk (16.6% vs 25.8%; risk difference −9.2%, p=0.06). Notably, in the subgroup analyses, this significant risk difference emerged ≥12 months, with improved late ATE-free survival in ROS1(91.1% vs 80.3%, p=0.01). For VTE and PE, no significant differences in risk, survival analyses or recurrence, were observed between ROS1 and ALK before or after PSM (DVT risk: 9.2% vs 9.7% pre-PSM; 9.2% vs 10.1% post-PSM; PE: 11.2% vs 9.9% pre-PSM; 11.2% vs 8.6% post-PSM; all p>0.05). Conclusions: Arterial thromboembolism differed by oncogenic subtype, with higher ATE risk in ALK compared with ROS1-positive NSCLC, particularly ≥12-months. In contrast, no significant difference in venous thromboembolism and pulmonary embolism were observed; further validation in prospective studies is warranted.

Abstract Introduction Bronchiectasis is a chronic respiratory disease that increases fatigue, disability, and impairs quality of life. However, the impact of fatigue on patients with bronchiectasis, even in short-term follow-up, has not been sufficiently examined. We explored the association between fatigue and clinical outcomes among patients with bronchiectasis. Methods Adult bronchiectasis patients enrolled in the US Bronchiectasis and Nontuberculous Mycobacteria Research Registry were retrospectively analyzed. Patients with at least one annual follow-up visit in the 3-5 years post baseline and with fatigue data at both baseline and follow-up were included. Patients were grouped as experiencing fatigue versus not experiencing fatigue in the 2-years prior to baseline as reported at their baseline visit. We explored the relationship between baseline fatigue with patient demographics, co-existing conditions, components of the modified bronchiectasis severity index at baseline and follow-up. Wilcoxon, chi-square, and Fisher’s exact tests were used to assess the differences in continuous variables and associations between categorical variables, respectively. Stepwise multivariable logistic regression models explored the relationship of baseline fatigue with exacerbations and hospitalizations at follow-up. Model selection predictors were evaluated based on clinical relevance or p &lt; 0.05 in univariable analyses. Results 1265 adults with bronchiectasis met the inclusion criteria. 563(45%) reported experiencing fatigue and 702 (55%) did not. The median age (interquartile range) was 70(62-78) years and patients were predominantly female (n = 1042, 83%). At baseline, patients experiencing fatigue had a higher proportion of co-existing diagnoses such as gastroesophageal reflux disease, chronic obstructive pulmonary disease, and rheumatologic disease, compared to those without fatigue (all p &lt; 0.05). Furthermore, patients with fatigue had a higher prevalence of pulmonary-related hospitalizations (p &lt; 0.001) at baseline and follow-up. Pseudomonas aeruginosa colonization and elevated dyspnea (modified Medical Research Council [mMRC] grade≥1) were more prevalent among those experiencing baseline fatigue compared to those without (all, p &lt; 0.05). History of prior exacerbations (Odds Ratio [OR]:1.67, 95% CI:1.17-2.41) and baseline Pseudomonas aeruginosa colonization (OR:1.22, 95% CI:1.01-1.47) were significantly associated with increased odds of exacerbations at follow-up. In multivariable stepwise logistic regression, there was an increased odds of at least 1-hospitalization at follow-up among males (OR:2.23, 95% CI 1.12-4.42), patients with decreased Body Mass Index (OR:0.93, 95% CI: 0.87-1.0), and among patients with elevated dyspnea (mMRC grade ≥1) at baseline (OR:2.22, 95% CI: 1.16-4.24),[Table 1]. Conclusions Fatigue in bronchiectasis patients is associated with a more severe disease and greater healthcare utilization, although it may not independently predict future exacerbations or hospitalizations when accounting for other factors. This abstract is funded by: Bronchiectasis and NTM Association

Abstract Purpose: Rearranged during transfection (RET) alterations are oncogenic drivers across solid tumors. Selective RET inhibitors (SRI) selpercatinib and pralsetinib have transformed outcomes for patients with RET-altered malignancies. Limited knowledge exists on genomic mechanisms of resistance to SRI. Experimental Design: We established “RETgistry,” a global consortium of patients with advanced RET-altered solid tumors who received SRI and underwent postprogression tissue or plasma biopsies assessed by next-generation sequencing. Frequencies of secondary RET resistance mutations and acquired non-RET gene alterations were determined. Progression-free survival (PFS) and time to treatment discontinuation (TTD) on first SRI were estimated with the Kaplan–Meier method. Results: RETgistry included 109 patients with RET-altered advanced solid tumors (lung, n = 94; thyroid, n = 15) who underwent 143 post-SRI progression biopsies (tissue, 91; plasma, 52). The median PFS and TTD were 13.9 months [95% confidence interval (CI), 10.1–16.6] and 17.3 months (95% CI, 14–20.2), respectively. Secondary RET mutations were detected in 20 (14%) biopsies [lung cancer, 15 (12.4%) and thyroid carcinoma, 5 (22.7%)]. Common acquired off-target alterations involved MET (18.2%; amplification, 15%), TP53 (8.2%), APC (7.6%), KRAS (7.1%), KEAP1 (5.9%), and CDKN2A/B (5.3%). MET alterations were enriched in post-SRI versus pre-SRI specimens (full cohort, 17.6% vs. 2.0%, P = 0.022; lung cancer, 19.1% vs. 2.1%, P = 0.022). Conclusions: The prevalence of secondary RET mutations after SRI was low, underscoring a greater role for off-target resistance. Recurrent acquired alterations involving tumor suppressor genes or upstream regulators of MAPK and PI3K pathways were identified, most commonly MET amplification. Continued efforts to characterize SRI resistance biology are critical to guide the development of novel therapeutic strategies.

8644 Background: RET fusions are targetable oncogenic drivers in 1-2% of non-small cell lung cancers (NSCLC). ARROW (NCT03037385) study results (final data lock May 20, 2024) supported the US FDA approval of pralsetinib, a highly potent, oral, selective RET inhibitor for metastatic RET -altered NSCLC. Here, we present final study results. Methods: ARROW was a phase 1/2 open-label study conducted at 84 sites in 13 countries. Phase 2 included patients with RET -fusion-positive NSCLC who received 400 mg pralsetinib once daily (QD). Initially, treatment-naïve patients were not candidates for platinum-based therapy and presented with several unfavorable prognostic factors; this requirement was removed by protocol amendment in July 2019. Primary objectives were overall response rate (ORR, per RECIST v1.1) and safety. Progression-free survival (PFS) and overall survival (OS) are reported in the full efficacy population; the measurable disease population (MDP) was the primary analysis population for ORR and duration of response (DOR). Results: 281 patients with RET -fusion-positive NSCLC received pralsetinib 400 mg QD, with a median duration of treatment of 14.95 months (mos). Median age was 60 years; 46% were male. In the MDP (n=259), ORR was 70.3% (95% confidence intervals [CI]: 64.3, 75.8) and median DOR was 19.1 mos (95% CI: 14.5, 27.9; Table). In the efficacy population (N=281), median OS was 44.3 mos (95% CI: 30.9, 53.1) with median follow up of 47.6 mos (95% CI: 44.8, 49.2), and median PFS was 13.1 mos (95% CI: 11.4, 16.8). ORR (Table) and median PFS were markedly higher in the US (25.9 mos, n=64) vs. Asia (12.6 mos, n=122) or Europe (12.9 mos, n=95). In the safety population, 95% of patients experienced treatment-related adverse events (TRAEs); 66% experienced ≥grade 3. Common TRAEs included increased AST (n=128 [46%]), anemia (n=121 [43%]), increased ALT (n=98 [35%]), and hypertension (n=77 [27%]). 3 patients died due to TRAEs (pneumonia, n=2; interstitial lung disease and rhabdomyolysis, n=1 each). No new safety signals were identified with this update. Conclusions: Pralsetinib produced clinically meaningful and durable responses in patients with RET -fusion-positive NSCLC (regardless of prior therapies) with a manageable safety profile, confirming with this longer follow up previously published results. Clinical trial information: NCT03037385 . All MDP(n=259) Prior Platinum (n=130) Treatment-naive(n=106) ORR, % (95% CI) Overall 70.3(64.3, 75.8) 63.1(54.2, 71.4) 78.3(69.2, 85.7) US (n=58)77.6(64.7, 87.5) (n=31)64.5(45.4, 80.8) (n=19)100(82.4, 100) Europe (n=89)65.2(54.3, 75) (n=36)63.9(46.2, 79.2) (n=43)65.1(49.1, 79) Asia (n=112)70.5(61.2, 78.8) (n=63)61.9(48.8, 73.9) (n=44)81.8(67.3, 91.8) Median DOR, mos (95% CI) a (n=182)19.1(14.5, 27.9) (n=82)31.8(15.1, 40.4) (n=83)13.4(9.4, 21.7) Median DOR follow up, mos (95% CI) 46.8(42.3, 50.2) 50.3(46.9, 56.8) 42.3(37.4, 44.2) a Per FDA censoring rule.

Abstract Introduction Persistent dyspnea increases the risk of disability and impairs quality of life in older patients with bronchiectasis. The impact of dyspnea and fatigue on patients with bronchiectasis in long term follow-up has not been adequately established. We sought to determine if fatigue and higher-grade dyspnea are associated with worse clinical outcomes in 5-years of longitudinal follow-up. Methods We analyzed data collected from a prospective cohort of adult patients with bronchiectasis enrolled in the US Bronchiectasis and Nontuberculous Mycobacteria Research Registry. Patients with a modified Medical Research Council (mMRC) dyspnea score collected at baseline and during 3-5 years of follow-up were included and stratified as mMRC&lt;2 versus mMRC ≥2. Kruskal-Wallis, independent sample t-tests and chi-square tests were used to test the differences in medians and means for continuous variables and associations between categorical variables, respectively, between the baseline mMRC groups and bronchiectasis severity index (BSI) components at follow-up. A multivariable logistic regression analysis was performed to determine the association between dyspnea and clinical outcomes (exacerbations and hospitalizations) at follow-up. Results 1185 adult patients with bronchiectasis met the inclusion criteria. The median age (interquartile range) was 76 (68 to 83) years. At baseline, patients with mMRC ≥2 had a higher proportion of co-existing diagnoses such as asthma, chronic obstructive pulmonary disease (COPD), otitis/rhinosinusitis, rheumatologic disease, and pneumonia compared to patients with mMRC &lt;2 (all p&lt;0.05, data not shown). Furthermore, patients with mMRC &gt; 2 compared to patients with mMRC &lt;2 had higher prevalence of fatigue, acute exacerbations and pulmonary related hospitalizations, and lower mean percentage predicted forced expiratory volume in one second (FEV1) at follow-up (all p&lt; 0.05) (Table 1). Interestingly, body mass index was slightly higher among those with baseline mMRC ≥2 compared to mMRC &lt;2 (p=0.02). Among those with mMRC ≥2 at both baseline and follow-up (n=67, 42%), the odds of having ≥1 exacerbation was 2.4 times higher (odds ratio [OR] 2.45, 95% confidence interval [CI] 1.45-4.1) and 2.8 times higher for ≥1 hospitalization (OR 2.8, 95% CI 1.45-5.2) during follow-up after adjusting for fatigue. Conclusion Elevated dyspnea was associated with a greater proportion of patients with bronchiectasis exhibiting acute exacerbations and pulmonary related hospitalizations and lower lung function during follow-up. Research is still needed to understand the causes (drivers) of dyspnea to implement better treatment strategies and reduce adverse outcomes in bronchiectasis patients.

Abstract Introduction: Non-Cystic Fibrosis Bronchiectasis (NCFB) is an obstructive pulmonary disease associated with structural lung disease, altered mucociliary clearance, hyper mucus secretion, recurrent infection, and airway inflammation that results in significant morbidity and mortality. Aspergillus sp (Asp) is a common fungi isolated in respiratory specimens of those with lung disease and is associated with both infectious and allergic pulmonary diseases such as Asthma and Cystic Fibrosis. Despite individuals with NCFB having similar phenotypes as these conditions, the impact of Asp on this population is poorly understood. Methods: We performed a cross-sectional retrospective analysis from the US Bronchiectasis and NTM Research Registry (BRR). NCFB patients without a history of lung transplant who had at least one respiratory Asp culture were included. We compared patients with no history of Asp grown from respiratory culture to those with at least one positive respiratory culture for Asp during the available period. Patient demographics, bacterial culture history, lung function, comorbidities, modified Bronchiectasis Severity Index (mBSI), and sputum parameters were analyzed descriptively. Comparisons between groups were conducted using Kruskal-Wallis, independent sample t-tests, and chi-square tests for continuous and categorical variables as appropriate. Results: 3985 people with NCFB met inclusion criteria. 3359 (84.3%) individuals were Asp culture negative compared to 626 (15.7%) individuals with Asp. There were notable differences in race, showing higher proportions of non-Hispanic white (90.4 vs 82.2%) in this population. While the frequency of Chronic Obstructive Pulmonary Disease and Primary Ciliary Dyskinesia were similar, there were more individuals with Asthma (31.3 vs 24.7%, p&lt;0.001) and Allergic Bronchopulmonary Aspergillosis (ABPA) (6.4 vs 2.4%, p&lt;0.001) in the Asp positive group (Figure 1A). The Asp positive group had higher blood eosinophils (150.0 vs 124.0 cells/uL, p=0.026, Figure 1B), had nominally lower lung function (73.5 vs 75.3% ppFEV1, p=0.089), and were more likely to have at least one or more positive bacterial cultures (62.9 vs 51.9%, p&lt;0.001, Figure 1C). There was no significant difference in sex, age, exacerbations, Pseudomonas aeruginosa or NTM positive cultures, sputum volume, or mBSI. Conclusion: Individuals with NCFB and history of one or more positive Asp cultures were more likely to be non-Hispanic white, have a diagnosis of Asthma and/or ABPA, higher blood eosinophils, and more positive airway bacterial cultures. Further work is needed to better understand how Asp contributes to bronchiectasis progression. More expansive analysis and multivariant modeling is underway to better understand the impact of Asp in people with NCFB.

Abstract Purpose: Non-invasive monitoring of circulating tumor DNA (ctDNA) has the potential to be a readily available measure for early prediction of clinical response. Here, we report on early ctDNA changes of KRAS G12C in a Phase 2 trial of adagrasib in patients with advanced, KRAS G12C-mutant lung cancer. Experimental Design: We performed serial droplet digital PCR (ddPCR) and plasma NGS on 60 KRAS G12C-mutant patients with lung cancer that participated in cohort A of the KRYSTAL-1 clinical trial. We analyzed the change in ctDNA at 2 specific intervals: Between cycles 1 and 2 and at cycle 4. Changes in ctDNA were compared with clinical and radiographic response. Results: We found that, in general, a maximal response in KRAS G12C ctDNA levels could be observed during the initial approximately 3-week treatment period, well before the first scan at approximately 6 weeks. 35 patients (89.7%) exhibited a decrease in KRAS G12C cfDNA &gt;90% and 33 patients (84.6%) achieved complete clearance by cycle 2. Patients with complete ctDNA clearance at cycle 2 showed an improved objective response rate (ORR) compared with patients with incomplete ctDNA clearance (60.6% vs. 33.3%). Furthermore, complete ctDNA clearance at cycle 4 was associated with an improved overall survival (14.7 vs. 5.4 months) and progression-free survival (HR, 0.3). Conclusions: These results support using early plasma response of KRAS G12C assessed at approximately 3 weeks to anticipate the likelihood of a favorable objective clinical response.