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e16323 Background: Advanced EP-NEC are typically treated with the combination of platinum plus etoposide. Despite therapy, outcomes remain poor, with reported median overall survival (OS) of 12-13 months. Early initiation of systemic therapy is commonly practiced given the aggressiveness; however, recent data from small cell lung carcinoma (SCLC) suggest that shorter TTI does not necessarily improve OS. The impact of TTI on outcomes in EP-NEC has not been well studied. Methods: We conducted a multicenter retrospective cohort study across three Mayo Clinic sites including adults with biopsy-confirmed stage IV EP-NEC diagnosed between 2005 and 2025. TTI was defined as days from pathologic diagnosis to initiation of first-line systemic therapy. A binary cutoff (≤14 vs > 14 days) was determined using receiver operating characteristic (ROC) analysis, and TTI was also analyzed as a continuous variable. OS and progression-free survival (PFS) were estimated using the Kaplan–Meier method and evaluated using Cox proportional hazards models. Multivariable analyses adjusted for age, sex, ECOG performance status, presence of liver metastases, and first-line treatment strategy (chemotherapy alone vs chemotherapy plus immunotherapy). Results: Among 248 pts, median age was 61 years. Median OS for the cohort was 13.9 months (95% CI, 11.7–16.7), and median PFS was 5.7 months (95% CI, 5.3–6.3). Pts with TTI > 14 days had longer median OS compared with those treated within ≤14 days (16.4 vs 10.1 months), with improved OS on unadjusted analysis (HR 0.69, 95% CI 0.50–0.96; p = 0.028), though this association was not statistically significant after multivariable adjustment (HR 0.74, 95% CI 0.53–1.05; p = 0.097). Pts with TTI > 14 days also had longer median PFS compared with ≤14 days (6.5 vs 4.8 months), with improved PFS on unadjusted analysis (HR 0.67, 95% CI 0.51–0.88; p = 0.0038). On multivariable analysis, TTI > 14 days remained independently associated with improved PFS (HR 0.75, 95% CI 0.56–1.00; p = 0.047). However, when analyzed as a continuous variable, TTI was not independently associated with OS (HR 0.99, 95% CI 0.98–1.00; p = 0.173) or PFS (HR 0.99, 95% CI 0.98–1.00; p = 0.089). Conclusions: In this multicenter cohort of pts with metastatic EP-NEC, earlier initiation of systemic therapy (≤14 days) was not associated with improved overall survival, and longer time-to-treatment was independently associated with improved PFS. However, when TTI was analyzed as a continuous variable, no statistically significant associations were observed, suggesting that the observed benefit with delayed treatment may reflect pt selection or clinical context rather than a direct biological effect. These findings may provide reassurance in scenarios where short delays are necessary—for biomarker testing or clinical trial enrollment—and highlight the need for further investigation in the era of precision oncology.

1557 Background: Immunotherapy is now a standard-of-care treatment for lung cancer across most stages. Access to immunotherapy and molecular diagnostic tests in conflict-affected countries such as Syria remains poorly described. As the principal cancer center in Syria, Al-Bairouni University Hospital (ABUH) provides care for nearly three-quarters of all cancer cases nationally. We conducted this study to evaluate access to immunotherapy and molecular diagnostic services at ABUH. Methods: A mixed-methods study was performed between 2022 and 2024 at ABUH. This study included a retrospective cohort of all patients diagnosed with lung adenocarcinoma. Quantitative data included disease stage at diagnosis, molecular testing rates, and immunotherapy utilization. In addition, a qualitative patient survey was thematically analyzed to explore barriers to treatment access in a separate cohort of patients with mixed tumor types. Results: Among 2,920 patients diagnosed with lung cancer, 1,393 (47.7%) had lung adenocarcinoma. The median age at diagnosis was 61 years; 79.7% of patients were male. Smoking history was as follows: Current 792 (56.9%), Former 268 (19.2%), never smoked 318 (22.8%) At presentation, 3 patients (0.2%) had stage I disease, 40 (2.9%) stage II, 174 (12.5%) stage III, and 778 (55.8%) stage IV disease, staging was unknown for the rest of the patients. EGFR mutation testing was performed by ABUH for 226/1393 patients (16.2%) only, with positive results identified in 124 cases (8.9%). PD-L1 testing was conducted by ABUH in only 32/1393 patients (2.3%) and was positive in 23 (1.65%). Of all patients with lung adenocarcinoma, only 5 patients (0.6%) with stage IV disease received immunotherapy. All were treated with nivolumab. Thematic analysis of qualitative data (35 patients) revealed that high treatment costs and limited drug availability are the primary barriers to accessing immunotherapy. Conclusions: This study represents the first evaluation of access to immunotherapy for patients with lung cancer in Syria. Even at ABUH, the country's main cancer center, access to immunotherapy and molecular testing remains markedly limited. International collaboration is necessary to expand diagnostic infrastructure, standardize data reporting, and enhance financial protection mechanisms. These are critical steps toward achieving better cancer care in Syria.

Background. Solid organ transplant recipients (SOTRs) are at heightened risk for cardiovascular implantable electronic device-related complications, particularly infection, because of chronic immunosuppression and comorbidities. Although leadless pacemakers (LPs) reduce infection risk by eliminating transvenous leads and generator pockets, adoption in SOTRs has remained limited, largely because earlier systems were restricted to single-chamber ventricular pacing and lacked physiologic atrioventricular synchrony. The helix-fixation Aveir LP platform enables atrial, ventricular, and dual-chamber leadless pacing, but clinical experience in transplant recipients remains limited. Methods. We conducted a retrospective, multisite analysis across an integrated health system, identifying all adult SOTRs who underwent Aveir LP implantation between January 2022 and October 2025. Clinical characteristics, transplant details, pacing indications, device configuration, procedural outcomes, and follow-up data were collected. Primary outcomes included procedural success, complications, and device-related infection. Secondary outcomes included pacing performance, need for system revision or upgrade, and early device durability. Results. Thirteen SOTRs (mean age 64 ± 15 y; 15% female) underwent Aveir LP implantation, including atrial (n = 4), ventricular (n = 5), and dual-chamber (n = 4) systems. Transplanted organs included heart (46%), lung (31%), kidney (38%), and liver (15%), with 31% having multiple organ transplants. Over half of patients were critically ill at implantation, and 46% were dialysis-dependent, representing a high-risk cohort. All procedures were acutely successful with no intraprocedural complications. During a median follow-up of 258 d (interquartile range, 216–641 d), no device-related infections occurred. Electrical performance remained stable, with 1 atrial device replacement at 2.5 y for elevated capture thresholds. Conclusions. In a high-risk population of SOTRs, atrial and atrioventricular synchronous leadless pacing using the Aveir platform was feasible, achieved high acute procedural success, and demonstrated favorable early safety signals, including absence of device-related infection over available follow-up. Larger studies with longer-term follow-up are needed to define durability and long-term outcomes.

Background: Loeys–Dietz syndrome (LDS) is an autosomal dominant aortopathy characterized by aggressive aneurysm formation and arterial dissections. Pregnancy-related outcomes and timing of LDS diagnosis remain poorly characterized. Methods: Demographics, genetic, obstetric, and vascular data was collected from genetically or clinically confirmed individuals with LDS seen at the three Mayo Clinic sites from 2018 to 2025. Aneurysm progression, new aneurysm formation, and arterial dissections were recorded across all vascular beds. Vascular events were assessed during pregnancy, within 12 months postpartum, and during breastfeeding. Comparative analyses were performed between women with and without a history of pregnancy, and a single-arm descriptive analysis was conducted among patients who experienced vascular complications during the peripartum period. Continuous variables were compared using the Mann–Whitney U test, while categorical variables were analyzed using chi-square or Fisher exact tests. Results: Of 47 women with LDS, 24 had a history of pregnancy, accounting for 54 pregnancies. In the comparative analysis, age at LDS diagnosis differed significantly between women with and without a prior pregnancy: women without prior pregnancy were diagnosed at a younger age (median 23.5 years [IQR 10.8–41.0], n = 23) than those who had been pregnant (median 53.5 years [IQR 43.0–59.3], n = 24). Among pregnant women, the median age at first pregnancy was 28 years (IQR 23–34); only 4 (16.7%) knew their diagnosis before pregnancy. Of 54 pregnancies, 40 (74.1%) resulted in live birth, with 23 (57.5%) vaginal and 17 (42.5%) cesarean deliveries; preterm delivery occurred in 1 (2.5%) pregnancy, and postpartum hemorrhage in 2 (5.0%). No maternal deaths, aortic dissections, or uterine ruptures occurred during gestation or the first postpartum year. In addition, 14 women (58.3%) developed aneurysms, 6 (25.0%) experienced at least one arterial dissection, and 7 (29.2%) required surgical repair, predominantly involving the ascending and abdominal aorta. The prevalence of vascular complications did not differ significantly between groups. Conclusions: In this LDS cohort, pregnancy and the early postpartum period were not accompanied by acute aortic catastrophes, despite frequent diagnostic delay. Although women without prior pregnancy were diagnosed at a younger age, the overall burden of vascular and morphologic complications did not differ significantly by pregnancy history. These findings highlight the importance of long-term cardiovascular follow-up in women with LDS.

837 Background: A recent randomized trial suggested that CR may influence ICI activity in patients with lung cancer. However, the same has not been established in GI cancers, where reports have shown mixed results with variable definitions of 'early' vs 'late' IT. We evaluated multiple approaches to assess the impact of CR on first-line ICI in GI malignancies. Methods: This retrospective study included patients from three Mayo Clinic sites (N=455). Both previously reported IT cutoffs and a new cutoff derived from ROC analysis were evaluated. Patients were categorized by the median of all ITs, the median of the first four ITs, and whether ≥20% of ITs occurred before the identified cutoff. Univariate and multivariate Cox regression (adjusting for age, MSI status, type of cancer, metastasis status, number of cycles, and receipt of chemotherapy with ICI) assessed associations with OS. KM analyses were performed to illustrate survival differences. The primary endpoint was OS. Results: When patients were categorized based on whether ≥20% of infusions occurred before 14:00 (ROC-derived cutoff), a significant association with OS was observed. On univariate analysis, early infusion timing was associated with improved survival (HR 2.30, 95% CI 1.58–3.32, p <0.001). This remained significant after multivariable adjustment (HR 2.11, 95% CI 1.41–3.16, p < 0.001). Median OS was 14.2 months in the early group vs 3.8 months in the late group (log-rank p < 0.001). Using previously defined cutoffs, categorization by the median IT of all infusions or the median of the first four infusions did not demonstrate a significant association with OS in either univariate or multivariate Cox regression analyses. Conclusions: These findings highlight the potential role of infusion timing as a chronotherapy factor in GI cancers. Given the retrospective design and heterogeneous population, prospective studies are warranted to validate this signal and clarify its clinical relevance. Baseline demographics of patients by infusion timing (early vs late). Variables Early N=412 (%) LateN=43(%) Total N=455(%) p-value Age <70 249(60.4) 21(48.8) 270 (59.3) 0.1 >70 163(39.6) 22(51.2) 185 (40.7) Gender F 118(28.6) 16(37.2) 134 (29.5) 0.3 M 294(71.4) 27(62.8) 321 (70.5) Cancer Type Gastroesophageal 109 (26.5) 8 (18.6) 117 (25.7) 0.1 Hepatocellular 159 (38.6) 24 (55.8) 183 (40.2) Biliary 86 (20.9) 4 (9.3) 90 (19.8) MSI-H 58 (14.1) 7 (16.3) 65 (14.3) Metastasis No 150 (36.4) 22 (51.2) 172 (37.8) 0.1 Yes 262 (63.6) 21 (48.8) 283 (62.2) Immunotherapy Cycle Number <6 189 (45.9) 33 (76.7) 222 (48.8) <0.001 >6 223 (54.1) 10 (23.3) 233 (51.2)

619 Background: Well-differentiated G3 GEP-NETs are rare and heterogeneous diseases, limiting phase III trials and definition of clear standards of care. Building upon our preliminary cohort of 76 patients (pts), we present an updated and expanded retrospective analysis across three Mayo Clinic tertiary centers. Methods: We included pts with histologically confirmed well-differentiated G3 GEP-NETs diagnosed since 2017 (new WHO classification) from the three Mayo Clinic sites (Rochester, Phoenix, Jacksonville). Endpoints were ORR, DCR, PFS, and OS across treatment lines. PFS/OS were estimated by Kaplan-Meier. OS was defined from treatment start. Multivariate Cox regression was used to evaluate the association of clinic-pathologic features (age, sex, tumor functionality, Ki-67, primary tumor site, stage at diagnosis, presence of liver metastasis, number of metastatic sites at diagnosis) with OS (p<0.05). Results: 111 pts (median age 62 y, range 22–83). Primary sites were pancreas (58%), small bowel (19%), unknown (9%), and rectum (5%). Most tumors were G3 at diagnosis (88%); the remainder evolved from prior G1/G2. Ki-67 was 20–55% in 83% of cases. Most were nonfunctional (70%); functional subtypes included carcinoid (13%) and gastrinoma (8%). Median plasma 5-HIAA was 38.5 ng/ml (5–1394). Advanced disease was present in 85%. Common metastatic sites included liver (85%), lymph nodes (32%), bone (26%), peritoneum (10%), and lung (9%). Median number of metastatic sites was 1 (range 0–5). Median number of systemic treatment lines was 2 (range 0–8). The most frequent regimens and outcomes are shown in the Table. Insulin-secreting tumors (HR 2.16, 95% CI 1.33–25.73, p=0.019) and ≥2 metastatic sites (HR 2.13, 95% CI 1.05–4.31, p=0.035) were associated with inferior OS. Conclusions: This represents one of the largest real-world datasets of well-differentiated G3 GEP-NETs and provides a deeper evaluation of treatment strategies and prognostic factors. CAPTEM, SSAs, and PRRT with Lu-177 emerged as the most commonly used therapies, with PRRT showing the most favorable outcomes. Insulin secretion and higher metastatic burden were confirmed as adverse prognostic factors. CAPTEM SSAs PRRT Lu-177 Carboplatin plus etoposide FOLFOX Everolimus Sunitinib N of pts (%) 64 (58) 44 (40) 37 (33) 24 (19) 18 (13) 11 (10) 8 (7) Line of therapy (%) First 36 (56.3) 27 (61.4) 5 (13.5) 13 (59.2) 5 (7.2) 1 (9.0) 1 (12.5) Second 15 (23.4) 13 (29.5) 13 (35.2) 3 (13.6) 5 (35.7) 3 (27.3) 2 (37.5) Third or higher 13 (20.3) 4 (9.1) 19 (51.3) 6 (27.2) 8 (57.1) 7 (63.7) 5 (62.5) DCR (%) 60.9 56.8 75.0 52.2 71.4 45.5 37.5 ORR (%) 34.4 13.6 44.4 30.4 35.7 18.2 12.5 mPFS (95% CI) 8.0 (5.3-10.6) 6.2 (2.8-9.5) 11.2 (9.1-13.3) 7.3 (2.8-11.8) 4.4 (2.4-6.4) 3.9 (2.2-5.6) 3.9 (1.54-6.26) mOS (95% CI) 40.1 (23.0-57.2) 50 (22.6-77.4) 76.1 (16.3-135.8) 33.0 (21.0-45.0) 21.1 (15.0-27.2) NE NE

Pleomorphic adenoma of the breast is a rare tumor, with fewer than 100 patients described in the English literature, mainly as case reports and small case series. Histologically, breast pleomorphic adenoma resembles its more common salivary gland counterpart; however, it can present diagnostic challenges, particularly on core needle biopsy and fine-needle aspiration. The differential diagnosis includes benign and malignant tumors, which carry major treatment implications, from the extent of surgical intervention to the potential use of chemotherapy. Herein we describe a tumor that was initially diagnosed as a triple-negative matrix-producing metaplastic carcinoma, but a secondary review led to the diagnosis of pleomorphic adenoma of the breast. Prior to the secondary review, the patient underwent an excisional biopsy, sentinel lymph node biopsy, and one round of chemotherapy. This report adds to the limited literature surrounding this entity and discusses the differential diagnosis along with histopathologic and immunohistochemical findings that aid in the diagnosis and reviews the radiologic findings observed throughout the patient's clinical course. This patient underscores the difficulty of diagnosis and highlights the need for multidisciplinary consideration and communication to avoid overtreatment.

Background: Left atrial (LA) strain is a marker of atrial myopathy and remodeling. While echocardiographic LA strain is increasingly used to assess atrial function, the prognostic value of change in LA strain before and after catheter ablation (CA) for atrial fibrillation (AF) remains underexplored. Objective: To evaluate the association between quartiles of LA strain parameters—including pre-ablation strain, post-ablation strain, and change in strain—with atrial fibrillation recurrence, stratified by ejection fraction (EF). Methods: This retrospective study encompassed AF patients who underwent their first CA at Mayo Clinic Arizona from Oct 2018 to Feb 2022. Transthoracic echocardiography parameters, including the three LA strain (LAS) phases—contraction, conduit, and reservoir—were collected using TOMTEC software on the closest date before the CA procedure. Logistic regression analysis was used to evaluate the association between LAS parameters and AF recurrence post-CA, adjusted for clinical covariates including age, gender, hypertension, diabetes, coronary artery disease, dyslipidemia, obstructive sleep apnea, thromboembolism, TIA/stroke, chronic kidney disease, and AF type. Results: Out of 335 patients who underwent CA, 222 had both pre- and post-ablation LA strain data. Among these, 71 of 222 patients (31.98%) experienced AF recurrence after CA. The mean age at time of procedure was 66.9 ± 10.3 years; 150 (67.57%) were male, and 83 (37.39%) had persistent AF. Significant associations were observed between specific quartiles of LA strain and AF recurrence. In patients with EF >50%, Q4 of contraction strain change (pre- vs. post-ablation) was strongly associated with increased recurrence risk (OR 8.80; 95% CI 1.80–42.98). Similarly, post-ablation contraction strain Q4 was associated with higher recurrence in both the overall group (OR 6.36; 95% CI 1.47–27.53) and the EF>50% subgroup (OR 8.80; 95% CI 1.80–42.98). In contrast, reservoir strain change Q2 (OR 0.10; 95% CI 0.01–0.86), and post-ablation reservoir strain Q3 (OR 0.09; 95% CI 0.01–0.69) and Q4 (OR 0.10; 95% CI 0.02–0.70) were protective. Conclusions: Greater increases in contraction strain post-ablation and higher post-ablation contraction strain were strongly associated with AF recurrence, particularly in those with preserved EF. Conversely, favorable reservoir strain post-ablation was protective. LA strain may offer key prognostic value in risk-stratifying AF patients undergoing ablation.

Background: Cardiac amyloidosis (CA) patients with reduced left ventricular ejection fraction (EF) are at increased risk for mortality. The benefit of cardiac resynchronization therapy (CRT) in terms of mortality reduction has not been established in this population. Aim: To evaluate the survival benefit of CRT, either CRT-D or CRT-P, in a large cohort of patients with cardiac amyloidosis and reduced EF. Methods: We retrospectively analyzed patients with confirmed CA and reduced EF (<40%) between 2009 and 2023 across Mayo Clinic sites. Patients were stratified into three groups: no device, CRT with pacemaker function (CRT-P), and CRT with defibrillator function (CRT-D). CRT devices were indicated for low ejection fraction less than 40% and patients who had chronic heart failure with a wide QRS. Kaplan-Meier survival estimates were generated, and log-rank tests were used for comparison. A secondary analysis was conducted combining CRT-P and CRT-D versus no device (EF <40%), and a tertiary analysis compared CRT-P versus CRT-D. Results: Among 184 patients [36 AL (20%), 148 ATTR (80%)], 38 (19%) had no cardiac device and EF <40%, 20 (11%) received CRT-P, and 116 (63%) received CRT-D. The median follow-up was 3.4 years (1.7, 5.0). The probability of survival was significantly higher in the CRT group compared to the no device-EF<40 group (Log Rank p=0.013; figure B). Among patients receiving CRT, there was no significant difference in all-cause mortality between those receiving CRT-P and those receiving CRT-D (Log Rank p=0.5; figure C). Conclusion: In patients with cardiac amyloidosis and reduced EF, CRT is associated with significantly improved survival compared to no device. No mortality difference was observed between CRT-P and CRT-D. Prospective studies are warranted.

Introduction: Vascular Ehlers-Danlos syndrome (vEDS) is a rare connective tissue disorder caused by pathogenic variants in the COL3A1 gene, often leading to arterial, intestinal, and uterine rupture. While vascular complications are well-documented, the prevalence and characteristics of cardiac arrhythmias in this population remain underexplored. Aim: To assess the prevalence of arrhythmias and conduction abnormalities in patients with confirmed vEDS. Methods: A retrospective cohort study was conducted across all three Mayo Clinic sites. Patients with vEDS were initially identified using an electronic data extraction tool. Each case was subsequently confirmed through detailed chart review. Additional reviews were performed to assess the prevalence of heart blocks and both atrial and ventricular arrhythmias. Statistical analysis was conducted using SPSS to determine the prevalence of each arrhythmia type. Results: A total of 132 patients with confirmed vEDS were included in the study. The mean age was 45.7 ± 13 years. The cohort was predominantly white (93.7%), with 47 males (35.6%) and 85 females (64.4%). Atrial arrhythmias were identified in 15 patients (11.4%), including atrial fibrillation in 14 (10.6%) and atrial flutter in 8 (6.1%). Supraventricular tachycardia (SVT) was observed in 15 patients (11.4%). Conduction abnormalities included first-degree AV block in 8 (6.1%), second-degree AV block in 3 (2.3%), left bundle branch block in 8 (6.1%), and right bundle branch block in 15 (11.4%) patients. Ventricular arrhythmias were observed in 6 patients (4.5%) with sustained ventricular tachycardia, 6 (4.5%) with non-sustained ventricular tachycardia, and 7 (5.3%) with ventricular fibrillation. Postural orthostatic tachycardia syndrome (POTS) or orthostatic hypotension was documented in 18 patients (13.6%). Conclusion: Although arrhythmias are not the most common manifestation of vEDS, their prevalence in this cohort is notably higher than in the general population and tends to occur at a younger age. These findings support the consideration of routine screening for atrial and ventricular arrhythmias in patients with vEDS as part of their long-term cardiovascular management.